Cleaning & Surface Preparation Manual

Cleaning & Surface Preparation ManualFor Silicon Carbide Semiconductor Components

2 COORSTEK.COM

Table of Contents

Initial Clean for New Product – All Processes 3

Surface Preparation

Atmospheric/Oxidation & Drive-In 4

LPCVD Nitride/Poly/TEOS 5

Preventative Maintenance Clean



Appendix A – Cleaning Processes 8

Initial Clean for New Products for All Processes

Preventative Maintenance Clean for Atmospheric/Oxidation & Drive-In

Preventative Maintenance Clean for LPCVD Nitride

Preventative Maintenance Clean for LPCVD Poly

Preventative Maintenance Clean for LPCVD TEOS

Appendix B – Rinsing 8

Appendix C – Drying 9

Air Dry

Oven Dry

Alternate Drying Options

Appendix D – Install In Furnace 10

Appendix E – Surface Preparation



Appendix F – RTI® Ready-To-Install Components 12

HOW TO USE THIS MANUALThis manual provides an overview of CoorsTek's recommended cleaning and surface preparation methods using easy-to-follow flow charts. Additional detail and explanations can be found in the appendices.

This manual is not intended to address all aspects of fab-specific processes. Please contact your CoorsTek representative to discuss solutions to your unique situation.

3+1 774 317 2600

INITIAL CLEAN SURFACE PREP MAINTENANCE

1 WET CLEAN HF:DI 1:4 for 1 hour

2 RINSE 4 hours in flowing DI water

3 AIR DRY Until no visible moisture remains on the surface

4

OVEN DRY 4 hours at 150° C

ALTERNATE DRY 24 hours at room temperature

The steps above can be eliminated by ordering our RTI® components (see page 12)

5 INSTALL IN FURNACE

6

BEGIN SURFACE PREPARATION

Prepare SiC components for the processing of silicon production wafers for:

Atmospheric/Oxidation & Drive-In (see page 4)

Nitride/Poly/TEOS (see page 5)

Initial Clean for New ProductAll Processes

Initial Clean

Insertion Rates

800°C 100mm/min

700°C 125mm/min

600°C 150mm/min

500°C 180mm/min

400°C 200mm/min

< 400°C unlimited mm/min

4 COORSTEK.COM

Cleaning & Surface Preparation Manual

Surface PreparationAtmospheric / Oxidation & Drive-In

Surface Prep

1 WET CLEAN COMPLETE (see page 3)

2 INSTALLED IN FURNACE COMPLETE (see page 3)

3 RAMP TO 700°C IN DRY O2

4 RAMP TO 1100°C IN DRY O2 AND 6% HCI OR EQUIVALENT

5 RAMP TO 1200°C IN DRY O2 AND 3% HCI OR EQUIVALENT

6 SOAK 1 Hour at 1200°C

7 DISCONTINUE CHLORINE SOURCE Purge 10 Minutes with Dry O2 at 1200°C

8 STEAM 16 Hours at 1200°C (6 Hours if CVD Coated)

9 COOL In Dry O2 at 10°C / Minute or Less

10 PROCESS

5+1 774 317 2600


Surface PreparationLPCVD Nitride/Poly/TEOS

Surface Prep

1 WET CLEAN COMPLETE (see page 3)

2 INSTALLED IN FURNACE COMPLETE (see page 3)

3 RAMP TO DEPOSITION TEMPERATURE 10°C/minute maximum

4 PRE-COAT

5 PROCESS

6 COORSTEK.COM


Preventative Maintenance CleanAtmospheric / Oxidation & Drive-In

Maintenance

1 TYPICAL PREVENTATIVE MAINTENANCE INTERVAL 12 Months

2WET CLEAN HF:DI 1:4 12 Hours Minimum

3 RINSE 4 Hours in Flowing DI Water

4 AIR DRY Until No Visible Moisture Remains on the Surface

5 OVEN DRY 4 hours at 150°C

ALTERNATE DRY 24 Hours at Room Temperature


7 SURFACE PREPARATION For Atmosphere / Oxidation & Drive-In

7+1 774 317 2600


Preventative Maintenance CleanLPCVD Nitride / Poly / TEOS

Maintenance

1

WET CLEAN NITRIDE 49% concentrated HF 12 hours minimum No danger of over-etching

WET CLEAN POLY DI:HF:HNO3 2:1:3 Until reaction stops

WET CLEAN TEOS 49% concentrated HF 12 hours minimum

2 RINSE 8 hours in flowing DI water

3 VISUALLY INSPECT For complete deposition removal

4 REPEAT Clean and rinse if necessary

5 AIR DRY Until no visible moisture remains on surface

6 OVEN DRY 4 hours at 150°C

7 ALTERNATE DRY 24 hours at room temperature


9 SURFACE PREPARATION For LPCVD Nitride/Poly/TEOS

8 COORSTEK.COM

INITIAL CLEAN FOR NEW PRODUCTS FOR ALL PROCESSES Wet CleanRecommended procedure: HF:DI* 1:4 for one hour.

Other acceptable wet cleaning solutions can include HF and/or NH40H solutions. HF solutions can be combined with equal amounts of HCI when available, e.g., HF:HCI:H20 = 1:1:4. A ratio of 1:1:10 is also acceptable.

Do not use combined HF and HNO3 acids if SiC components are not CVD coated.

The combination of HF and HNO3 acids attacks silicon and can leach the silicon from non-CVD coated silicon carbide components. CVD silicon carbide coatings protect the silicon phase from HF:HNO3 attack.

*DI always refers to Deionized water. All ratios start with 49% concentrated HF.

PREVENTATIVE MAINTENANCE CLEAN FOR ATMOSPHERIC/OXIDATION & DRIVE-IN Frequency Of Preventative Maintenance CleaningCleaning frequency will be based on particulate and purity considerations. On average, PMs are done once per year. If weekly or biweekly system purges are run with a CI ion source such as DCA or HCI, leave components in the furnace to benefit from this additional cleaning.

Wet CleanRecommended procedure: HF:DI 1:4 for 12 hours. Other acceptable wet cleaning solutions could include HF and/or NH40H solutions. HF solutions should be combined with equal amounts of HCI when available, e.g., HF:HCI:DI = 1:1:4. A ratio of 1:1:10 is also acceptable.

The etch rate of oxide is approximately 211µm/hour using 10% HF solution.

PREVENTATIVE MAINTENANCE CLEAN FOR LPCVD NITRIDE Frequency Of Preventative Maintenance Cleaning• Cantilevers – Can accommodate up to 500,000Å without flaking.• Boats – Based on slot width and/or particulate considerations.• Horizontal Liners – Typically more than 2 times cantilever service life.

Wet Clean - 49% Concentrated HFRecommended Procedure: Etch in concentrated HF (49% HF) for a minimum of 12 hours.

For deposition thicknesses greater than 50µm, cleaning in concentrated HF up to 24 hours may be required. Etch rate of the

Appendix A Cleaning Processes

silicon nitride deposition is slow (1.8 - 3.6 µm per hour). A minimum of 12 hours is required as the nitride is removed by a sheeting action, as opposed to dissolution of the deposition. There is no danger of “over-etching.”

Note: Two extra hours of soak time are required once the original color of

the component is restored.

PREVENTATIVE MAINTENANCE CLEAN FOR LPCVD POLY

Frequency Of Preventative Maintenance Cleaning• Cantilevers – Can often accommodate

up to 5 million Å before removal.*• Boats – Based on slot width.• Other Products – Same as cantilevers.*

*Note that cantilevers and horizontal furnace liners in LPCVD Poly

operations are not normally cleaned and reused. There is risk of

overetching the polysilicon from the part and/or leaving residual acid. The

PM interval is usually greater than 1 year.

WET CLEAN - DI:HF:HN03 2:1:3Recommended: Etch in 2:1:3 DI:HF:HNO3 until reaction stops.

Note: Precautions must be taken to avoid etching silicon out of the structure.

Best practices include:a. Use components with a CVD SiC to act as an etch stop.b. Protect paddle handle interiors from the etch solution

(the insides of paddle handles are not CVO coated and must always be protected from HF:HNO3 etching).

c. Avoid stacking boats during wet clean. Silicon carbide is very abrasive and stacking can damage CVO coating.

PREVENTATIVE MAINTENANCE CLEAN FOR LPCVD TEOS

Wet Clean – 49% Concentrated HFRecommended procedure: HF:Dl 1:4 for 12 hours. Other acceptable wet cleaning solutions could include HF and/or NH40H solutions. HF solutions can be combined with equal amounts of HCI when available, e.g., HF:HCI:DI = 1:1:4. A ratio of 1:1:10 is also acceptable.

HF solutions should have an equal amount of HCI when available, e.g., HF:HCI:DI = 1:1:4. A ratio of 1:1:10 is also acceptable.

The etch rate of TEOS is approximately 2µm/hour using 10% HF solution.

9+1 774 317 2600

Mod

ulus

of R

uptu

re (

MPa

)

Siliconized Leached

250

200

150

100

50

0

Strength of Recrystallized Silicon Carbide®

Siliconized Silicon Carbide

CVD Coated Siliconized Silicon Carbide

Before Use Poly Deposition

After HF:HNO3 Acid

Strip

Second Poly Deposition

After Second HF: HNO3 Acid Strip

Polysilicon Deposition and Wet Clean Effects

Insertion Rates (mm/min)

800°C 700°C 600°C 500°C 400°C >400°C

100 125 150 180 200 unlimited

CVD SiC

Note the depth of Silicon acid leach Note the depth of Silicon

acid leach

Appendix B Rinsing

Appendix C Drying

Recommended Procedure: Rinse in flowing DI water for 4 hours.

When cleaning in concentrated HF (49%), rinse a minimum of 8 hours in flowing DI water. Rinsing with DI water is critical to removing residual acids from the surface of cleaned products.

Ideal rinsing is achieved when the surface of the component is continually exposed to fresh DI water. This can be achieved by various methods including flowing DI water baths, DI water cascading baths and DI water shower systems.

AIR DRYRecommended Procedure: Dry until no visible moisture remains on the surface, before placing in dryer oven.

OVEN DRYRecommended Procedure: Oven dry for 4 hours at 150°C.

Proper drying of components after cleaning is necessary to remove all trapped moisture both on and in the structure of the silicon carbide. At 374°C, an absolute pressure of 225 atm results in H20 and H2O vapors. Rapid ramp rates can result in conversion of any residual water to steam. The volume expansion associated with the water-to-steam conversion can lead to damage to the components. For this reason, it is necessary to completely dry the component. The recommended drying method dries the component at a temperature sufficient to remove all trapped moisture.

Therefore, after air drying, a drying procedure of 4 hours at l50°C is necessary to remove all water and is strongly recommended as the desirable drying procedure when possible.

ALTERNATE DRYING OPTIONSAlthough drying at 150°C for 4 hours is the recommended drying method when possible, the following are alternative drying procedures that can be used after the initial air dry step if the recommended oven-dry method is not possible. These methods can be used separately or in combination.

• Dry 24 hours at room temperature.

and/or• After 12 hours at room temperature, dry in the Process Tube

at 150-200°C for 1 hour. Ramp from room temperature to 200°C - should be at a maximum rate of 5°C / minute.

10 COORSTEK.COM

LPCVD NITRIDE/POLY/TEOS

RAMP TO DEPOSITION TEMPERATURERamp at a maximum ramp rate of 10°C/minute to deposition temperature

PRE-COATNitride: A pre-coat layer consisting of 1-2 runs of silicon nitride is necessary. A deposition thickness of 5000Å may be required.

Poly: A pre-coat layer consisting of 1-2 runs of polysilicon is necessary. A deposition thickness of 5000Å may be required.

A Si3N4 layer (approximately 10,000Å) can be pre-deposited to act as an etch stop if components with CVD SiC coating are not being used.

TEOS: A pre-coat layer consisting of 1-2 runs of TEOS is necessary. A deposition thickness of 5000Å may be required.

ATMOSPHERIC/OXIDATION & DRIVE-IN

HIGH TEMPERATURE CHLORINE (CI-) CLEANING AND OXIDE GROWTHThis applies to CVD SiC coated and non-CVD coated Recrystallized Silicon Carbide. A shorter oxidation time is required for CVD SiC coated SiC.

Note: For customers who do not have the capability to do high temperature

chlorine cleaning, CoorsTek offers optional hot HCI cleaning.

RAMP TO 800°C DRY O2Under flowing dry 02, ramp CoorsTek component to 800°C at recommended insertion and ramp rates.

RAMP FROM 800°C TO 1100°C DRY O2 + 6% HCIAt 800°C, add 6% HCI or 3% DCE/TransLC or 2% DCA so that impurities can be removed during heat-up as well as at full temperature.* When ramping from 800°C to 1100°C, a ramp rate of 5°C to 10°C is required.

Note: For 6% HCI, run HCI at 240 ml/min while running dry O2 at 4 l/min. For

2% DCA, run 300 ml/min N2 through the DCA bubbler at 25°C while running

dry O2 at 4 l/min.

*Do not start CI- source below 800°C because of unwanted products of

decomposition. Heat as closely as possible to the 10°C/minute rate. Slower

heating may result in excessive oxide growth before the impurities are

removed. Faster heating may result in thermal shock damage.

RAMP FROM 1100°C TO 1200°C DRY O2 + 3% HCIAt 1100°C, reduce HCI to 3% or DCE/TransLC to 1.5% or DCA to 1%.* Heat to 1200°C if possible, or at least 50° higher than intended process temperature (minimum 1100°C).

*Higher levels of CI- in these conditions can result in a reaction with Si or SiC

to produce SiOCl gas which forms bubbles in the Si02 (oxide) layer being

grown. If this condition should occur, strip the oxide with a “wet clean” and

rerun the High Temperature CI- Cleaning and Oxide Growth with the proper

CI- levels.

After complete drying, insertion of components into furnaces must be done either very slowly (less than 8 inches or 200 mm/minute) or at low temperature (less than 400°C).

Removable ComponentsAfter insertion (see insertion rates below) at any temperature >400°C, hold 1 hour then ramp furnace at a maximum rate of lO°C/minute.

Stationary ComponentsProduct going into a furnace at room temperature (or up to 300°C) should be ramped at a maximum ramp rate of 10°C/minute.

OR: As an alternative, temperature may be raised in 300°C steps with a 20-minute hold at each step.

Appendix D Install in Furnace

Appendix E Surface Preparation

11+1 774 317 2600

Oxidation Time/Temperatures for Non-CVD Coated Components

Temperature: 1100°C 1200°C 1250°C 1300°C

Time-Steam: 24hr 16hr 10hr 6hr

Dry 02: 48hr 30hr 16hr 10hr

Oxidation Time/Temperatures for CVD Coated Components

Temperature: 1100°C 1200°C 1250°C 1300°C

Time-Steam: 10hr 6.5hr 4hr 2.5hr

Dry 02: 19hr 12hr 6.5hr 4hr

1000

1200

1400°C

800

600

400

200°C

1 hour 2 3 4 5 12 13 14 15 16 hours

Dry 02

Steam Only10 Hours

(4 Hours with CVD)

Dry 02Only

6%HCI

3%HCI

10°C/Min

60 Min.

10 Min.

(life is passing)

SOAK AT 1200°C FOR 1 HOURSoak at 1200°C (or maximum achievable temperature) for 1 hour

DISCONTINUE CHLORINE SOURCEDiscontinue CI- source. After 1 hour, the oxide has grown so thick that further penetration/cleaning by the chlorine ions is negligible.

While still at 1200°C (or maximum achievable temperature) allow dry oxygen to purge the furnace for 10 minutes after the CI- ion source has been turned off.

STEAMAfter the 10-minute purge, introduce steam for 16 hours (6.5 hours for CVD SiC coated product). If running at a temperature other than 1200°C, refer to the tables below. Note that CVD SiC coated components only need approximately 40% as much oxidation time.

COOLAfter the steam oxidation, turn off steam, continue oxygen and cool at a rate of 10°C/minute or less.


coorstek.com

©2016 CoorsTek 01753 C

CoorsTek, Inc.+1 303 271 7100+1 855 929 7100 toll free in USA [email protected]

CoorsTek exclusive OpX manufacturing and quality system

Quick-TurnPrototyping and Manufacturing

Note: Information in this bulletin illustrates the general laser services of CoorsTek. Users are responsible for selection of laser services suitable for specific applications. This document, if printed, is not controlled. A controlled copy may be obtained from Quality Assurance. Holders outside of CoorsTek should seek updates on www.coorstek.com. European Union (EU) Directive on Restriction of Hazardous Substances (RoHS): The EU Directive on RoHS specifies that an electronic product or component may not contain a listed substance except as specifically provided in the directive. CoorsTek ceramic substrates meet the requirements of the Directive. Charts intended to illustrate typical properties. Property values vary with method of manufacture, size, and shape of part. Data contained herein is not to be construed as absolute and does not constitute a representation or warranty for which CoorsTek assumes legal responsibility. SuperStrate, Amazing Solutions, and CoorsTek are registered trademarks of CoorsTek, Inc. OpX is a trademark of CoorsTek, Inc.

RTI®

components arrive at the customer location:• Acid cleaned to remove

surface contaminants• C02 cleaned to achieve lowest particle levels• Triple bagged in a Class 10 cleanroom

RTI cleaning can help you:• Eliminate wet cleaning and the

time-consuming drying process• Control costs• Reduce the waste-stream

CUSTOMER CLEAN

Particles (0.3 µm and larger)Method: Dryden QIII Particle Counter 0.6 - 1.5 particles/cm2

CVD Coating ThicknessMethod: Optical Microscopy 110 - 130 µm

PurityMethod: Glow Discharge Mass Spectroscopy

Surface RoughnessMethod: Profilometry Machined/CVD: 1.9 - 2.3 µm As-formed/CVD: 4.1 - 4.9 µm

SiC Coating AdhesionMethod: Scribe/Peel Test–Pass

Method: 1100° C Thermal Shock Test–Pass

Surface Roughness Method: Profilometry Machined/CVD: 2.0 - 2.4 µm As-formed/CVD: 4.4 - 5.0 µm

SiC Coating Adhesion Method: Scribe/Peel Test–Pass

Method: 1100° C Thermal Shock Test–Pass

RTI

Particles (O.3 µm and larger)Method: Dryden QIII Particle Counter < 0.2 particles/cm2

CVD Coating ThicknessMethod: Optical Microscopy 110 - 130 µm

PurityMethod: Glow Discharge Mass Spectroscopy

Fe (ppm)

Al (ppm)

Ca (ppm)

Ni (ppm)

Sample 1 0.02 <0.01 <0.05 0.01

Sample 2 0.02 <0.01 <0.05 0.01

Fe (ppm)

Al (ppm)

Ca (ppm)

Ni (ppm)

Sample 1 0.05 <0.01 <0.05 0.01

Sample 2 0.05 <0.01 <0.05 0.01

Appendix F Ready-to-Install Components

Documents

Cleaning & Surface Preparation Manual