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Micro/Nanosystems TechnologyWagner / Meyners 1
Micro/Nanosystems Technology
Prof. Dr. Bernhard Wagner
Dr. Dirk Meyners
Micro/Nanosystems TechnologyWagner / Meyners 2
Micro/Nanosystems Technology
Outline
• Cleanroom and vacuum technology
• Cleanroom technology
• Working in a cleanroom
• Kiel’s Nanolab
• Vacuum technology
Micro/Nanosystems TechnologyWagner / Meyners 3
Micro/Nanosystems Technology
Outline
• Cleanroom and vacuum technology
• Cleanroom technology
• Working in a cleanroom
• Kiel’s Nanolab
• Vacuum technology
Micro/Nanosystems TechnologyWagner / Meyners 4
Working in a cleanroom
Sources of contamination
form of
contamination
source resulting problem
dust humans, incoming
air, abrasion
shadowing during
lithography
molecular oil, remains of
resist
bad adhesion
ionic contact with skin,
water
electrical
interference
atomic etching electrical
interference
Wrong behavior in a cleanroom can degrade cleanliness by two classes.
Humans are the most important contamination source.
Special behavioral rules
Micro/Nanosystems TechnologyWagner / Meyners 5
Working in a cleanroom
Cleanroom clothes
one-piece coat, shoes, gloves
and cap
Kiel’s Nanolab
special hoods to provide
sterility
Pharmaceutical fabricationMedium standard
mask,
overboots
Micro/Nanosystems TechnologyWagner / Meyners 6
Working in a cleanroom
Particle emission during activities
activity emission of particles with diameter > 0.5µm
min-1
street clothes one-piece coat,
shoes, gloves,
cap, mask
sitting without
movement
0.3 x 106 0.7 x 104
moving head 0.6 x 106 1 x 104
moving body 1 x 106 3 x 104
going slowly 3 x 106 5 x 104
going fast 6 x 106 10 x 104
values according to: R. Zengerle, lecture notes, Mikrosystemtechnik, IMTEK
move slowly, do not rush
Micro/Nanosystems TechnologyWagner / Meyners 7
Working in a cleanroom
Behavioral rules:
- wear cleanroom clothes
- no cosmetics, especially no powders
- avoid skin contact to substrates, chemicals and machines (wear
gloves)
- speaking only with head turned away from substrates
- use wafer boxes for transport and storage of wafers
- do not use pencils, use special paper appropriate for cleanrooms
- do not break silicon wafers into pieces
- do not smoke immediately before entering
Micro/Nanosystems TechnologyWagner / Meyners 8
Micro/Nanosystems Technology
Outline
• Cleanroom and vacuum technology
• Cleanroom technology
• Working in a cleanroom
• Kiel’s Nanolab
• Vacuum technology
Micro/Nanosystems TechnologyWagner / Meyners 9
Kiel’s Nanolab
Filter Fan Unit
Process
equipment
Gas exhaust
additional air
gray area white area gray area
Micro/Nanosystems TechnologyWagner / Meyners 10
Kiel’s Nanolab
Gray Area
White Area
Transmission Electron Microscope
(TEM)
Magnetically
Shielded
Room
lab lab lab
neutralization
P white > P gray > P outside
air
lock
air
lock
(machines)
Micro/Nanosystems TechnologyWagner / Meyners 11
Kiel’s Nanolab
Gray Area
White Area
Transmission Electron Microscope
(TEM)
lab lab lab
neutralization
P white > P gray > P outside ΔP = 10Pa
Magnetically
Shielded
Room
Micro/Nanosystems TechnologyWagner / Meyners 12
Kiel’s Nanolab
The lower the particle density the higher the air exchange:
cleanroom class
(209 D)
air flow
[m3/hm2]
air exchange
[number/h]
100 000 60 20
10 000 60 – 120 20 - 40
1 000 700 – 1 100 200 - 300
100 1 600 – 1 800 500 - 600
approximate values according to: R. Zengerle, lecture notes, Mikrosystemtechnik
cleanroom area: 300 m²
technical/utility area: 600 m²
white area: class 100
gray area: class 1000
white area: ca. 150 m²
1800 m³/hm² * 150 m² = 270 000 m³
air conditioning: 20 000 m³/h
air circulation
Micro/Nanosystems TechnologyWagner / Meyners 13
Kiel’s Nanolab
• additional air
• temperature control: 22°C +/- 2°C
• air humidity control: 45% +/- 10%
• neutralization of sewage water
• cooling water
• central gas supply
• compressed air
• electric power
Detailed description is
part of the first lab course
Micro/Nanosystems TechnologyWagner / Meyners 14
Kiel’s Nanolab
Gray Area
White Area
Transmission Electron Microscope
(TEM)
2
1
3
1
15
8
9
7
6
1013
13
13
12
11
22
19
20
17
1618
14
15
2
1
4
Airlock
Wet Chemistry
1 Workbenches
2 Electroplating
3 Dicing Saw
4 Magnetron Sputtering
System 6 Inch
5 PVD-Devices
6 Rapid Thermal
Annealing (RTA)
7 Ion Beam Etching (IBE)
8 Inductively Coupled
Plasma (ICP) Etching /
Reactive Ion Etching
(RIE)
9 Plasma Enhanced
Chemical Vapour
Deposition (PECVD)
Thin Film technique 1
10 Magnetron Sputtering
System 4 Inch
11 Pulsed Laser Deposition
12 Evaporative Deposition
13 CVD-Devices
Lithography
14 Optical Microscope
15 Profilometer
16 Mask Aligner 6 Inch
17 Mask Aligner 4 Inch
18 Workbench
19 Spin Coater
20 Oven
21 Scanning Electron
Microscope (SEM) /
Focused Ion Beam
22 Ellipsometer
Thin Film technique 2
Micro/Nanosystems TechnologyWagner / Meyners 15
Wet Chemistry
• Wet Chemistry for Etching, Cleaning and Drying
– Quick dump rinse
– Fine rinse basin with conductivity measurement
– Spin dryer for single wafer
– 3 Ultrasonic bathes
– Fume hood for hydrofluoric acid (HF)
Workbenches
Micro/Nanosystems TechnologyWagner / Meyners 16
Wet Chemistry
Electroplating
• Electroplating
– 2 basins for electroplating
(Au and Cu)
– Bath for cleaning
Micro/Nanosystems TechnologyWagner / Meyners 17
Wet Chemistry
Dicing Saw
Automatic Dicing Saw DAD 3350 provided by DISCO
Specifications
• Up to 8“ substrates can be diced.
• Substrate may be made of a variety of materials
such silicon, quartz, borosilicate glass, …
• Max. cutting speed amounts 600 mm/s
• High resolution at both X-, Y-, Z-axis
• Water cooling of spindel and substrate
• Graphical user interface
A special feature:
• Our device can perform round cuts to obtain
for example a 4 inch wafer
from a 8 inch wafer.
Micro/Nanosystems TechnologyWagner / Meyners 18
Thin Film technique 1
Sputter Deposition: Von Ardenne CS 730 S
• Cluster deposition system with 3 chambers and 9 sputter sources
• 8“ and 4“ targets
• Load-lock with 10 x 6“ substrate plate magazine
• RF and DC sputtering up to 3 kW
• 6“ Substrates, radiative heating possible
• Sputter gases: Ar, N2, O2
• Magnetic bias field (100 Oe) possible
• RF etching
Current target list:
• Metals: Ag, Au, Cu, Al, Cr, Ru, Ta, Ti, Mo
• Alloys: FeCo, FeCoBSi, TbFe, NiTi, NiFe, CoFeB, FeAl,
FeB, FeHf, FePd, MnIr, TiNiCu
• Oxides, Nitrides: Al2O3, MgO, Ni3N8, ZnO2, AlN
(other oxides by reactive sputtering)
Micro/Nanosystems TechnologyWagner / Meyners 19
Thin Film technique 2
Magnetron Sputtering device (ALCATEL 450)
• Power supply:
– RF ( 600W)
– DC ( 600W)
• Final Vacuum: 1E-7mbar
• Gas: Ar 6.0 and O2
• Cathodes (3 x 100mm in Ø)
• Substrates:
– Planar
– Tubular
• Heater (up to 600°C)
• Adjustable distance between
substrate and cathode
Micro/Nanosystems TechnologyWagner / Meyners 20
Thin Film technique 2
High Vacuum Evaporating-System PLS 500
• System: Electron-beam evaporator
• Substrate: Dimension: up to 100mm
Substrate heater up to 600°C
• Film-thickness monitoring with oscillating quartz
Micro/Nanosystems TechnologyWagner / Meyners 21
Thin Film technique 1
• PECVD-Tool from Sentech (SI500-PPD)
– SiH4/NH3/NO2 based chemistry to deposite silicon, silicon
oxide, silicon nitride and oxinitrides
• Used for:
– Passivation and insulating
layers for sensors
– Highly selective hard masks
for deep etching
– Dielectric layers for capacitors
– Guiding layer in surface
accoustic waves devices
Plasma enhanced deposition
Micro/Nanosystems TechnologyWagner / Meyners 22
Thin Film technique 2
Pulsed Laser Deposition Workstation
Specifications
• 1“ substrate holder, heatable up to 1000 °C in oxygen
• Coherent Compex Pro 201 excimer Laser
• 4 x 2“ target assembly
• RHEED (reflection high energy electron diffraction)
• Film thickness homogenity over 1“ = ± 5 %
Advantages of the method:
• Stochiometric transfer from multi-element targets (eg.
YBa2Cu3O7)
• Very good thickness control through number of pulses
• Deposition of high quality thin films of different materials
and control of crystallographic structure by RHEED
Micro/Nanosystems TechnologyWagner / Meyners 23
Lithography
Spin Coater
• Spin Coater OPTIspin ST22P
– Substrate size up to 8“
– Chucks for 4“, 6“, 8“ and
pieces
– spin speed up to 10,000 rpm
• Hot Plate
– HMDS Adhesion promoter
(C6H19NSi2)
– Temperature up to 200°
Micro/Nanosystems TechnologyWagner / Meyners 24
Lithography
Mask Aligner
– Substrate size: 6“-wafer or 6“ x 6“
– Mask size 7“ x 7“ (e.g. glas wafer with Cr patterns)
– Exposure source 350W Hg lamp
– UV wavelength range 350 – 450 nm
– Resolution down to 0.4 µm
– Top/bottom side alignment
– Modes:
• Vacuum Contact
• Hard Contact
• Soft Contact
• Proximity
(gap 1 – 300µm)
• Mask Aligner Süss Microtec MA6 for UV Lithography
UV
lamp
mask
photoresist
substrate
Micro/Nanosystems TechnologyWagner / Meyners 25
Lithography
UV Lithography – (Suss Mask align 4”)
• 200W Hg lamp
• UV light wave length: 365nm
• Light intensity : 28mW/cm2
• Exposure uniformity: ± 1,3%
• Sample :
– ≤ 4” wafer (planar)
– From 0,5 to 5 mm
diameter tubes (100 mm
length)
• Cr mask: 5”
Micro/Nanosystems TechnologyWagner / Meyners 26
• SEM:
– resolution: 0.9nm (1.4nm) @ 15kV (1kV)
– secondary and back scattered electron detection:
– large chamber for inspection of 4’’ (6’’) wafers
• FIB:
– Gallium Ion emitter
– resolution: 5nm @ 30kV
• GIS:
– Platinum and Insulator (SiOx) deposition
– Insulator and Metal Etching
• E-beam-lithography
– pattern size <50nm
• EDX:
– LN2 free Detector (Oxford)
– energy resolution: 129 eV (Mn K)
Lithography
FEI Dualbeam Helios Nanolab
Micro/Nanosystems TechnologyWagner / Meyners 27
Thin Film technique 1
Ion Beam Etching
Ionfab 300 Plus provided by Oxford Technologies
Specifications
• Up to 6“ substrates can be processed.
• A wide variety of materials can be
etched: Metals, oxides, semiconductors, …
• Etch uniformity over 6‘‘ at least
as high as 3%
• End point detection available
• He backside cooling
Advantages of the method:
• Flexibility: since probe material is
„merely“ milled, any layer or multilayer
system can be patterned.
• Reliability: the SIMS (Scanning Ion Mass Spectrometry)
feature allows for an exact monitoring of the etch process
and for the detection of process end point.
Micro/Nanosystems TechnologyWagner / Meyners 28
Thin Film technique 1
Inductively Coupled Plasma etching: Bosch process
• ICP-RIE-Tool from Sentech (SI500)
– SF6 based plasma chemistry step to etch into silicon
– Alternating plasma with C4F8 deposition passivate the sidewall
• Used for:
• Deep etching of silicon structures
Micro/Nanosystems TechnologyWagner / Meyners 29
Optical Microscope
• Optical Microscope Nikon
Eclipse L200
– magnification up to 1000x
– objectives: 5x, 10x, 20x,
50x, 100x
– 8 x 8 stage with 4“-6“
wafer holder
– filter for photo resists
– bright field/dark field
– polarizer and analyzer
Lithography
Micro/Nanosystems TechnologyWagner / Meyners 30
Lithography
Profilometer
• Ambios XP-2
– Stylus radius 2µm
– Stylus force 0.05mg – 10mg
– Motorized X-Y-Stage, 6“
– Manual 360° rotation
– Vacuum chuck
– 40x-160x color camera
Micro/Nanosystems TechnologyWagner / Meyners 31
Micro/Nanosystems Technology
Outline
• Cleanroom and vacuum technology
• Cleanroom technology
• Working in a cleanroom
• Kiel’s Nanolab
• Vacuum technology
Micro/Nanosystems TechnologyWagner / Meyners 32
Vacuum technologyA definition of vacuum:
• Theoretically: a space without matter
• Practically: a chamber in which the pressure is far below the normal
atmospheric pressure. Processes carried out in this chamber are not
effected by the remaining gas.
Vacuum technology is the entirety of systems and processes applied
for reducing pressure in cavities.
classification of pressure ranges
class pressure [mbar]
low vacuum (Grobvakuum) 103 – 100
fine vacuum 100 – 10-3
high vacuum 10-3 – 10-7
ultra high vacuum < 10-7
Micro/Nanosystems TechnologyWagner / Meyners 33
Vacuum technology
A
FP
Pressure P is the force F per unit area applied to an object in a
direction perpendicular to the surface.
Pressure Units
pascal bar technical
atmosphere
physical
atmosphere
torr pounds per
square inch
1 Pa 1 N/m² 10-5 1.0197x10-5 9.8692x10-6 7.501x10-3 145.04x10-6
1 bar 105 1 1.0197 0.98692 750.06 14.504
1 at 98 067 0.98067 1 0.96784 735.56 14.223
1 atm 101 325 1.01325 1.0332 1 760 14.696
1 torr 133.32 1.333x10-3 1.3595x10-3 1.3158x10-3 1 19.337x10-3
1 psi 6 894.8 68.95x10-3 70.307x10-3 68.046x10-3 51.715 1
Micro/Nanosystems TechnologyWagner / Meyners 34
Vacuum technology
Basic assumptions:
• A number N of atomic particles with mass ma is uniformly distributed in
volume V.
• The particle agitation is disordered.
• Each particle moves with its own velocity v.
momentum:
kinetic energy:
vmp a
2
2
1vmE akin
Micro/Nanosystems TechnologyWagner / Meyners 35
Vacuum technology
The ideal gas law combines the quantities Pressure P, volume V and
temperature T:
In vacuum science the ideal gas low is an accurate approximation since
particle densities are low.
Standard reference conditions:
1-23
23-
mol6.02x10 constant Avogadro :
K)J/(mol 8.31 constant gas :
/1.38x10 constant Boltzmann:
with,
a
a
N
R
KJk
N
NnnRTkTNPV
Tn = 273.15 K = 0°C
Pn = 1.013 bar = 760 Torr
Micro/Nanosystems TechnologyWagner / Meyners 36
Vacuum technology
The velocity distribution of ideal gas particles is given by the
Maxwellian function F(v):
kT
mv
evkT
mvF
dv
dN
N22
2
32
42
)(1
velocity
particle
number
temperature
Micro/Nanosystems TechnologyWagner / Meyners 37
Vacuum technologyThe average path a particle moves without collision with another particle is
called the mean free path. In MST many processes (e.g. deposition processes)
demand large values of the mean free path in the range of chamber dimensions.
• Particles behave like firm balls with radius r∞.
• A collision happens if the center of a second particle enters the cross section
of particle 12
R
Image source: W. Menz,
Mikrosystemtechnik für
Ingenieure, 2005
Micro/Nanosystems TechnologyWagner / Meyners 38
Vacuum technology
On its path particle 1 will hit all the particles contained in the volume lV
Number of collisions:
Mean free path:
The mean free path increases with decreasing particle density ρ and
cross section.
lVN
1
N
l
l
Micro/Nanosystems TechnologyWagner / Meyners 39
Vacuum technology
Mean free path of molecules [m]
pressure [mbar] air hydrogen
1000 60 x 10-9 200 x 10-9
1 60 x 10-6 200 x 10-6
10-3 6 x 10-2 20 x 10-2
10-6 60 200
10-9 60 x 103 200 x 103
values according to: W. Menz, Mikrosystemtechnik für Ingenieure, 2005
Micro/Nanosystems TechnologyWagner / Meyners 40
Vacuum technology
Adsorbtion and Desorbtion
If gas atoms collide on a surface, then they remain there with a particluar
probability, i.e. they are adsorbed. The process of liberation of atoms off the
surface is in competition with that and is called desorbtion.
Monolayer
The surface plane is covered as densely as possible with adsorbed gas atoms
adjacent to one another.
Lower coverage
At lower coverage n one
refers to a partial coverage:
Image source: R. Zengerle, lecture notes, Mikrosystemtechnik
monon
n
Micro/Nanosystems TechnologyWagner / Meyners 41
Vacuum technology
Monolayer formation time (monotime):
• The time necessary in order to cover an initially free surface with a
monolayer:
• Particle flux j depends on gas pressure and temperature. From the ideal gas
law and the Maxwellian function one can derive:
• For nitrogen at room temperatur:
jnt monomono /
RTMNP
nt molar
a
monomono 2
][; 106.3 6
mbarPP
stmono
(assuming a sticking coefficient S = 1)
Micro/Nanosystems TechnologyWagner / Meyners 42
Vacuum technology
Nitrogen at room temperature
pressure
[mbar]
1 10-3 10-7 10-11
tmono [s] 3.6 x 10-6 3.6 x 10-3 36 100 h
Monolayer formation time:
Sticking coefficient S = rate of adsorbtion / rate of impingement
• strongly material dependent (surface and gas)
• strongly dependent on partial coverage
• e.g.: S = 0.1 … 10-3 for Nitrogen on Si (111) *
* R. E. Schlier, H. E. Farmsworth, Structure and Adsorption Characteristics of Clean Surfaces of
Germanium and Silicon, J. Chem. Phys. 30(4), 917, 1959.
Micro/Nanosystems TechnologyWagner / Meyners 43
Vacuum technology
Summary:
pressure range pressure mean free path monotime
low vacuum
fine vacuum
high vacuum
ultra high vacuum
b: chamber dimension