Spin-On Diffusants Catalog 6

Revision #6, July 2004

FILMTRONICS INC., BOX 1521, BUTLER PENNSYLVANIA 16003 U.S.A. TEL: (724) 352-3790 E-MAIL: [email protected] 1 -

SPIN-ON DIFFUSANTS

INTRODUCTION

Spin-on dopants (SOD) provide an impurity source for semiconductor junction fabrication. Filmtronics spin-on dopants permit precise control of dopant entering the silicon through application of a homogeneous solution to the substrate. Advantages of this method of diffusion are:

1. Uniform solutions manufactured with statistical process control. 2. Convenient application of dopant with non hygroscopic solutions. 3. Uniform and consistent doping with high yields. 4. Extended quartz tube life. 5. Simultaneous diffusion of “P” and “N” types and simultaneous

diffusion of different concentrations of the same dopant. 6. No storage of source wafers or use of costly ion implant

equipment. Dopants are available in both “P” and “N” types, pure (SiO2) glass film, and lifetime modifiers. Basic steps in spin on methods are as follows:

1. Pre-diffusion cleaning of silicon substrate wafer. 2. Application of dopant to substrate followed by spinning manually

or automatically (a typical speed is 2000 to 6000 rpm). For approximately 5 seconds.

3. Some solutions require a pre-diffusion bake to remove excess solvent.

4. Diffusion at an elevated temperature to yield desired sheet resistivities and junction depth.

5. Post diffusion clean up – dilute HF.

AVAILABILITY

Dopant solutions are available in varied concentrations to suit the user’s particular requirements. Shipments are from stock and are generally initiated the same day as orders are received.

“P” TYPE DOPANTS Aluminum Film – Product Code 100 - Used for power semiconductor junctions; (SCR, Transistor, etc.). Solutions are also available to diffuse aluminum boron, and aluminum gallium in a one-step simultaneous diffusion. Boron Film (SiO2) – Product Code 150 - Available in a variety of concentrations to produce a boron diffused junction with a minimum amount of surface damage. May be used to produce SCR’s, IC’s, Transistors. Poly Boron Film – Non hygroscopic solution used to diffuse a high concentration of boron into silicon with no surface damage and no pre bake of wafer required. Just spin-on, load in quartz boat and diffuse. Boron Film – Product Code 200 - Produces a high concentration boron source for production of “P” layers in zener diodes, rectifiers, and other devices. Gallium Film (SiO2) – Product Code 250 – Used in production of SCR’s and power transistors. Solutions are available to diffuse gallium and boron or gallium and arsenic simultaneously for one-step diffusion of PP+ or NP junctions in silicon wafers.

“N” TYPE DOPANTS Antimony Film (SiO2) – Product Code 300 – A contaminant free source for the N+ diffusion of buried collector layer in bipolar semiconductor devices. Sheet resistivities available from 10 to 300 Ω/ Arsenic Film (SiO2) – Product Code 350 - Used in production of buried collector regions in linear and digital bipolar devices, V-mos, N-mos and some solar cell designs. Provides excellent uniformity, minimum surface damage and impurities. Sheet resistivities from 5 to 300 Ω/ are available. Phosphorous Film (SiO2) – Product Code 500 – Provides an “N” type junction with a minimum amount of surface damage. May be utilized in the fabrication of rectifiers, NPN devices and emitter diffusion. Also available with an impurity source, such as Fe, Pt, or Au, to simultaneously diffuse a lifetime modifier. Phosphorous Film – Product code 450 – A high concentration phosphorous source for rectifier production. Sheet resistivities available from 0.5 to 20 Ω/ depending on diffusion time and temperature.

LIFETIME MODIFIERS Gold Film – Product Code 900 – Produces a thin film of gold upon pyrolysis which may act as a diffusant source for fast switch rectifiers. Gold Film(SiO2) – Product Code 910 – Collodial suspension of gold in SiO2 for control of minority lifetime. Platinum Film – Product Code 920 – Produces a thin film of platinum upon pyrolysis for contact Schottky diodes and as a diffusant for fast switch rectifiers. Platinum Film (SiO2) – Product Code 930 – Collodial suspension of platinum in SiO2 for control of minority lifetime.

PASSIVATION FILM (SIO2) (SiO2) Film – Product Code 700A and 700 B – Yields an impurity tree glass layer which may be used for passivation, diffusion masking, planarization of uneven wafer topologies, intermediate layer in a trilayer photoresist process for optical, electron beam, or x-ray lithography. The pyrolyzed film may be removed selectively by dilute HF solution or buffered oxide etchants. Photolithographic techniques may be employed. Type 700B yields a thicker film that 700A.

DIFFUSANTS FOR GaAs, GaAsP, GaP Zinc Film – Product Code 980 – Used to diffuse Zinc in GaAs, GaP and GaAsP for L.E.D.’s and other devices. Indium Film – 990 Tim Film – 970 Cadmium Film – 960 Selenium Film – 965 Many other (SOD) formulations available upon request. Neodymium Titanium Yttrium Lanthanum Strontium Copper Iron Cerium Barium

PRODUCT INFORMATION


CONTENTS PRODUCT INFORMATION

(a)SHELF LIFE, HANDLING, PACKAGING

(b)SAFETY & ENVIRONMENTAL ISSUES

PRODUCT APPLICATION NOTES

(a)EQUIPMENT USED

(b)PROCEDURE FOR APPLICATION

TROUBLE SHOOTING

(a)CAUSE AND EFFECT WITH POSSIBLE SOLUTIONS

PRODUCT DESCRIPTION

(a)SUMMARY OF ALL PRODUCTS

(b)POTENTIAL APPLICATIONS

QUALITY CONTROL & EQUIPMENT

(a)FABRICATION Q.C.

DOPANT ATOM PROPERTIES

PRODUCT PRICING

PRODUCT INFORMATION


SPIN-ON DOPANT CONCENTRATIONS

SOLUTION %DOPANT COMPOUND

%SiO2 POTENTIAL APPLICATION

Al 100 Al 8.0 0.0 SCR AIB 120 Al 4.0 B 4.0 0.0 Transistor, Rectifier

AIB 120 A Al 1.7 B 7.0 0.0 Transistor, SCR Al 110 Al 1.6 8.0 SCR, Power Discretes, Guard Ring Al 111 Al 1.0 0.0 Rectifier

AlGa 130 Al 1.3 Ga 1.3 13.0 SCR

Sb 300 Sb 3.2 3.1 I.C. Sb 301 Sb 3.2 2.2 I.C. Sb 302 Sb 3.5 2.2 I.C. Sb 303 Sb 4.1 2.1 I.C.

As 350 As 0.5 2.1 Resistor As 351 As 0.7 2.5 Buried layer As 352 As 1.0 3.3 Buried layer As 353 As 1.54 5.0 MOS As 354 As 2.0 4.2 MOS

B200 B 8.0 0.0 Rectifier, SCR B200B B 7.0 0.0 Rectifier, SCR B201 B 6.0 0.0 Rectifier, SCR B202 B 5.0 5.0 Rectifier, SCR B203 B 4.5 5.0 Rectifier, SCR

B150 B 0.4 5.0 I.C. B151 B 1.0 5.0 I.C. B152 B 1.5 5.0 I.C. B153 B 2.0 0.0 I.C. B154 B 3.8 0.0 I.C., Base/Isolation DiscretesB155 B 4.0 0.0 Base-resistor, Isolation Discretes

Ba 250 Ga 2.0 7.2 SCR Ga 252 Ga 1.5 7.2 SCR Ga 254 Ga 1.0 7.2 SCR GaB 260 Ga 2.0 B 7.0 0.0 Transistor, Rectifier

P450 P 33 0.0 Recitifier, SCR P451 P 27 0.0 Recitifier, SCR P452 P 15 0.0 Recitifier, SCR

P 500 P 0.08 8.0 Base I.C. P 501 P 0.2 8.0 Resistor-Base, I.C. P 502 P 0.24 8.0 Resistor-Base, I.C. P 503 P 0.3 8.0 Resistor-Base, I.C. P 504 P 0.5 8.0 Resistor-Base, I.C. P 505 P 1.0 6.0 Resistor-Base, I.C. P506 P 3.0 6.0 Emitter, I.C. P 507 P 4.0 5.0 Emitter, I.C. P508 P 8.0 5.0 Emitter, I.C. P 509 P 15 5.0 Solar Cells

AuP 540 Au 2.0 P 3.0 6.0 Emitter Diffusion Au 900 Au 3.0 0.0 Au 910 Au 2.7 6.0 Minority Carrier

PRODUCT INFORMATION


SOLUTION %DOPANT COMPOUND

%SiO2 POTENTIAL APPLICATION

Pt 920 Pt 3.0 0.0 Pt 930 Pt 2.7 6.0 Minority Carrier

Si 700A 0.0 6.0 Passivation – Liquid Crystal Si 700B 0.0 10.8 Planarization, Growth Mask

Cd 960 2.0 6.0 GaAs Se 965 2.0 6.0 GaAs Sn 970 8.0 6.0 GaAs Zn 980 2.0 5.9 GaAs

Other Formulations Available Upon Request

PRODUCT INFORMATION


ADDITIONAL DOPANT COMPOSITIONS

AVAILABLE TYPE COMPOSITION CONCENTRATION SHELF LIFE

%SiO2/Gram Cmpd. Per 100ml (Months at 4˚C)

P-Si-Film

P-59250 5.9 5.0 P-High 3 P-59230 5.9 3.0 P-High 3 P-59210 5.9 1.0 P-High 3 P-59350 5.9 0.5 P-Medium 3 P-59310 5.9 0.1 P-Medium 3 P-59450 5.9 0.05 P-Low 3 P-59410 5.9 0.01 P-Low 3 P-59550 5.9 0.005 P-Lowest 3 P-59510 5.9 0.001 P-Lowest 3

Sb-Si-Film

Sb-59220 5.9 2.0 Sb-High 2 Sb-59215 5.9 1.5 Sb-High 2Sb-59210 5.9 1.0 Sb-High 2Sb-59350 5.9 0.5 Sb-Medium 2Sb-59320 5.9 0.2 Sb-Medium 2Sb-59310 5.9 0.1 Sb-Medium 2Sb-30230 3.0 3.0 Sb-High 2Sb-30210 3.0 1.0 Sb-High 2Sb-20220 2.0 2.0 Sb-High 2Sb-10220 1.0 1.0 Sb-High 2

Pt-Si-Film

Pt-59210 5.9 1.0 Pt-High 3 Pt-59350 5.9 0.5 Pt-Medium 3 Pt-59320 5.9 0.2 Pt-Medium 3

B-Si-Film

B-59210 5.9 1.0 B-High 3 B-59350 5.9 0.5 B-Low 3 B-59320 5.9 0.1 B-Low 3

Si-Film

Si-11000 11.0 3 Si-85000 8.5 3 Si-59000 5.9 3 Si-40000 4.0 3 Si-30000 3.0 3 Si-20000 2.0 3

PRODUCT INFORMATION


ADDITIONAL DOPANT COMPOSITIONS

AVAILABLE TYPE COMPOSITION CONCENTRATION SHELF LIFE

%SiO2/Gram Cmpd. Per 100ml (Months at 4˚C)

Au-Si-Film

Au-59210 5.9 1.0 3 Au-59310 5.9 0.1 3 Au-59350 5.9 0.5 3 Au-40210 4.0 1.0 3 Au-40350 4.0 0.5 3 Au-30210 3.0 1.0 3

Zn-Si-Film

Zn-59220 5.9 2.0 Zn-High 2 Zn-59210 5.9 1.0 Zn-High 2 Zn-59350 5.9 0.5 Zn-Medium 2

Ga-Si-Film

Ga-59225 5.9 2.5 Ga-High 3 Ga-59220 5.9 2.0 Ga-High 3 Ga-59215 5.9 1.5 Ga-High 3 Ga-59210 5.9 1.0 Ga-High 3 Ga-59310 5.9 0.1 Ga-Low 3

As-Si-Film

As-59240 5.9 4.0 As-High 3 As-59216 5.9 1.6 As-High 3As-59215 5.9 1.5 As-High 3As-59210 5.9 1.0 As-High 3As-59350 5.9 0.5 As-Medium 3As-59340 5.9 0.4 As-Medium 3As-59310 5.9 0.1 As-Medium 3

As-59240-S 8.0 4.0 As-High 3As-59235-S 8.0 3.5 As-High 3As-59214-S 8.0 1.4 As-High 3As-59213-S 5.0 1.3 As-High 3

PRODUCT INFORMATION


FILMTRONIC SPIN-ON DOPANTS

GENERAL INFORMATION Container Size of Dopants – Dopants are supplied generally in 125 ml, 500 ml, and 1 liter containers. Other sizes may be supplied at the customer’s request. Shipping is made via air with ground transportation optional.

Storage – Shelf life of materials are generally 3-6 months or more at 2˚C to 4˚C. Dopant solutions should be stored in a refrigerated ambient for optimum shelf life. Solutions should be allowed to reward to room temperature before spinning on wafers. Always allow the SOD to acclimate for 24 hours at room temperature before spinning.

Handling Instructions – Materials are flammable, with some flash points as low as 60˚C. Therefore, adequate precautions should be exercised. Appropriate ventilation steps are also necessary to facilitate spin depositions while minimizing any health hazards. Spin-on dopants may produce skin irritations or eye burns. Goggles should be worn if there is danger of splashing. If the liquid or mist comes in contact with the skin or eyes, immediately wash with water for at least 15 minutes; in case of eye contact, get medical attention. Consult the MSDS.

Substrate Preparation – Any acceptable prediffusion cleaning method may be used. We recommend use of a 15 min. soak at 80˚C using a 4 to 1 (by volume) H2SO4 – H2O2 solution to remove any organic contaminants, a water rinse, followed by a 10 to 1 (by volume) H2O – HF soak with appropriate final water rinses to remove any oxide or contaminants, isopropanol rinse and spin dry. After surface treatment, the wafers are positioned on the spinner, a few drops of solution are applied to the center of the wafer and spinning is begun. About 10-15 seconds of spinning is sufficient to provide uniform looking oxide film.

Application – Dopants may be appliled via automatic dispensing equipment or polyethylene droppers in a manual mode. Uniformity and consistency of coatings is optimized with an accurate automatic application process. The coating volume required on a 3” diameter wafer is 1-2ml per wafer. The time interval between dispense and spin out should be consistent from wafer to wafer. Spinner lines should be kept clean and fee of particulate material. Optimum conditions for application and spinning of dopant are a spin speed of 2000-6000 rpm at 35%-40% relative humidity and a temperature of about 67˚-73˚F (at the spinner). A problem of cloudiness occasionally can occur if humidities exceed the above values shile spinning. Diffusion accordingly suffers from these conditions. The fab area should be optimized to control the humidity and temperature. Temperature and humidity control changes over the spinner cup work well if the fab environment cannot be controlled easily.

Post Bake Wafers – Spun wafers may be hygroscopic depending on solution used. The coated wafers may be heat treated to eliminate the spun film’s affinity for water. (Water pick up is visually detected if films become cloudy in appearance.) A heat treatment on a hot plate (after spinning) at 100˚-200˚C for 15 minutes precludes the adverse condensation, unless the wafer is exposed for a long time to high RH ambient.

Ventilation – All spinner ventilation should be positive and away from the operator. However, excessive drafts directly across the spinner-heads should be minimized to prevent premature evaporation of the dispensed spin-on liquid puddle, before the liquid is spun-out as a film.

Production – Filmtronics, spin-on dopants are produced in compliance with U.S. Government regulations with respect to the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA).

Disposal – Unsused SOG’s may be sent back to us for disposal or can be disposed of by incineration or a competent environmental waste disposal firm.

All statements, information and data given herein are believed to be accurate and reliable but are presented without guaranty, warranty or responsibility of any kind, expressed or implied. Statements or suggestions concerning possible use of our products are made without representation or warranty that any such use is free of patent infringements and are not recommendations to infringe any patent. The user should not assume that all safety measures are indicated or that other measures may not be required.



SPIN-ON AND CURE OF SOD

This application note describes the general procedures and guidelines for spinning high quality films from Filmtronics materials and their optimal cure.

Spin-On Equipment Filmtronics’ materials differ significantly form the other spin-on materials used in wafer fabrication technology such as photoresists and polyimides. The SOD solutions have much lower viscosities (1 to 10cP), more volatile solvents and are sometimes acidic. When the solvent(s) (primarily alcohol and ketones) evaporate, as the wafer is spun, an insoluble residue (silicate) is produced which may form a fine silicate dust. This dust can be a major source of particulates. These properties of the SOD may result in several application problems associated with SOD films:

A. Due to its low viscosity, the SOD solution tends to form a mist of liquid droplets above the substrate during the spin which may give rise to particles or bubble-like defects in the films if not spun properly.

B. Insoluble SOD deposits, formed by evaporation of SOD on the various surfaces in the spinner, may flake

off, resulting in particulate defects in the films.

C. The mildly acidic nature of the SOD solution may cause gradual corrosion of exposed metal surfaces. Metal components should not directly contact the acidic SOD.

It is important that the spinner employed for application of SOD films must be equipped to provide, a controllable downward exhaust in the spinner bowl area to prevent the mist from settling on the substrates. A means of rinsing after each wafer should also be provided to thoroughly rinse the dispense nozzle, spinner bowl, and other non-metallic components of the spinner (i.e. chuck) to prevent build-up of SOD residues. Non-metallic components should be constructed of Teflon except for the chuck that should be constructed of Delrin, Kel-F, PE, or P.E.E.K. Although any photoresist spinner can be modified for SOD use, it is recommended that the user consider the purchase of an “SOD Coater” - a spinner designed specifically for SOD processing. In addition to incorporating the above mentioned features, the SOD coaters offer many other useful features to insure consistently defect-free films of high uniformity. These include:

1. A controllable cup exhaust. It is advisable that the cup exhaust be on during all process steps. It is necessary that the exhaust be adequate to remove the solvent vapor and keep the mist generated during the spin process below the plane of the silicon surface.

2. A gauge to monitor exhaust vacuum. A typical cup exhaust flow may be 20mm to 40mm of water. The

exhaust on different brands of spin coaters may vary, they could be in liters per minutes, mm of water or mm of mercury. The units are insignificant, what is most important is that the exhaust be kept constant to maintain the best process control. The cup exhaust affects the spin cup temperature which affects the film thickness and may yield variations in sheet resistivities. A warm environment for the spinner cup will yield a thicker film due to rapid solvent evaporation from the SOD. The cabinet exhaust must be adequate enough so that as the machines reach operating temperature the cabinet and spinner cup stay at the same temperature. The cabinet exhaust should ventilate the SOD delivery system and the cabinet while maintaining a uniform temperature.

3. Humidity control of the spin area via a nitrogen blanket. 4. The spinner cup should be of PVC or high density polypropylene or polyethylene as these materials are



compatible with SOD’s. The spinner cup should have a programmable solvent rinse capability. The cup rinse programmed into your spinning cycle will wet the inside of the cup preventing dried SOD build-up and reduces particle formation. Generally, isopropanol is used for the solvent rinse.

5. Materials (delivery lines, cap adapters, and pump equipment, etc) must be compatible with highly polar

organic solvents, esters, alcohols, and ketones. Materials commonly used are PFA, Teflon, and PTFE. A diluted solution of 10% HF must be used to remove particles and residues form silicate based SOD. O-rings should be constructed from Kalrez or PTFE coated viton.

6. Dispensing of the SOD is best accomplished by utilizing a pressurized system. Nitrogen is commonly

used but the solubility of helium in the SOD is less than nitrogen, which means less out gassing from the SOD during application and spin. A precision 0 to 5 psi regulator may be employed for consistent delivery of SOD and uniform pressure. For some SOD applications a Teflon pump has been used with success. Helium is the best pressurizing ambient and is more economical when used directly to pressurized delivery containers stored in containment vessel.

Spin-On Procedure

1. Make certain that the SOD solution to be spun-on is at room temperature. Solution should be permitted

to acclimate to room temperature 24 hours before coating. A cold solution will spin a thinner film, possibly with cloudiness, due to condensation of water vapor from the atmosphere.

2. Set the spinner bowl exhaust for optimal film uniformity and quality (a good starting point is a pressure

differential of 20mm-40mm of water at the chuck). 25mm is a typical setting which may be adjusted for optimal film uniformity.

3. Insure that the spinner bowl is “wet” by running one or two dummy wafers with solvent or by activating

the bowl rinse feature. 4. Films may be applied to the silicon via 2 dispense methods, static or dynamic dispense. For an automatic

SOD coater the typical dispense line diameter and dispense volumes are below:

Diameter of Dispense Line per Wafer Dispense Volume per Wafer

4”/100mm - 0.0625” (1/16) 4”/100mm - 1.0-2.0ml 5”/125mm – 0.0625” or 0.125” (1/16 to 1/8) 5”/125mm – 2.0-3.0ml

6”/150mm – 0.125” (1/8) 6”/150mm – 3.0-4.0ml 8”/200mm – 0.1875” (3/16) 8”/200mm – 5.0-6.0ml

Diameter of the dopant dispense lines are determined so the correct volume of dopant is dispensed in 2 to 3 seconds at less that or equal to 5 psi helium or nitrogen. If a greater pressure than 5 psi is used the rapid dispense may cause splashing or splashback of dopant on the silicon. If the pressure is too low and it takes longer to dispnse the SOD, the resultant coating will be thicker in the center due to excess solvent evaporation. If not enough SOD is dispensed uncoated wafer surfaces will be apparent in addition to particles dispensed on the surface of the slice. Any SOD that may have splashed onto the uncoated (backside) of the wafer can be removed by a backside rinse. The supply lines for the SOD should be as short as possible. Longer lines take more SOD to fill and more solvent flush and are a potential source of particulates. The dispense volume of SOD onto the wafer is varied primarily by varying the dispense time. The time of dispense is the



variable as the pressure is approximately 5 psi and the line for the dispense is correctly determined per wafer diameter. The volume of SOD needed to sufficiently coat the wafer is in the dispense volume chart or may be determined experimentally. Assume an 8” or 200mm wafer needs about 5.5ml of dopant to coat correctly. The flow rate of your dispense line is determined at 5 psi in this case 3/16” line is about 2 ml per second. Therefore a 5.5 ml dispense volume divided by 2ml/second equals about 2.75 second dispense time (5.0 ml/sec equals about 2.5 seconds dispense time). Longer dispense times will cause particle ring spin defects.



SPIN-ON AND CURE OF SOD

A typical dispense schedule is as follows: Stationary Dispense (100mm and smaller wafers) Step 1. Wafer placed on vacuum chuck with cup exhaust on. Step 2. Dopant dispense approximately 3 seconds. Step 3. High Speed Spin. 3000 rpm or desired rpm. 6-10 seconds for optimum coating. High spin speeds can reduce uniformity and increase edge bead.

Dynamic Dispense (125ml and larger wafers) Step 1. Wafer placed on vacuum chuck with cup exhaust on wafer is pinning about 300 rpm. Step 2. Dopant dispense approximately 3 seconds. Spread at 300 rpm for 0.1 to 0.3 seconds. This spread time can produce better coating and improve wafer uniformity. Step 3. High Speed Spin. 3000 rpm or desired rpm. 6-10 seconds for optimum coating. High spin speeds can reduce uniformity and increase edge bead.

Note: If any dopant wraps around onto backside of silicon wafer during spin coating it may be removed by a backside rinse if your spinner is equipped with such a feature. This is accomplished at about 1400 rpm after the high speed spin cycle. Spin speed can be adjusted to remove the SOD desired. Slower spin speeds will permit the backside rinse to wrap around the edge of the silicon slice and remove more of the SOD edge bead. After the backside rinse the wafer is dried at 3000 rpm for 5-10 seconds and then the wafers are cured before diffusion. Film Cure

1. Soft bake the spun films if necessary, (some spin-ons require no baking – just spin and load) at approximately 100˚C for 60 seconds on the hot plate if the spinner is equipped with an on-line bake/cure system, or bake at 100˚C for 15 minutes (air convection oven) for off-line processing.

2. Please contact us if you have any questions.

Note: Use of the new automated closed rotating cup spinners provide a much more uniform coating of the substrate with a reduction in particles on the wafer. Both Semix and Dianippon screen manufacture these machines.

TROUBLE SHOOTING


SPIN-ON DOPANTS (SOD)

DIFFICULTY POTENTIAL CAUSE & POSSIBLE SOLUTION Film Thickness Variation Over Time Inadequate Coat Film Thickness Variation Across Wafer Radial Striations Puddle Mark in the Center of Wafer Edge Bead Cracking of Film Cloudy Film/Bubbles in Film or Chuck Imprint

SOD has exceeded shelf life (gelling) SOD too cold. – Allow the SOD to warm to room temperature for 24 hours prior to use. Variation in room, spinner, wafer and/or SOD temperature. – Check and maintain uniform

ambient and conditions for best results. Change in cup exhaust or laminator flow. Cup exhaust out of adjustment, either too high or too low. – Use the recommended range for

exhaust settings. SOD coating thicker. – SOD spun at slow rpm. Spinner rpm variation. Spinner acceleration rate variation. Change in film cure time or temperature. Spinner cup not rinsed and wet with solution SOD evaporation rate of SOD too rapid. Spinner rpm too low. Dispense volume of SOD too low.

Insufficient volume of SOD. Spin speed too slow. No solvent in spinner cup. Chuck vacuum too high. Chuck fabricated from poor materials. – Use polypropylene Derlin, P.E.E.K. or KEL-F. Chuck too small. The spinner cup exhaust is too high. The increased air flow above the surface of the wafer

causes the solvents in the SOG to evaporate too fast. Usually reducing the exhaust will solve this problem.

Silicon surface must be clean and free of haze or dust. If a silicon test wafer has been stripped too many times a residue may remain on the surface and cause spin striations.

Shelf life of SOD has expired. Expired SOD or SOD not stored properly can gel or have viscosity changes that cause spin problems.

Too much time between dispense and spin. Plastic in dispense system incompatible with polar organic solvents. Laminar flow too high, reduce flow. Wafer too hot, solvents evaporate too fast. Spin speed too slow. SOD has exceeded its shelf life and the viscosity is too high. SOD too thick. Particles or defects on substrate. Use of a chill plate after film cure. Cool down after cure too rapid. Dew point (relative humidity) of spin environment too high. It is advised that the humidity in

the spin cup be controlled between 37% and 43% for best results. Phosphosilicates (especially those with 4% or greater mole percent, P205) require a lower humidity due to the hygroscopic nature of phosphorous doped glass. 25% to 35% humidity is recommended for phosphosilicates. High humidity will cause haze related to condensation.

Too much time between spin and post-spin bake Exhaust misadjusted Leak in pump dispense system Use of gas other than helium in pressure dispense system. Too little time betweend dispense and spin. Wafer too hot.

TROUBLE SHOOTING


Cloudy Film/Bubbles in Film or Chuck Imprint (contd) Pinholes or Other Film Discontinuities Wrap Around Particles In or On Film

Hand dispense of SOD Room spinner cup and wafer too cool. – Increase the cup temperature to at lest 68-72˚F.

Temperature and humidity control chambers that enclose the entire cup assembly are available Allow SOD to ward to room temperature 24 hours before spinning. Haze can form a SOD layer

if it is cold from moisture condition. Cup exhaust too low. – Increase cup exhaust. Poorly cleaned water Spinner cup too small (splash-back). Use of spread cycle to wafer edge. Too large a vacuum of SOD (flooding). Acceleration too slow. SOD bottle repeatedly opened and closed. SOD evaporation on spinner cup, dispense line or dispense tip. Cup exhaust too low. The SOD forms a mist of droplets above the substrate when spinning. If

cup exhaust is too low and mist not pulled down below the plane of the wafer surface particles or bubble like defects may form in the film.

The spinner chuck should be made of Kalrez or polypropylene. Metal chucks can chill the wafer and cause temperature gradients which can cause poor uniformity of spun film. Chucks made of Teflon are too soft and may distort at high rpm.

Mechanical pumps are a potential source of particles. They are difficult to regulate and require maintenance. Helium pressurization is better as it provides fewer particles and the pressurization is easily controlled. Helium is superior to nitrogen as it is less soluble in SOD and will avoid the possibility of bubbles in the film, due to outgassing.

Spin coat test wafers are not fully cleaned before optical particle counts. It is recommended to use prime grade wafers that have not been stripped or used too many times.

Make sure the SOD is at room temperature at least 24 hours before use. Cold SOD can increase your particle defect count.

Spinner cup dirty. Establish a routine schedule where cup is cleaned and that the cup rinse is in good working order. A 10% HF rinse may be necessary to remove dried SOD and particles.

Poor cup rinse or no cup rinse. Deposits formed by evaporation of SOD can flake off and cause particles in spun film, the cup rinse should be checked, the flow of IPA may need to be increased to avoid dried SOD.

Dispense line or dispense tip nozzle is dirty. Dispense line was not flushed properly or the SOD was allowed to dry in the dispense line. This will cause large amounts of particles occurring on test wafers. Several flushes of IPA through the line can solve the problem; if not the supply line must be replaced.

Dried SOD on a dispense tip can also be a source of particles. The dispense tip and dispense line should always be flushed on a regular basis and SOD should not be allowed to remain in dispense lines or dispense tip when spinner is not in use. Dried SOD may require an HF removal.

The dispense line length and diameter should be optimized. The dispense line should be the shortest possible distance from the SOD source to the dispense nozzle. Longer lines are a potential source of particles. The diameter of the dispense line should be optimized for the correct dispense time and flow rate. Larger wafers require a larger line to deliver SOD properly in the same time as a smaller wafer generally about 3 seconds in time.

The IPA flush solvent may not be clean and introduce particles which can give a high particle count. Use a new flush bottle with new IPA, then check for particles again.

Air may get into the SOD dispense tip and cause the SOD to dry which may be a potential source of particles. Adjust or repair the suck back to function properly so that no air gets into the dispense tip.

The SOD bottle should not be left for more than 5 hours in a coater as the SOD may dry on the interior of the bottle and cause particles. If you are coating a small number of wafers use d 125 ml bottle of SOD source, not a large bottle. Optimize the SOD bottle size for your coating applications so you always have fresh SOD.

Use of a filter between the SOB bottle and dispense nozzle is not advised. Filters can become a source of particles as they can clog or trap bubbles.

A low exhaust can cause a high particle count. Increase the exhaust so that it will suit the spin coater properly.

PRODUCT DESCRIPTION


ALUMINUM FILM Al-100 ALUMINUM BORON FILM AlB-120

ALUMINUM FILM Al-111 Aluminum diffusions in silicon present the advantage of providing junctions that can withstand very high voltages. Aluminum diffusion is widely employed in the power semiconductor industry. The diffusion coefficient of aluminum in silicon is three times higher that that of Gallium and five times higher than that of Boron. Aluminum also fits into the silicon lattice better than any other “P” type dopant. Aluminum 1%, Aluminum Film (100) and Aluminum Film + Boron (120) are Non SiO2 solutions; they are metal organic solutions from which Aluminum may be diffused into silicon. These solutions should be applied to lapped or as-cut silicon for best results. Application of the dopants to the silicon involves placing several drops of solution in the center of the silicon wafer and spinning the wafer on a vacuum chuck for 10-15 seconds at a speed at approximately 2000 rpm to provide a uniform coating. After spinning, wafers may be further dried at a temperature of 100˚C to evaporate any additional solution. A hot plate may be used. Wafers may be stacked with coated sides facing each other and diffusion conducted in a nitrogen or argon ambient. Diffusion parameters are outline by the two graphs. Figure A represents an aluminum diffusion conducted for four hours at a temperature of 1275˚C in Argon + 10% hydrogen with a sheet resistivity of approximately 80 ohm/square. 100% Argon has also been used with good success. Figure B delineates a simultaneous diffusion profile of boron and aluminum diffused at a temperature of 1260˚C for 17 hours. Both aluminum film and aluminum film with boron may be thinned with ethoxyethonal if needed. Also, the concentration of boron present in the simultaneous diffusant may be varied upon request to yield the desired concentration or sheet resistivity. Wafers may be cleaned in HF after diffusion to remove any glasses. Uniformity and consistent diffusion is sometimes difficult to control with aluminum spin-on due to oxidation. There fore, it is important to remove all oxygen from the diffusion ambient.

PRODUCT DESCRIPTION


DIFFUSION RESULTS DATA Al-100 – AlB120

Figure A ----- Figure B Spin-on Aluminum Al-100 4 hours at 1275˚C in Argon Spin Speed 3000 rpm Sheet Rho- 80 ohm/square

Spin-on Boron and Aluminum AlB120 Simultaneous Diffusion 1250˚C 17 hours Spin Speed 2000 rpm Diffusion Gas: First 2 hours in 10% Hydrogen 90% Nitrogen or Argon, 100% Argon may also be used Balance of 15 hours in 100% Argon 20% Oxygen may be introduced at tail of diffusion to reduce boron stain

PRODUCT DESCRIPTION


PRODUCT DESCRIPTION


ALUMINUM FILM Al-110 ALUMINUM – BORON FILM AlB-120A

Aluminum Film (110) and Aluminum – Boron Film (120A) are Sio2 based formulations for the diffusion of Aluminum or Aluminum and Boron into silicon. Both solutions are applied to wafers which have oxide free surfaces. This may be achieved by soaking the wafer in H2O2 + H2SO4 (1 to 4) by volume at 80˚C for 5-10 minutes, followed by a Dl water rinse and HF soak. The wafers are then cleaned in Dl H2O followed by an Isopropanol rinse and spun dry. Dopant may be applied to silicon via spinning on a “Derlin” polymer chuck upon which the wafer is positioned. Several drops of the solution are placed in the center of the wafer. After a few seconds the solution will wet out over the surface and the wafer is then spun at 3000 rpm for 10-15 seconds until an “oxide” looking film is formed. The wafer are then removed from the spinner and dried on a hot plate or other suitable heat source at a temperature of 150˚C for 10-15 minutes. The amount of Aluminum diffused is sensitive to the ambient use during diffusion. Any oxygen will reduce the surface concentration and in large amounts will prevent any Aluminum from diffusion. The optimum diffusion ambient is Nitrogen or Argon with a small amount of hydrogen or carbon monoxide. 100% Argon may be used successfully. During diffusion, wafers may be coinstacked with coated sides facing each other. You obtain a much lower surface concentration with wafers stacked vertically and not in contact with others. These solutions work best on a lapped wafer surface, or as-cut as the surface area of the silicon is greater than a polished slice. Aluminum converts to the oxide or leaves the film during the first 1 to 1-1/2 hours. Therefore, it is a limited source and the surface concentration will decrease with the square root of the time of diffusion for longer diffusion. When longer diffusion times are employed, some silicon nitrade formation may occur. There fore, it may be advisable after the first two hours of diffusion to change the ambient and add a few percent oxygen to prevent any stains from forming. This is especially advantageous for Al-B film to prevent Boron stains. Advise 80%, N2; 20%, O2. Also reverse side of wafer may be coated with SiO2 film to prevent any diffusion or damage. Junction fabrication with Aluminum will have sharp reverse breakdowns and low leakage current. Typical uses are P-Guard Ring, Transistor, and Rectifier. Wafers may be cleaned in 48% HF after diffusion to yield a clean, defect free surface. Uniformity and consistent diffusion is sometimes difficult to control with aluminum spin-on due to oxidation. Therefore, it is important to remove all oxygen form the diffusion ambient. Some empirical work may be necessary to determine the best process for your device.

PRODUCT DESCRIPTION


ALUMINUM DIFFUSION DATA

Silicon: N(111) lapped 25-50 Ohm-cm; N(100) 10 Ohm-cm Diffusion: Temperature: 1250˚C Spin Speed 3000 rpm Abmient: Argon with 5% H2 Diffusion Time: 2 hours Solution Sheet Resistivity Concentration Al 110 N100 – 70 ohm/square

N111 – 100 ohm/square Al 110 – 2%

Al 111 N100 – 90 ohm/square N100 – 120 ohm/square

Al 111 – 1%

AlB 120A N111 – 3 ohm/square AlB 120A – Al 2% B 5% AlB 121A N111 – 6 ohm/square AlB 121A – Al 1% B 4% Aluminum Diffusion Al 110 Aluminum Boron Diffusion AlB 120A --------- 2 hours at 1250˚C Gas 80% Ar 20% H2 Junction depth 1 mil, sheet rho 90 ohm/square Silicon lapped (111)

16 hours at 1250˚C Gas 80% AR 20% H2 Sheet rho 0.8 ohm/square Silicon lapped N (111)

PRODUCT DESCRIPTION


ALUMINUM GALLIUM FILM AlGa – 130

Aluminum Gallium Film 130 is a formulation with organic solvents from which Aluminum and Gallium may be diffused simultaneously into silicon. The solutions should be applied to wafers which have an oxide free surface. This may be accomplished by soaking the wafer in 80˚C H2SO4 + H2O2, 4 to 1 by volume for 5-10 minutes. Wafers may then be rinsed in Dl H2O, followed by a 48% HF dip with Dl H2O rinses, ispopropanol rinse and spun dry. The Aluminum Gallium (130) should be applied to an as-cut or lapped surface for best results. The dopant solution is applied to the silicon wafer via the use of a (Derlin) polymer chuck upon which the wafer is positioned. Several drops of the solution are permitted to spread out over the wafer surface. The wafer is then spun at approximately 3000rpm for 10-15 seconds until an oxide looking film is formed. The wafers are then removed from the spinner and dried on a hot plate or other suitable heat source at a temperature of 150˚C for 10-15 minutes. The amount of dopant that diffuses into the substrate is sensitive to the ambient used during diffusion. Any oxygen will reduce the surface concentration and in large amounts will prevent any Gallium or Aluminum from diffusing. The optimum ambient is Nitrogen or Argon with a small amount of hydrogen or carbon monoxide. Near the end of the diffusion cycle or after the first 2 hours of diffusion it may be advantageous to induce a small amount of oxygen into the ambient in lieu of hydrogen to prevent excess silicon nitride formation. Post diffusion clean up is accomplished through the use of a 48% HF soak followed by appropriate Dl H2O rinses. During diffusion wafers may be cionstacked with coated sides facing each other. You obtain a much lower surface concentration with wafers stacked vertically and not in contact with each other. Diffusion Data: Conditions: Wafers diffused face to face, 100% Argon may be used. Time: 2 hours Temperature: 1250˚C Ambient: 90%-N2 + 10%-H2 1.75 hours Last 15 minutes 90%-N2 + 10%-O2 Silicon Use: N(111) lapped 25-50 ohm-cm N(100) polished 10-30 ohm-cm Solution Silicon Sheet Resistivity Solution

Concentration Al Ga 130 N100

N111 17 ohm/square 20 ohm/square

2% Al – 3% Ga

Other concentrations available upon request.

PRODUCT DESCRIPTION


GALLIUM FILM GA-250 GALLIUM BORON FILM GAB-260

Gallium film is applied to wafers that have a clean oxide free surface. This may be achieved by soaking the wafer in H2O2 + H2SO4 at 80˚C for 5-10 minutes. Wafers are then soaked in HF to remove oxide and a Dl water rinse is employed followed by an isopropanol rinse and spin dry. Gallium film with boron is a spin-on solution designed to diffuse boron and gallium simultaneously. Due to the difference in diffusion coefficient of gallium and boron. (Gallium diffuses three times faster than boron) it is possible to create graded P type junctions that can withstand high voltages. Gallium-boron film may then be spun on the silicon wafer at a speed of 500 to 2000 rpm or painted on the surface of the silicon wafer. Another method may be conducted by placing several drops of the solution in the center of the wafer and allowing them to spread and cover the entire wafer surface to provide a thick coating. The coated surfaces may then be heat treated at a temperature of 100˚C to 150˚C for 10-15 minutes in air or nitrogen. The surface concentration is sensitive to the ambient used during diffusion. Any oxygen will reduce the surface concentration, and in large amounts will prevent any Gallium from diffusing. The optimum diffusion ambient is Argon with a small amount of hydrogen or carbon monoxide. During diffusion, the wafers may be coinstacked with coated sides facing each other. You obtain a much lower surface concentration than what would be obtained with the wafers stacked vertically and not in contact with each other. Gallium leaves the film by evaporation during the first hour of diffusion. Therefore, it is a limited source and the surface concentration will decrease with the square root of the time of diffusion for longer diffusions. When longer diffusion times are employed in nitrogen, some silicon nitride formation may occur. Therefore, it may be advisable after the first two hours of diffusion to change the ambient and add 10% oxygen to prevent any stains or nitride from forming, or use an Argon ambient. Junctions fabricated with Gallium will have sharp reverse breakdowns and low leakage current. Wafers diffused will exhibit uniform sheet resistivities and junction depths. Wafers may be cleaned in 48% HF after diffusion to yield a clean defect-free surface. Coinstacked wafers may be cleaned in 48% HF followed by a thermal oxide clean up or an acid etch 511 for 5 seconds to yield a clean surface from metallization. Boron staining may be reduced by introducing 50% oxygen into the diffusion ambient during the last few hours of a diffusion. Some empirical work may be necessary to determine the best process for your device.

PRODUCT DESCRIPTION


GALLIUM DIFFUSION DATA

PRODUCT DESCRIPTION


GALLIUM DIFFUSION DATA Diffusion Results: Silicon-N (111) Lapped, 25-50 ohm-cm, Dopant – Ga250

Ambient Temperature Time Wafer Position

Rs ohm/sq Xj microns

90% Ar + CO 1200˚C 70 Minutes Vertical Slots 325 6 90% Ar + CO 1200˚C 70 Minutes Coinstack 25 6 90% Ar + CO 1250˚C 70 Minutes Vertical Slots 290 8 90% Ar + CO 1250˚C 70 Minutes Coinstack 14 8 90% Ar + H2 1258˚C 4 Hours Coinstack 13 20

Diffusion Results: Dopant – Ga250 Silicon: N111, lapped, 25-50 ohm-cm, Time 2 hours N110, polished, 10 ohm-cm, Temperature 1250˚C Wafers diffused with coated sides facing each other in a slotted Boat. Ambient: Ar + 10% H2 or 100% Ar

Solution Silicon Sheet Resistivity Ga Concentration of Solution (w/v)

Ga 250 N110 20 ohm/square 2% Ga 250 N111 25 ohm/square 2%

Solution Time Gas Temperature Junction

Depth Sheet Resistivity

B 202 12 hours N2 or Ar 1250˚C 20.0 micron 0.65 ohm/square Ga 250 14 hours N2 or Ar 1250˚C 31.0 micron 13.00 ohm/square GaB 260 14 hours N2 or Ar 1250˚C 40.0 micron 1.80 ohm/square Ga 250 14 hours N2 or Ar 1250˚C 36.0 micron 12.00 ohm/square GaB 260 14 hours N2 or Ar 1250˚C 43.0 micron 0.80 ohm/square B 202 14 hours N2 or Ar 1250˚C 23.0 micron 0.55 ohm/square

Solution % Ga % B

GaB 260 4% 4% Ga 250 2% 0% B 202 5% 5%

Other concentrations of solutions available on request.

PRODUCT DESCRIPTION


ARSENIC as 350-354 AND ANTIMONY Sb 300-303

Arsenic and Antimony spin-on dopants are formulations designed to yield “N” type junctions in silicon with minimum surface (rosette) damage. Some typical applications are I.C. buried layer, MOS and some solar applications. ADVANTAGES Consistent results and minimal surface damage to substrate. Economical equipment costs when compared to ion implantation or CVD requirements. Higher purity, no particulates, long shelf life, and superior homogeneity. Good control of doping with low diffusion coefficient of Arsenic and less out diffusion with Anitmony in subsequent

processing due to its atomic size. This permits lower resistivity GP layers as well as thinner layer fabrication. Antimony and Arsenic solutions are clear solutions with the following properties: Solvent: Alcohol Flashpoint: 14˚F Filtration: 0.1 micron Shelf Life: Greater than 3 months at 40˚F Impurities: Less than 0.04 ppm (Fe, Cr, Ni, K, Na) % Dopant Compound %SiO2 Potential

Applications Sb 300 3.20 3.10 I.C. Sb 301 3.20 2.20 I.C.Sb 302 3.50 2.20 I.C.Sb 303 4.10 2.10 I.C.

As 350 0.50 2.10 Resistor As 351 0.70 2.50 Buried layer As 352 1.00 3.30 Buried layer As 353 1.54 5.00 MOS As 354 2.00 4.20 MOS

Notes: The viscosity of these solutions changes slightly over a period of time. A greater change is observed if the solution is stored at an elevated temperature. The best temperature for storage is 0-5˚C where the maximum change in viscosity is less than 0.5 cps. The solution must warm to room temperature for 24 hours before spinning for consistent results. It is important to maintain good process technique to achieve good results consistently and avoid damage to the substrate. Temperature, 68˚F to 73˚F and humidity 32 to 38% along with a programmed dispense give best results.

PRODUCT DESCRIPTION


ANITMONY & ARSENIC DIFFUSION (1) The silicon used should be dislocation free; less than 400 defects per square centimeter. Faults in the substrate may cause rosettes in future processing. The silicon should be cleaned prior to oxide growth and prior to diffusion with low particle chemicals. The RCA cleaning process (RCA review # 31, June 1970, 187) is recommended, but the common H2O2 – sulfuric acid clean is also good. Both cleaning steps should be followed by a 10% HF dip with Dl H2O rinses and spun dry prior to further processing. Any contact with dust, dirt, or contaminants throughout processing may cause rosettes. (2) Furnace tubes should be purged periodically with dry oxygen bubbled through trichloroethylene, trichlorethane, or use of a 5% HCl/95% oxygen mixture will suffice. This cleaning process done at a temperature 10-20˚C higher than the diffusion temperature will remove metal contaminants as their volatile halides. (3) Rosette formation may be linked to devitrification of Arsenic or Antimony spin-on glass and field oxide. In light of this concept, elimination of stacking faults in the oxide growth should reduce the formation of rosette. Methods for reduction of defects are as follows: Method A: Stacking faults may be gettered with a Chlorinated Oxidation using HCl gas or trichlorethane. -Ramp from 925˚C to 1100˚C in dry O2 -Oxide at 100˚C for 6 hours in 2% HCl/98% dry O2 -Ramp down to 925˚C in dry O2 Method B: Use of a “sacrificial oxidation” is recommended; this is a preferred method and is as follows: -Ramp from 900˚C to 1125˚C in dry oxygen -Oxidize at 1125˚C for 1 hour in steam -Ramp down to 900˚C in dry oxygen -Remove oxide with HF -Grow oxide again using above technique -Oxide may now be patterned for diffusion Method B yields a very low defect oxide of about 6000 angstroms. When arsenic or antimony spin-on diffusion is done on this oxide, a very low rosette density results, but the oxide may also reduce the diffused dopant concentration. APPLICATION OF THE SPIN-ON SOLUTION The wafers should be clean as mentioned before. It is advantageous to heat the clean silicon at 200˚C to 400˚C to remove any residual moisture that may be on the silicon surface. After this bake, the solution should be spun on the wafers within 30 minutes in an environment that is always constant. An ideal environment would be 23˚C at 30% relative humidity. Keeping the spin-on ambient constant, as well as the temperature of the solution being applied, provides consistent results. When spinning, accelerate spinner as fast as possible to desired rpm. Decelerate at a maximum rate. Spin speed is usually 3000rpm for 15 seconds.

PRODUCT DESCRIPTION


ANTIMONY & ARSENIC DIFFUSION

WAFER DIAMETER APPROXIMATE AMOUNT OF DOPANT SOLUTION NEEDED

2” 0.75 cc 3” 1.00 cc 4” 1.50 cc 5” 2.00 cc 6” 3.00 cc

Exhaust on any automatic coater is extremely critical. If any kind of spin thickness or uniformity problems are noticed, exhaust normally is set too high. Heat Treatment – The films after spinning are hygroscopic. It is best to heat the films in an oven or on a hot plate at 150˚C for at least 15 minutes in air to eliminate this problem. After heat treatment, the film is no longer sensitive to humidity. Rosettes - A common problem of rosettes, hexagonal crystallized (phases) regions within the field oxide regions, can be substantially minimized (thus reducing substrate damage) through cleanliness, low oxygen during diffusion, low temperature, and short times of diffusion. Size of rosette is a function of long diffusions, while density is a function of oxygen content. The higher the oxygen content, the higher the density of rosettes. Surface damage is also minimized by the use of thinner spin-on oxide films. A solution diluted with ethanol yields a thinner oxide and minimal surface damage with a slight increase in sheet resistivity. Whenever possible, insofar as electrical parameters are not affected, higher spin speeds or dilutions of the dopant (ethanol is recommended as a diluent as long as ethanol is electronic grade with a 0.2 micron filtration) may be used to make a thinner coating and reduce the chance of rosette formation. To prevent silicon damage, the following limits on the oxygen content at a given temperature, should not be exceeded for arsenic diffusion:

Temperature Percent Oxygen 1000˚C ≤25% 1100˚C ≤20% 1200˚C ≤10% 1250˚C ≤5%

Diffusion – The appropriate times and temperature of antimony and arsenic diffusion will depend on customer needs, as well as the concentration and junction depth needed. Diffusion Results – The following data is only a starting point to achieve desired results. Different types of furnaces ramp at different rates, sometimes results will vary. If this occurs, adjust time and temperature. If much lower sheets are desired, you may have to raise temperature. If help is required on achieving a particular spec, please contact us.

PRODUCT DESCRIPTION


ANTIMONY DIFFUSION DATA FOR Sb-300 – Sb-303

One Hour Diffusions, Sheet Resistance, Ω/ Diffusion

Temperature, ˚C Product %O2 in Tube Ambient

3% 5% Junction Depth,

Microns 1150 Sb-300 110 112

Sb-301 107 111 Sb-302 106 107 0.8 Sb-303 103 5

1200 Sb-300 58 60 Sb-301 50 53 Sb-302 47 48 1.3 to 1.5 Sb-303 46 47

1225 Sb-300 39 40 Sb-301 30 32 Sb-302 27 28 1.6 to 2.0 Sb-303 25 26

1250 Sb-300 29 30 Sb-301 23 24 Sb-302 22 23 2.7 to 2.9 Sb-303 21 22

1275 Sb-300 23 24 Sb-301 18 19 Sb-302 16 17 4.8 to 5.3 Sb-303 13 14

Temperature,

˚C Time Ambient RS, Ω/ Sj, Microns

Antimony Sb-300 1250 1 hr 5% O2 27 2.5

1250 3 hr 4% O2 21 4.2 1250 10 hr 3% O2 17 8.2 1250 19 hr 7% O2 20 7.0

Antimony Sb-303 1225 60 min 65% O2 24 2.3

1250 30 min 50% O2 19 2.1 1250 60 min 10% O2 21 2.7 1250 120 min 4% O2 16 4.4 1265 75 min 5% O2 18 3.7 1275 20 min 60% O2 17 2.4 1275 70 min 5% O2 15 4.5

PRODUCT DESCRIPTION


ANTIMONY BURIED LAYER PROCESS

Spin-On -Sb-302 Silicon Type – P Orientation – 111 Polished Process - Sb Buried Layer Spin Speed - 3000 rpm Size – 4” Resistivity – 10-20 ohm-cm Spin Time - 15 seconds Prebake - 15 minutes at 150˚C Step 1 Step 2 Step 3 Furnace Temp. - 800˚C 1225˚C 800˚C Temp. Cycle -Auto Ramp Up 3 hours Auto Ramp Down Gas Flow N2 -4 1/m 4 1/m 4 1/m O2 -150 cc/min 150 cc/min 40 cc/min

Remark: Wafers cleaned in HF and given 1 hour drive in O2 and 1 hour in N2 yield the same sheet resistivity but deeper junction with no surface damage. Sheet Resistivity Ω/

Spin-On - Sb-303; Sb 304 Silicon Type – P Orientation – 111 Polished Process - Sb Buried Layer Spin Speed - 2000 rpm Size – 4” Resistivity – 10-20 ohm-cm Spin Time - 15 seconds Prebake - 15 minutes at 150˚C Step 1 Step 2 Step 3 Furnace Temp. - 800˚C 1225˚C 800˚C Temp. Cycle -Auto Ramp Up 1 hours Auto Ramp Down Gas Flow N2 -4 1/m 4 1/m 4 1/m O2 -400 cc/min 400 cc/min 40 cc/min

Sheet Resistivity Ω/ Note: Other improved antimony solutions are available for specific applications. Please contact us.

PRODUCT DESCRIPTION


ARSENIC DIFFUSION DATA Sheet Resistance, (Ω/) Junction Depth-Microns

Spin Speed 3000 rpm Silicon P type Polished

Temp: 1000˚C Gas: 75% N2 – 25% O2

15 30 45 60 As-350 120 95 77 65 As-351 111 75 62 53 As-352 100 64 53 46 As-353 96 61 48 41 As-354 94 59 46 38 Xj Microns 0.18 0.21 0.24 0.25 Temp: 1050˚C Gas: 75% N2 – 25% O2



15 30 45 60 90 240 As-350 50 35 30 22 20 18 As-351 45 29 22 18 15 13 As-352 41.2 24 18 14 12 10 As-353 42 24 17 14 11 9 As-354 43 23 17 14 11 8 Xj Microns 0.40 0.80 1.10 0.50 1.98 3.30

PRODUCT DESCRIPTION


ARSENIC DIFFUSION DATA Sheet Resistance, (Ω/) Junction Depth-Microns

Spin Speed 3000 rpm Silicon P type Polished

Temp: 1200˚C Gas: 10% O2 – 90%N2

Time Minutes 15 30 45 60 90 240 Solution As-350 35.0 31.0 20.0 17.0 14.0 14.0 As-351 30.0 25.0 15.0 13.0 12.0 11.0 As-352 28.0 16.0 13.0 10.6 10.4 8.9 As-353 27.0 16.0 12.0 10.0 8.2 7.0 As-354 28.0 16.0 12.0 10.0 7.8 6.7 Xj Microns 0.80 1.20 1.54 1.82 2.34 3.70 Temp: Gas:

Time Minutes 15 30 45 60 90 240 Solution As-350 30.0 25.0 15.0 13.0 12.0 11.0 As-351 26.0 18.0 12.0 11.0 10.1 8.0 As-352 24.0 13.0 9.8 9.1 8.2 7.1 As-353 23.0 13.0 10.0 8.2 7.1 6.1 As-354 22.5 14.1 10.4 8.5 6.6 5.4 Xj Microns 1.37 2.00 2.43 3.20 3.80 6.50 Arsenic Typical Process for MOS

Spin-On - Process - Spin Speed - Spin Time - Prebake - Step 1 Step 2 Step 3 Furnace Temp. - 800˚C 1225˚C 800˚C Temp. Cycle -Auto Ramp Up 1 hours Auto Ramp Down Gas Flow -4 I.p.m. N2 4 I.p.m. N2 4 I.p.m. N2 -800 cc/min O2 800 cc/min O2 800 cc/min O2

Sheet Resistivity – 27 ohm per square

PRODUCT DESCRIPTION


ARSENIC DIFFUSION DATA Variation of Sheet Resistance (Ω/) with Oxygen Concentration

Spin Speed 3000 rpm. Silicon P type Polished

Units ohm/square

Time Minutes 60 90 120 170 Oxygen Content 10% 108.2 85.6 70.1 53.8 20% 66.7 51.1 45.2 41.2 30% 68.4 52.0 48.1 41.2 50% 80.1 72.1 85.2 78.5 Junction Depth (Microns) 0.18 0.22 0.26 0.32

Arsenic Diffusions Variations with Oxygen Spin Speed 3000 rpm

Units ohm/square

60 minutes 5% O2 95% N2

Temperature 1100˚C 1150˚C 1200˚C Solution As-350 32.1 23.5 20.1 As-354 30.2 21.0 13.5 Sj Microns 0.6 1.1 2.1

60 minutes 10% O2 90% N2

Temperature 1100˚C 1150˚C 1200˚C Solution As-350 38.2 27.1 19.9 As-354 20.2 13.1 9.9 Sj Microns 0.6 1.1 2.0

PRODUCT DESCRIPTION


BORON FILM B-200 TO B-202 PHOSPHOROUS FILM P-450 TO P-452

B 200-202 and P 450-452 are solutions of boron and phosphorous from which it is possible to diffuse boron and phosphorous in a one step simultaneous diffusion to produce a rectifier, or in a single step diffusion for creation of a “P” or “N” type junction in silicon wafers. Application of dopant involves the following steps:

1. Wafers should be clean to remove all traces of grease or cutting oils. Wafers should then be soaked in hot H2SO4 – H2O – 4-1 by volume then Dl H2O rinse and soak in 48% HF to remove any metallic impurities or glasses which may inhibit the diffusion process. Wafers are then rinsed with appropriate Dl H2O rinses and spun dry for application of dopant.

2. Dopant is applied by spinning, painting, or spraying. The preferred method is by spinning. Several

drops of solution are placed in the center of the wafer then spun at 1000-5000 rpm for 10-15 seconds. Slower spin speeds yield a thicker film. The wafer is then removed from the vacuum chuck and baked at 100˚C to 200˚C for 10-15 minutes to harden the film. If there is difficulty with dopant flowing over the surface of the wafer, it may be necessary to produce a hydrophilic surface. This may be accomplished by soaking the wafer in 80˚C H2SO4 – H2O solution for 15 minutes. The wafers are then rinsed and dried for application of dopant.

3. For simultaneous diffusions such as a rectifier, the boron dopant is applied first. Then the wafers with

boron coated one side (optional) may be heated to 200˚C to form a hardened film. The boron coated wafers may also be heated to 475˚C for a short time to form a smooth glassy surface of B2O3, infra-red is also suitable. The phosphorous dopant is then supn on and dried at 150˚C-200˚C. To avoid dopant crossover, it is advantageous to pair the following boron and phosphorous dopants: P450, P451, P452 with B200, B200B, B201, or B202 to achieve desired concentrations.

4. Diffusion may be conducted from 900˚C to 1300˚C in an atmosphere of 75% nitrogen, 25% oxygen.

For simultaneous diffusion, boron coated sides should face boron coated sides and phosphorous should be placed against phosphorous coated sides. To aid post diffusion separation of wafers, fine high purity aluminum oxide may be sprinkled between the coated faces. The wafers may then be coinstacked for diffusion. Our Aluminum Oxide Type A may be used, or a neutral diffusion perform (See our Diffusion Preform Catalogue).

5. Post diffusion cleanup is accomplished through the use of a 48% HF soak after which wafers are

separated and rinsed. If there are any boron stains present after diffusion, it may be necessary to incorporate more oxygen into the ambient during diffusion or a 511 etch for 5 seconds will remove any stains and render a suitable surface for subsequent metallization. Post diffusion wafers may be placed in a boat and a steam clean or thermal oxide growth can be used. Steam is injected into the diffusion tube employing oxygen as a carrier gas at 1000˚C for 30 minutes. Wafers are deglazed with subsequent HF soak to remove oxide. This is an excellent cleaning method.

PRODUCT DESCRIPTION


BORON FILM B-200 TI B-202 PHOSPHOROUS FILM P-450 TO P-452

SOLUTION CONCENTRATION OF SOLUTION (W/V)

% DOPANT COMPOUND

POTENTIAL APPLICATION

B200 8.0 Rectifier SCR B200B 7.0 Rectifier SCRB201 6.0 Rectifier SCRB202 5.0 Rectifier SCR

P450 33 Rectifier SCRP451 27 Rectifier SCRP452 15 Rectifier SCR

Diffusion Results – N111 lapped silicon 10-25 ohm/cm Wafers stacked face to face 14 hours 1250˚C B200 - .012 ohm/square P450 – 0.15 ohm/square B200B - 0.20 ohm/square P451 – 0.20 ohm/square B201 - 0.20 ohm/square P452 – 0.35 ohm/square B202 - 0.80 ohm/square Note: After diffusion and HF clean, the separated wafers may be placed in a slotted boat for a steam oxidation. 30 minutes at 950˚C will suffice, with ramp up and down. This oxidation leaves the wafers clean and removing all stains. Wafers are then cleaned in HF and are ready for subsequent processing. Typical Impurity Analysis (PPM)

Fe 0.05 Na 0.01 An 0.08 Ag 0.05 Mg 0.05 Au 0.05 K 0.09 Ca 0.01 B 0.01 Cu 0.01

Storage, Handling and Safety Precautions to be taken should include those used in handling common organic solvents: Use in well ventilated areas and avoid inhalation of the vapors as well as eye or skin contact. The recommended temperature for long term storage is 0˚C to 4˚C. See the Product Safety Data Sheet for detailed information.

PRODUCT DESCRIPTION


PHOSPORHOUS FILM P-500 TO P-509 BORON FILM B-150 TO B-155

B-150-155 and P500-509 yield doped layers on the silicon substrate upon drying. Advantages are improved yields, high purity, consistent coating, no problems with boron or phosphorous source wafers sticking to boats and no storage of source wafers. These solutions are high purity solutions from which boron and phosphorous may be diffused into silicon with little or no surface damage. These solutions have a shelf life of greater than 3 months at room temperature, longer times with refrigerated storage between 32˚F and 40˚F. The boron SODs may also be used as an etch stop. The surface concentrations observed upon post diffusion are a function of the concentration of dopant in SiO2 film. The following concentrations are available: % Dopant Compound %SiO2 % Dopant

Compound %SiO2

B150* 0.40 5.0 P500 0.06 8.0 B151* 1.00 5.0 P501 0.20 8.0B152* 1.50 5.0 P502 0.24 8.0B153* 2.00 5.0 P503 0.30 8.0B154* 3.80 0.0 P504 0.50 8.0B155* 4.00 0.0 P505 1.00 6.0 P506 3.00 6.0 P507 4.00 4.0 P508 8.00 5.0 P509 10.50 5.0 * Boron solutions B150 through B155 are unaffected by low humidity during application and subsequent processing

Application of dopant to silicon involves spinning at 2000 to 6000 rpm to produce an oxide looking film. Dopant would wet out uniformly over the surface of the silicon. If not, it will be necessary to produce a suitable hydrophilic surface for dopant to wet. This is accomplished by soaking the wafer in NH4OH/H2O2 or H2SO4 – H2O2 solutions with rinses to render a suitable surface. After dopants are spun on, the wafer is heated to 200˚C for 10-15 minutes to harden the film. These solutions contain ethyl alocohol as a solvent and may be thinned with ethanol or isopropanol to modify concentrations. These solutions of boron and phosphorous should be applied using a polypropylene or delrin chuck for spinning. Approximately 1.0 ml or less is needed for a 2 inch slice or about 2.0 ml fir a 4 inch slice. After prebake, wafers may then be placed into the diffusion boat. A quartz “V” boat or oxidation boat with 0.1 inch spacing works well. Wafers should be placed perpendicular to the gas flow of the diffusion tube with 3 to 5 coated dummy slices at each end of the boat. Deviation in sheet resistance is reduced by placing coated sides facing each other. Diffusion may be conducted from 900˚C to 1300˚C depending on process specifications in 90%N2, 10% O2 or other suitable ambient. Wafers are cleaned in HF after diffusion.

PRODUCT DESCRIPTION


PHOSPOROUS FILM DIFFUSION DATA Diffusion Results

Spin Speed 5000 rpm Silicon Polished P Type 111 10-20 ohm-cm

30 Minutes 2.5 Hours 60 Minutes 90 Minutes

1100˚C 1100˚C 1220˚C 1235˚C 25% O2, 75% N2 25% O2, 75% N2 25% O2, 75% N2 25% O2, 75% N2

Solution Sheet Resistance ohm/square

Sheet Resistance ohm/square



P450* 0.08 P451* 0.09 P452* 1.00 P509 3.6 2.1 2.8 2.1 P508 4.8 2.2 3.7 3.0 P507 5.8 3.5 5.0 4.0 P506 7.6 3.9 13.0 5.1 P505 20.4 7.5 16.0 7.5 P504 39.2 11.6 40.0 10.6 P503 92.1 25.3 46.0 14.6 P502 182.0 38.5 71.0 17.0 P501 310.0 42.7 91.0 18.0 P500 735.0 47.8 130.0 24.0 * Some surface damage will occur with P450-452 due to concentration. No damage occurs with P500-P509. Note: Slightly lower sheet resistivities can be obtained with more oxygen in the diffusion gas.

Typical Chemical Analysis Na <0.05ppm Ni <0.05ppmK <0.05ppm Mn <0.05ppmFe <0.05ppm Cr <0.05ppm

PRODUCT DESCRIPTION


BORON FILM DIFFUSION DATA Diffusion Results

Spin Speed 5000 rpm Silicon Polished N Type, 10 ohm-cm

Xj in microns

60 Minutes 60 Minutes 60 Minutes 60 Minutes 14 Hours 1000˚C 1100˚C 1200˚C 1250˚C 1252˚C

25% O2, 75% N2 25% O2, 75% N2 25% O2, 75% N2 25% O2, 75% N2 25% O2, 75% N2

Solution






B200* 14.0 4.0 1.0 0.6 0.3 B200B* 12.6 5.0 1.1 0.8 0.7 B201* 15.5 5.0 1.2 0.9 0.8 B202* 46.0 12.0 3.2 2.5 2.0 Xj Xj Xj Xj

B155 22.0 1.0 14.0 3.0 4.0 7.0 2.5 10.0 2.0 B154 68.0 1.0 36.0 2.5 6.0 6.5 4.0 9.0 2.5 B153 188 0.9 65.0 2.4 30.0 6.5 20.0 8.5 12.0 B152 ----- 250 50.0 35.0 22.0 B151 ----- 600 135 58.0 37.0 B150 ----- ----- 393 110 100

* Some staining and damage occurs with B200 through B202. No surface damage with solutions B150-B155. More oxygen will reduce staining. Note: Diffusion in a higher percentage of nitrogen yields lower sheet resistance for boron diffusions.

Typical Chemical Analysis Na <0.05ppm Ni <0.05ppmK <0.05ppm Mn <0.05ppmFe <0.05ppm Cr <0.05ppm

PRODUCT DESCRIPTION


SILICATE SiO2 700 SERIES SPIN-ON GLASSES

Filmtronics’ SiO2 film is a solution of glass forming compound. When applied to a surface such as a silicon wafer, it dries to yield a pure film of SiO2. The glass solutions may be applied to a clean, dry substrate and spun at 1500-6000 rpm to form a thin glass layer which is cured at 200˚C - 900˚C to densify the resultant silicon dioxide film. The cured films are highly amorphous, crack-free and have a very low density of pinholes and particulates. SiO2 solution is an alcohol based solution filtered through 0.1 micron filters. Thickness may be varied with spin speed or diution with ispopropanol or ethanol. A shelf life of more than 3 months is possible at 4˚C (40˚F). Metallic impurities are well below 0.05 ppm. After film is spun-on and cured at 400˚C for one hour, it has a density of 2.1 g/cc, a refactive index of 1.43 and thickness variation of 1% with no striations or pinholes. This undoped oxide film may be used for a diffusion mask in semiconductor processing which is capable of being patterned by standard photolithographic techniques. The solution is also useful in solar cell production and planarization of integrated circuits as an interlevel dielectric. SiO2 700 is suitable for those applications in microelectronics processing where the film thickness is between 1000Å to 3000 Å. If a thickness greater than 3000 Å is needed, several applications of SiO2 700 may be utilized with a cure of 10 minutes at 200˚C or 5 minutes at 400˚C between successive spin-ons. The maximum thickness of these films should be limited to 7000 Å to avoid film cracking. SiO2 700 may also be used as a mask for liquid phase crystal growth on Gallium Arsenide Substrates, or for a capping layer in group III-V semiconductor processing or for a back sealing layer prior to epitaxial silicon deposition in MOS applications. Filmtronics’ SiO2 film may also be used to getter metallic impurities from silicon. The submicroporous structure of the silicon dioxide film has the ability to getter metallic impurities from silicon surfaces at temperatures of 1050˚C to 1150˚C. Then the silicon slices are cooled at a rate of 1˚C to 3˚C per minute. SiO2 700 has excellent bonding to thermal SiO2, silicon and itself. Adhesion to CVD films containing phosphorous deteriorates with increasing phosphorous content of CVD film. Adhesion to aluminum depends on aluminum surface and cleanliness. There is a possibility of SiO2 700 crazing or cracking on aluminum features greater than few square microns upon curing at 400˚C due to poor adhesion or differences in coefficient of expansions. If this occurs, one of our spin-on glasses may be employed. See our SOG Catalogue. For smoothing uneven wafers topologies or for dielectric layer applications, SiO2 700 may be applied either before or after the deposition of a CVD glass layer as shown at top of next page.

PRODUCT DESCRIPTION


SPIN-ON GLASS 700 A & B

Etch Rate, Å/minute

Type of Etch SiO2 700 (400˚C) SiO2 700 (900˚C) Thermal SiO2

100:1 BOE, 20˚C 275 50 50 50:1 BOE, 20˚C 660 130 130 CF4 + O2 plasma 1730 1140 1100

CHF3 plasma 600 440 440

BOE stands for buffered oxide etch and is made by mixing 100 or 50 parts by volume of 40% NH4F solution in water with 1 part of 49% HF.

FILM PROPERTIES OF 700 SERIES SiO2 GLASS. CURE 700 FILM

Refractive index 425˚C, Air 1.45±0.002 Thickness variation (across wafer): <2% Dielectric constant (thermal SiO2=4.1)

425˚C, Air 600˚C, Oxygen 800˚C, Oxygen

6-7 5-6 4.1

Radial striations:

<1% (of Thickness

Film Shrinkage, % (from 150˚C to 425˚C)

425˚C, Air 15±2 Intrinsic film stress: 2x109 dynes cm2

Etch rate in 50:1 B.O.E. (relative to thermal oxide)

425˚C, air 600˚C, Oxygen 800˚C, Oxygen 800˚C, Steam

4.0 3.0 2.2 1.2

Coefficient of stress: Mobile ion contamination:

1x10-6K-1 (estimated) 5x1010 cm-2 (typical)

SiO2 films should be used in a well ventilated area to avoid inhalation of vapors as well as skin contact. Any standard dopant (or photoresist) spinner that is well ventilated can be used. No special ambient conditions are required.

1. The solution should be brought to room temperature 24 hours prior to spin-on application. 2. Dispense enough material on to the wafer to cover one-third to half of the wafer. 3. Spin the wafer for 20 seconds at 2000-6000 rpm to obtain the desired film thickness. 4. Prebake at 90˚C-100˚C for 10 minutes in air (this step is not necessary if the temperature is ramped in the cure step). 5. Cure the film at 400˚C-450˚C (in air) for 1 hour in an oven or on a hot plate. Higher cure temperature will improve film

properties. It is suggested that the spun glass films be cured for 15 minutes at 100˚C followed by 60 minutes at 400˚C depending on application of film.

Film Thickness As A Function of Spin-Speed (One hour cure at 400˚C)

Spin Speed, rpm 2000 3000 4000 5000 6000 SiO2 -700A Thickness, Å 2000 1620 1395 1210 1150 SiO2 -700B Thickness, Å 2970 2240 2100 1820 1675

PRODUCT DESCRIPTION


GOLD FILM Au-900 GOLD FILM Au-910

Gold is commonly used in the Semiconductor Industry as a lifetime modifier in silicon as well as a means of increasing surface conductivity. Minority lifetime modification may be achieved through base diffusion, emitter diffusion or emitter spiking. Fast switching transistors and diodes may be formed in this way. To increase conduction of the surface, a film of gold (solution 900) may be applied to the silicon substrate. (Wafers are cleaned in a 48% HF solution followed by a Dl rinse prior to diffusion to remove any oxides that may inhibit diffusion.) The wafer can be painted or spin coated with the gold solution at a spin speed of 500 to 3000 rpm for 10-15 seconds. The wafer then is air dried and heated at 300˚C for 15 minutes to form the pure gold film. If necessary, ethyl or isopropyl alcohol may be used to thin the solution. Films may also be painted on. In lifetime modification, silicon wafers are appropriately cleaned and are coated with a film of Au-900 or Au-910 gold solution and diffused. Diffusion is normally conducted in nitrogen or argon or hydrogen ambient. Diffusion in a dry hydrogen ambient yields a much more uniform lateral gold concentration than one performed in wet oxygen. For diffusing large amounts of silicon wafers simultaneously, wafers may be heated in the entrance of the diffusion tube to prevent smoking. Diffusion Data: Gold films were applied to slices at spin speed of 2200 rpm and diffused at a temperature of 800˚C using a nitrogen ambient. Wafers were removed at 6” per minute and cooled in air. The resulting surface concentration of gold was 4 x 1015 atoms/cm3. After diffusion, wafers may be cleaned in HF; boiling aqua regia may be used to remove any excess Gold on the surface.

Temperature (˚C)

Gold Saturating Solubility (Atoms/Cm3)

Diffusion Coefficient (cm2/sec)

600 1 X 1014 2 X 10-10 800 1 X 1015 6 X 10-9 1000 8 X 1015 4 X 10-8 1100 1 X 1016 8 X 10-8 1200 1 X 1016 1 X 10-7

Concentration of Gold Films are approximately 1.0 X 1020 atoms/cm3. This exceeds the amount of dopant impurity necessary to control minority carrier lifetime. The amount of Gold diffused into the wafer is controlled primarily by the process parameters, time and temperature. For gold diffusion best results are obtained by applying the Au900 to a lapped or as-cut wafer versus a polished or chem. Etched. The increase surface area of a lapped or as-cut wafer permits the gold to diffuse more uniformly.

PRODUCT DESCRIPTION


PLATINUM FILM Pt-920 PLATINUM FILM Pt-930

Platinum has been shown to introduce two deep impurity levels into silicon. Platinum films made from solutions Pt-920 and Pt-930 may be diffused into silicon as a means of modifying minority carrier lifetime or deposited as a thin film of platinum on a surface for conductive purposes in lieu of an evaporated platinum film. Some uses are base or emitter diffusion. Fast switching diodes and transistors may be formed through platinum diffusion. Pt920 has no SiO2, Pt930 has SiO2. Pt920 works best for fast switch rectifiers. Both Pt-920 and Pt-930 solutions may be applied as films to the surface of a silicon wafer by placing a few drops of solution on the substrate and spinning at a spin speed of 500-3000 rpm. Heat treatment is not necessary prior to diffusion. Large amounts of wafers being diffused may be heated in the mouth of the diffusion tube to prevent smoking. Films may also be painted on, or dip coated. For the formation of pure films of platinum, it is necessary to heat the spun on platinum film (920) at approximately 300˚C for 15 minutes. Diffusion may be effected in a nitrogen, argon, or hydrogen ambient. Best diffusion results are obtained using a lapped or as-cut silicon slice compared to a polished slice. The greater surface area of a lapped or as-cut silicon slice permits the platinum to diffuse more uniformly. Some diffusion data follows:

Temperature Platinum Solubility Diffusion Coefficient D, cm2/sec

tr nanoseconds Vf, Vr=5 ma P-N diode

800˚C 2 x 1014 4.5 x 10-8 100 900˚C 8 x 1014 3.0 x 10-7 10 1000˚C 1 x 1016 1.5 x 10-6 1

Both platinum films may be thinned with isopropyl or ethyl alcohol if necessary to modify characteristics of device. The concentration of the film exceeds the amount of dopant impurity necessary to control minority carrier lifetime. Therefore, the amount of Platinum or Gold diffused into the wafer is controlled primarily by process parameters, time and temperature. Diffusion in 20% hydrogen improves the diffusivity of Platinum. Spin: 1-2 ml dispense: 2000rpm; 15 seconds Pt-930 solution Cure: 150˚C; 1 hour in air Diffuse: To switching/gain desired; load back to back; 3” @ 1 liter/minute nitrogen Device Diff. Temp./Time Gain (beta)

@ 100mA 5V Breakdown Voltage (CEO) @ 5mA

Switching (T-off)

Control None 125-200 85-110 3.5-6 mu-sec Test 1 850˚C; 60minutes 60-100 100-140 1-3 mu-sec Test 2 900˚C; 60 minutes 40-80 120-160 750 nano sec Example: Device Type Process Location Coating Parameters T2L Prior to Base Diff. Backcoat 1150˚C 10-20-80 O2 – Steam – N2 Discretes Post Emitter Frontcoat 975˚C 15 minutes N2

PRODUCT DESCRIPTION


PLATINUM LIFETIME INFORMATION In recent years platinum has received renewed attention as a lifetime-control deep level impurity in silicon. Conflicting results have been reported in the literature (1, 2, 3), however, concerning the various energy levels of platinum as tabulated in Table 1. There appears to be a general agreement regarding two levels – one in the upper half of the bank gap at Ec-0.23±.03eV and another in the lower half at Ev-0.030±.03eV. The remaining levels noted are observed by some investigators but not by others. As few as two levels have been reported by Miller et al. (2) and as many as six levels by Evwaraye and Sun (3). This paper reports the results of identification of deep levels of platinum in Silicon using the conventional thermally stimulated current (TSC) and capacitance (TSCAP) measurements and a new technique of thermally stimulated field-effect transistor conductance measurement.

Table I. Comparison of Energy Levels of Platinum in Silicon.

(Energy value in eV represents separation from the nearest Band Edge)

Preparation of Test Devices

Examination of deep levels in the top half of the band-gap using TSC measurements requires a device which relies on electron emission to the conduction band. Either a p+-n diffused diode or a Schottky barrier diode on n-type silicon may be used for this purpose. A Schottky barrier diode was chosed in order to avoid the so-called process-induced defect that often results due to a high temperature boron diffusion which introduces two levels within the band gap, one at Ec-0.24±0.02eV and another at Ec-0.55±0.02eV (4.5). Since platinum has been shown by others (See Table I) to have a level very close to this upper gap energy level, we decided to avoid any high temperature boron diffusion and instead use a Schottky barrier diode which involved aluminum evaporation through a metal mask onto a 10 W-cm n-type silicon wafer. A 15 minute anneal at 500˚C in 80%N2 and 20% H2 was used in the fabrication of this device. For the examination of the platinum levels in the lower half of the bandgap, by the TSC technique, n+-p diodes were fabricated. For this purpose, n+ diffusions were performed from a PBr3 source at 1025˚C into a 3-5 W-cm p-type silicon wafers. Platinum was introduced into the respective wafers containing eh Schottky barrier diodes and the n+-p diodes by means of diffusion from a spin-on* source of platinum-silica mixture. This was spun-on the back side of the wafers and diffused at 900˚C for 1 hour in nitrogen. A moderate cooling time (~5 seconds) was used. No deliberate quenches wer processed with identical high temperature conditions but without the introduction of platinum. An FET test structure was also used for these measurements, as shown in Figure 1. The starting material for this device was 5um epitaxial 2-10 W-cm p-type Silicon on an n-type silicon substrate. The n+ gate and isolation diffusion was for 22 minutes at 1025˚C (PBr3 source) followed by a 30 minute oxidation at 1050˚C. This resulted in a 2.3µm junction depth and a sheet resistance of 15 ohms/square. The p+ source and drain diffusion was performed at 950˚C for 35 minutes using a low-temperature grade 93%BN source. The junction depth was approximately 1.5µm. *Platinum Silica Source form Filmtronics. Reprinted from Journal of Electronic Materials (Volume 7, Number 5, September 1978)

PRODUCT DESCRIPTION


Sources of Defects, Traps, and Recombination Centers

Oxygen is an important center in its many configurations in the silicon lattice. Its high concentration, rapid diffusion rate, and ready availability make it a likely participant with many defects and impurity atoms. Carbon, similarly to oxygen, is highly available and goes into the lattice as a single interstitial and as an interstitial-substitutional pair. Iron apparently is present in silicon material from most suppliers in saturation quantities (1015cm-3 at room temperature) [84-86]. It can be reproduced by float zoning or successive Czochralski pulls. Chromium [87] is another common transition metal [88-91] center. While copper [87] is a problem in its dispersed phase 9thermally quenched0, it tends to cluster and precipitate at dislocations or surfaces, making it relatively benign [32.88]. Many of the impurities do not become serious problems until the processed devices are irradiated with high-energy particles [92]. The resulting recoil atoms or subsequent knockon atoms may come to rest in the lattice distortion of the defect and form a relatively stable pair or triplet. Thus, the carbon-oxygen-vacancy (C-O-V) forms a dominant recombination center [93] in silicon at Ev + 0.138 eV, with a minority carrier capture cross section σn, of 10-12 to 10-15cm2. Similarly, oxygen and boron form a neutral interstitial pair at Ec -0.27 eV [93], a majority carrier trap, as do the oxygen-vacancy pair (A center) [94], the doubly charged divacancy [95.96], and other atomic configurations [97-100]. Gold [101-103] and platinum [104] form recombination centers. Recently, experiments have been conducted adding a host of metal atoms to silicon in order to assess their effect upon solar cell material as potential impurity remnants in a low-cost production process. It was found by Westinghouse Research Laboratories [88] that the worst lifetime killers are, in order of decreasing severity, molybdenum, titanium, vanadium, chromium, manganese, iron, aluminum, nickel, copper, magnesium, zinc, and calcium, with the last three being approximately on a par. Interestingly, there was no correlation between the lifetime measured on ingot starting material and the device lifetime of the finished solar cell, which will be discussed further on in the paper under the paragraph on processing effects. While this listing of centers is by no means exhausted [105-111], it provides some insight into the complexity of defect phenomena. During the last ten years, a great deal of progress has been made through the maturing of powerful electron spectrometry techniques, which complement the existing electron spin resonance methods of Corbett and Watkins and their co-workers [112-116]. These techniques include thermally stimulated capacitance or currents, pioneered by Sah and his group [117-120], with prolific participation by Buehler and Koyama [38, 121-123]. Deep-level transient spectroscopy was pioneered by Lang [124-125], Kimmerling [126], and Drevinsky [127]. An outgrowth of investigations of deep-level transient spectroscopy led to exploration of additional phenomena that tend to make defects more or less active, create additional centers, or aid recovery [128]. These are drift due to field-enhanced motion [129], configurational effects due to polarization of the defect complex or excitation [130], and, finally, recombination-enhanced defect reactions [131]. The last of these is a process that could be responsible for injection-laser and tunnel-diode degradation, while it is also thought to eliminate certain defects athermally. The basis of the mechanism is the momentum deposited at a recombination center by the indirect transition of the participating charge carriers. The amount of energy absorbed by the defect site depends upon its location in momentum space and on the size of the energy gap. If the defect activation energy for motion is less than the energy deposited or even close to it, the probability for quasi-annealing or true athermal annealing is adequate. This has been observed by Kimerling [132, 133].

Effects of Processing It was pointed out previously that the electrical properties of the starting material may be irrelevant to the device characteristics. The reason for this is the dramatic effect of particular fabrication steps upon the material quality. Aside from potentially allowing impurities to be added at high temperatures because of poor laboratory practices, the effect upon the distribution of already existing impurities in the lattice can be severe. High temperatures cause most atomic species in a crystal to disperse, in addition to increasing the lattice vacancy concentration to the equilibrium value specified for that temperature. When the temperature is rapidly dropped during a radiation quench, because of rapid withdrawal from the furnace in order to meet production quotas, the material does not have time to come to thermal equilibrium, and the high-temperature disorder-dispersed impurity phase and vacancy-interstitial concentrations are frozen into the crystal [84-85]. However, a slow cooling rate of only a few degrees per minute will cause through equilibrium, with resulting beneficial annealing effects [32, 134]. Also, holding the specimen at a specific temperature for 10 to 30 minutes will help in recovering or retaining long lifetimes. Gettering steps have similar beneficial effects [135].

Reprinted From Lifetime Factors in Silicon.

PRODUCT DESCRIPTION


Lifetime Thermal Processing Slow cooling of silicon wafers following high-temperature processing cycles is well known to be mandatory for the preservation of lifetime. The number of lattice defects in thermal equilibrium is expected to increase exponentially with temperature according to Boltzmann’s statistics. A quantitative knowledge of the equilibrium trap density is all that a process specialist needs in order to determine when slow cooling is necessary and to what final temperature. Rapid cooling “freezes” the thermally generated traps at their equilibrium concentration, and the trap density can be determined by the relationship Nt = (τr σνth)-1 . The relationship between τr and the quench temperature is shown in Fig. 1. The temperature range above 700˚C is completely dominated by thermally generated traps, and an Arrhenius plot of 1/ τr Versus 1/T yields an activation energy equal to 1.48 eV. The activation energy is near to that necessary for the generation of divacancies. The range below 700˚C becomes increasingly dominated by recombination traps as a result of impurities initially present in the lattice. Generally the curve indicates that very few semiconductor devices are so insensitive to tr that no concern for slow cooling is necessary. Phosphorous gettering is commonly used to remove impurities inescapably introduced during prior oxidation and diffusion procedures. The concept of cascading multiple gettering cycles in an intriguing scheme, because coalesced contamination in the n+ layer can be permanently separated from the wafer by chemical etching. The results in Fig. 2 demonstrate that this intuitive concept is naïve, at least for the case of chromium impurities. Inadvertent contamination between gettering cycles is ruled out as the reason for the decay in lifetime for N>1, because control specimens without chromium did not experience degradation. The phenomenon is tentatively attributed to impurity pinning and increased capture cross section, possible as a result of interaction with oxygen in the silicon.

PRODUCT DESCRIPTION


EXPERIMENTAL CADMIUM FILM Cd-960 Cadmium Silicon dioxide spin on dopants (consisting of predetermined amounts of dopant i.e., Cd atoms in a SiO2 solution) find application in the diffusion and fabrication of P/N junctions when utilizing N type substrates such as GaAs, GaP, and GaAsP. Concentration of these atoms in a spun film will range upwards of 1020 atom/cm3 or greater. The constituent (SiO2) in these solutions precludes or minimizes possible surface damage to the substrates via adverse chemical effects. Advantages: This is a spin film source of great uniformity, reproducibility and control. Concentration of atoms: The concentrations of Cd atoms and hence the concentration may be reduced almost linearly with addition of dopant free SiO2 solution. Wafer Preparation: Wafers may be prepared for application of spin dopants by 5% HF rinse for 5-10 seconds followed by distilled H2O and isopropanol rinses, and spun dry. Application: Cadmium film consists basically of Cadmium and SiO2 in a solution of organic solvents, all in the appropriate ratios and amounts. If required, the concentration of dopant solution may be reduced through addition of predetermined amounts of the SiO2 undoped-spin-on solution. Thinner layers of the spun stratum may be achieved through addition of ethyl alcohol etc. and/or increasing spin deposition speeds if this is the mode of dopant application. Application of dopant can be made via: 1. Spin-on process; 2. Spray process; and 3. “Paint On process.” In the latter process the thickest films are possible. However, care must be exercised to avoid crazing and cracking the thicker films. Thinning with ethyl alcohol can reduce this problem. Diffusion Results: Some typical values of diffusion when using GaAs with a background concentration of 5 x 1016 atom/cm3 are as follows after steps 1-5 are completed;*

1. Apply a puddle of CdSiO2 dopant 0.50 ml. 2. Spin at 3000 rpm at 70˚F, 60% RH ambient 3. Diffusion ambient – N2. 4. Diffuse at temperature 850˚C 5. Diffusion time – 15 minutes 6. *Resulting surface concentration Co-1 x 1018 atoms/cm3 7. *Resulting junction depth Xj is – 3.0 microns.

Post Diffusion Clean Up: Removal of the Cadmium doped SiO2 layer is achieved via a 10% HF soak for approximately 2 minutes at room temperature. Further control of the doping process is realized through annealing. Using (RTP) Rapid Thermal Processing yields shallow junction depths. The ambient during annealing also affects dopant diffusion. Plasma Enhanced Chemical Vapor Deposition (PECVD) SiO2 layers can act as a capping layer and avoid Arsenic and Gallium losses from the substrate. The SOG Films are less dense than the PECVD Films and may allow an Arsenic over-pressure ambient to influence the diffusion from an SOG over layer. Cadmium Film fabricated with Gallium atoms, Arsenic atoms or any combination of the above are available for research, the Arsenic or Gallium may prevent losses from the substrate during diffusion.

PRODUCT DESCRIPTION


EXPERIMENTAL SELENIUM FILM Se-965 Selenium silicon dioxide spin-on dopants are used in the fabrication of P/N junction in GaAs, GaP, GaAsP, etc. substrates. This material consists of about 1020 atoms/cm3 in a SiO2 solution. It is essentially applied to the substrate (i.e. GaAs) – dried, baked and diffused. Advantages: The selenium film solutions provide tightly controlled dopant sources with high reproducibility, accuracy, and utility. This material lends itself nicely to devices with shallow junction depths. Concentration of atoms: The solution may be varied with addition of an undoped SiO2 solution. A 2-1 addition of SiO2 – 700A solution to dopant reduces concentration approximately by a half. Wafer Preparation: Wafers may be prepared for application of spin dopants by a 5% HF rinse for 5-10 seconds followed by distilled H2O and acetone rinses. Application: Selenium film consists basically of selenium and SiO2 in a solution of organic solvents all in the appropriate ratios and amounts. If required, the concentration of dopant solution may be reduced through addition of predetermined amounts of the SiO2 undoped spin on solution. Thinner layers of the spun stratum may be achieved through addition of ethyl alcohol etc., and/or increasing spin deposition speeds if this is the mode of dopant application. Application of dopant can be made via: 1. Spin-on process; 2. Spray process; and 3. “Paint on” process. In the latter process the thickest films are possible. However, care must be exercised to avoid crazing and cracking in the thicker films. Thinning with ethyl alcohol can reduce this problem. Diffusion results when utilizing the following:

1. Wafers – GaAs 2. Wafer concentration background – 5 x 1016 atoms/cm2 3. Dopant application – apply a puddle SeSiO2 onto wafer about 0.50 ml. 4. Spin at 3000 rpm in a 70˚F, 60% RH ambient 5. Diffusion ambient – N2 & H2 12:1 by volume 6. Diffusion temperature - 1000˚C. 7. Diffusion time – 15 minutes 8. Resulting surface concentration – 6 x 1018 atoms/cm3 9. Resulting junction depth – 1.3 microns

Further control of the doping process is realized through annealing. Using (RTP) Rapid Thermal Processing yields shallow junction depths. The ambient during annealing also affects dopant diffusion. Plasma Enhanced Chemical Vapor Deposition (PECVD) SiO2 layers can act as a capping layer and avoid Arsenic and Gallium losses from the substrate. The SOG Films are less dense than the PECVD Films and may allow an Arsenic over-pressure ambient to influence the diffusion from an SOG over layer. Selenium Film fabricated with Arsenic and Gallium or any other combination of the above are available for research. The Arsenic or Gallium may prevent losses from the substrate during diffusion. Post Diffusion Clean Up: Removal of the Tin doped SiO2 layer is achieved via a 10% HF soak for approximately 2 minutes at room temperature.

PRODUCT DESCRIPTION


EXPERIMENTAL TIN FILM Sn-970 In LED (light emitting diode) work utilizing GaAs substrates the tin film finds usage as the donor source for heavily doped N+ regions, where the P/N regions are fabricated with Zn-SiO2 spin-on dopants (refer to Zinc film data sheet for actual values). A 900˚C diffusion for 16 minutes, produces a junction depth of 1.6 microns and a sheet resistivity of 34.5 ohm/square. In finished device form when employing gold as the P contact Vf = 1.6 volts at 10 milliamps and Vr = 14 volts. Advantages: The tin spin-on dopants provide tightly controlled dopant sources with high reproducibility, accuracy, and utility. This material lends itself nicely to devices with shallow junction depths. Wafer Preparation: Wafers may be prepared for application of spin dopants by 5% HF rinse for 5-10 seconds followed by distilled H2O and acetone rinses. Application: Selenium film consists basically of selenium and SiO2 in a solution of organic solvents all in the appropriate ratios and amounts. If required, the concentration of dopant solution may be reduced through addition of predetermined amounts of the SiO2 undoped spin on solution. Thinner layers of the spun stratum may be achieved through addition of ethyl alcohol etc., and/or increasing spin deposition speeds if this is the mode of dopant application. Application of dopant can be made via: 1. Spin-on process; 2. Spray process; and 3. “Paint on” process. In the latter process the thickest films are possible. However, care must be exercised to avoid crazing and cracking in the thicker films. Thinning with ethyl alcohol can reduce this problem. Diffusion results when utilizing following:

1. Wafers – GaAs 2. Wafer concentration background – 5 x 1016 atoms/cm2 3. Dopant application – apply a puddle SeSiO2 onto wafer about 0.50 ml. 4. Spin at 3000 rpm in a 70˚F, 60% RH ambient 5. Diffusion ambient – N2 & H2 12:1 by volume 6. Diffusion temperature - 1000˚C. 7. Diffusion time – 15 minutes 8. Resulting surface concentration – 6 x 1018 atoms/cm3 9. Resulting junction depth – 1.3 microns

Further control of the doping process is realized through annealing. Using (RTP) Rapid Thermal Processing yields shallow junction depths. The ambient during annealing also affects dopant diffusion. Plasma Enhanced Chemical Vapor Deposition (PECVD) SiO2 layers can act as a capping layer and avoid Arsenic and Gallium losses from the substrate. The SOG Films are less dense than the PECVD Films and may allow an Arsenic over-pressure ambient to influence the diffusion from an SOG over layer. Selenium Film fabricated with Arsenic and Gallium or any other combination of the above are available for research. The Arsenic or Gallium may prevent losses from the substrate during diffusion. Post Diffusion Clean Up: Removal of the Tin doped SiO2 layer is achieved via a 10% HF soak for approximately 2 minutes at room temperature.

PRODUCT DESCRIPTION


EXPERIMENTAL TIN FILM Sn-970 In LED (light emitting diode) work utilizing GaAs substrates the tin film finds usage as the donor source for heavily doped N+ regions, where the P/N regions are fabricated with Zn-SiO2 spin-on dopants (refer to Zinc film data sheet for actual values). A 900˚C diffusion for 16 minutes, produces a junction depth of 1.6 microns and a sheet resistivity of 34.5 ohm/square. In finished device form when employing gold as the P contact Vf = 1.6 volts at 10 milliamps and Vr = 14 volts. Advantages: The tin spin-on dopants provide tightly controlled dopant sources with high reproducibility, accuracy, and utility. This material lends itself nicely to devices with shallow junction depths. Wafer Preparation: Wafers may be prepared for application of spin dopants by 5% HF rinse for 5-10 seconds followed by distilled H2O and acetone rinses. Application: Tin film consists basically of selenium and SiO2 in a solution of organic solvents all in the appropriate ratios and amounts. If required, the concentration of dopant solution may be reduced through addition of predetermined amounts of the SiO2 undoped spin on solution. Thinner layers of the spun stratum may be achieved through addition of ethyl alcohol etc., and/or increasing spin deposition speeds if this is the mode of dopant application. Application of dopant can be made via: 1. Spin-on process; 2. Spray process; and 3. “Paint on” process. In the latter process the thickest films are possible. However, care must be exercised to avoid crazing and cracking in the thicker films. Thinning with ethyl alcohol can reduce this problem. Typical Process – When employing a GaAsP substrate it is suggested:

1. SnSiO2 spin-on dopants be applied with dropper in the amount of 0.4 ml/cm2 2. Spun at 1100 rpm for 14 seconds 3. Baked at 200˚C for 15 minutes in air 4. Diffused at 850˚C - 900˚C – a diffusion at 900˚C in a Ar atmosphere into a GaAsP wafer for 15

minutes would yield a surface carrier concentration of Co-1-2 x 1019 atoms/cm3 and a junction depth Xj=0.19 microns

Post Diffusion Clean Up: Removal of the Tin doped SiO2 layer is achieved via a 10% HF soak for approximately 2 minutes at room temperature. Surface Damage: It is suggested an interface of SiO2 film be interposed and heat treated substrate prior to deposition of the (dopant) tin film. In this manner damage is minimized and diffusion enhanced. Further control of the doping process is realized through annealing. Using (RTP) Rapid Thermal Processing yields shallow junction depths. The ambient during annealing also affects dopant diffusion. Plasma Enhanced Chemical Vapor Deposition (PECVD) SiO2 layers can act as a capping layer and avoid Arsenic and Gallium losses from the substrate. The SOG Films are less dense than the PECVD Films and may allow an Arsenic over-pressure ambient to influence the diffusion from an SOG over layer. Tin Film fabricated with Arsenic and Gallium or any other combination of the above are available for research. The Arsenic or Gallium may prevent losses from the substrate during diffusion.

PRODUCT DESCRIPTION


EXPERIMENTAL ZINC FILM Zn-980 Junctions may be fabricated in III, V materials such as Gallium Arsenide and Gallium Phosphide as well as Gallium Arsenic Phosphide compounds when utilizing a zinc dopant in a spin-on solution consisting of zinc, and appropriate diluents, etc. The actual diffusion process essentially entails diffusion of Zn through a SiO2 layer and then into the host wafer, e.g.: GaAs, etc. The function of the interface or SiO2 stratum is to preclude adverse chemical or physical effects which may damage the substrate. Advantages: The tin spin-on dopants provide tightly controlled dopant sources with high reproducibility, accuracy, and utility. This material lends itself nicely to devices with shallow junction depths. Wafer Preparation: Wafers may be prepared for application of spin dopants by 5% HF rinse for 5-10 seconds followed by distilled H2O and acetone rinses. Application: Zinc-SiO2 spin-on dopants consist basically of zinc and SiO2 in a solution of organic solvents all in the appropriate ratios and amounts. If required the concentration of dopant solution may be reduced through addition of predetermined amounts of the SiO2 – undoped-spin-on solutions. Thinner layers of the spun stratum may be achieved through addition of ethyl alcohol etc. and/or increasing spin deposition speeds if this is the mode of dopant application. Application of dopant can be made via: 1. Spin-on process; 2. Spray process; and 3. “Paint on” process. In the latter process the thickest films are possible. However, care must be exercised to avoid crazing and cracking in the thicker films. Thinning with ethyl alcohol can reduce this problem. Diffusion Notes: Diffusion: The zinc in SiO2 spin dopant when spun at about 3000 rpm onto a Gallium Arsenide wafer (doped to about 5 x 1016 atoms per centimeter cube) yields the following when diffused at 850˚C for 15 minutes in nitrogen:

1. Diffusion depth Xj – 3.9-4.1 microns 2. Co (surface concentration) – 4.6 x 1018 atoms/cm3

Diffusion (Wafer Positioning) – Wafers may be diffused when stacked on edge in slotted Quartz boats or when laid flat. Special Zinc – Silica Dopants – Special zinc spin-on dopants which are used in conjunction with SiO2 spin-on films have been developed for (heavily doped “P” regions) in light emitting diode usage when utilizing Gallium Arsenide Phosphide epitaxial type wafers. Application – These films may be handled in the following manner:

1. Apply SiO2 liquid spin-on solution (to substrate) spin to achieve desired thickness 2. Heat treat SiO2 layer in air to stabilize and densify. This step precludes cracking etc. in subsequent operations. (A temperature bake of

250˚C - 300˚C in excess of one hour achieves these ends and simultaneously minimizes moisture absorbed.) 3. Apply Zinc SiO2 spin dopant to heat treated SiO2 film. Bake at 250˚C - 300˚C for 10 minutes. Wafers are now ready for diffusion.

Diffusion – Diffuse above wafers in an argon ambient. For shallow junctions, temperatures of 800˚C-950˚C are optimum. Below are some results with 15 minute diffusions at 850˚C and 900˚C for utilizing above silica film (underlay) and ZnSiO2 overlay systems. SiO2 Film Thickness

Zinc SiO2 Film Thickness

Xj Microns 850˚C Rs /

Xj Microns 900˚C Rs /

2000 Å 1000 Å .9 75 1.6 55 1500 Å 1000 Å .9 55 1.6 40 * Spin speeds of 5000 rpm and 3000 rpm yield dried film thickness in SiO2 of 1000 Å and 2000 Å respectively, and 1000 Å in the case of Zn films Note: The SiO2 film and Zn dopants are specially fabricated and deposited in the above order to minimize any crazing, cracking or thermal mismatch. The SiO2 also enhances diffusion of a relatively low concentration of Zinc (thereby minimized wafer surface disturbance) while facilitating high surface carrier concentration. Post Diffusion Clean Up: Removal of the Tin doped SiO2 layer is achieved via a 10% HF soak for approximately 2 minutes at room temperature. Further control of the doping process is realized through annealing. Using (RTP) Rapid Thermal Processing yields shallow junction depths. The ambient during annealing also affects dopant diffusion. Plasma Enhanced Chemical Vapor Deposition (PECVD) SiO2 layers can act as a capping layer and avoid Arsenic and Gallium losses from the substrate. The SOG Films are less dense than the PECVD Films and may allow an Arsenic over-pressure ambient to influence the diffusion from an SOG over layer. Zinc Film with Arsenic and Gallium as well as Zinc are available on request. These films may possibly avoid any Arsenic or Gallium losses from the GaAs substrate.

QUALITY CONTROL & EQUIPMENT


SPIN-ON DOPANT QUALITY CONTROL MEASUREMENTS

1. Thickness – Measured by spinning SOG sample at specified rpm (3000) for 25 seconds at 23˚C - 25˚C. The coated wafer is then baked at 150˚C for 60 seconds then 420˚C for 60 minutes in nitrogen. The coating thickness is measured using a Nanospec AFT at a specified index of refraction. Measurements are taken at 4 points on a wafer – center, top-center, flat, left and right – and averaged. Uniformity is about +/- 2%. Thickness range is 400 to 10,000Å.

2. Viscosity – This is measured using a Brookfield Viscometer in a constant temperature bath at 25˚C. Three measurements are obtained and averaged. Variation is about 2%. Product viscosities range from 0.50 to 100 cp.

3. Visual Test – Solution is checked for clarity. 4. Elemental Analysis – Impurity is determined by use of inductively coupled plasma analysis.

Elements Measured Typical Reading (ppm) SOD Max Spec (ppm)

K 0.025 0.05 Ca 0.020 0.05 Mg 0.002 0.05 Mn 0.0002 0.05 Ni 0.0005 0.05 Cu 0.0004 0.05 Fe 0.0005 0.05 Na 0.015 0.05 Cr 0.0002 0.05

Other elements available upon special request. 5. Solid Content of Solution – A 10 ml sample is pipetted into a platinum crucible – weight is recorded. The

solvent is evaporated at 150˚C for 2 hours. Sample mass is then recorded and test repeated with 3 readings averaged. Variation is +/- 1%. Product solid contents range from 2.0% to 15%.

6. Index of Refraction – Using a Rudolph Ellipsometer 3 readings are taken and averaged. Variation is 1%. Range is 1.38-1.48.

7. Water Content – Using a Karl Fischer System 10 ml of sample is introduced into system. The system determines the percent water.

Additional Periodic Measurements Include: 1. I.R. Spectroscopy 2. Etch Rates – Wet and Plasma 3. Electrical Parameters – Capacitance, Resistivity and Breakdown Voltages 4. Density 5. Diffusion and Sheet Resistances

Additional Equipment Used for Measurement:

1. Particle Counter – PMS Liquid Particle Counter – 0.2 micron sensitivity 2. Scanning Electron Microscope 3. Hewlett Packard Oscilliscopes 4. Heithley 4 Point Probes – 2 systems 5. Spin-Coating Equipment 6. Diffusion Furnaces – 7 tubes available 7. ADE Non Contact Resistivity and Thickness Gauge 8. Mettler Analytical Balances 9. PH Meter – Box Furnaces – HPLC – A.A,. Elipsometers 10. Karl Fishcer Titration





PRODUCT PRICING


Please contact Filmtronics for pricing information.

Ph.: (724) 352-3790

FAX: (724) 352-1772

E-Mail: [email protected]

FILMTRONICS SPIN ON SOLUTIONS CURRENT PRICE LIST

125 ml 4 oz.

16 x 4 oz.

1000 ml 32 oz.

6 x 32 oz

Aluminum Film Aluminum Boron Film Aluminum Gallium Film Antimony Film Arsenic Film Boron Film Gallium Film Gallium Boron Film Gold Film Phosphorous Film Phosphorous Film/Gold Platinum Film Silicon Dioxide Film Zinc Film Cadmium Film Selenium Film Tin Film Note: Custom formulations are available upon request. General Quotation Terms: 1. Terms are EXWORKS, Butler, PA, Net 30 days. 2. Prices are per unit and in U.S. Dollars. 3. There is no tax on our products; prices are as quoted. 4. Shipment 48 hours after receipt of order. 5. Shipping charges will be determined by your scheduling and are generally air freight.

Documents

Spin-On Diffusants Catalog 6