Contact%20Info.

1
Contact Info.

• Name Wing Leong, Chung (Zhong Rongliang, ???)
• Email mfcchung_at_ust.hk
• Tel [phone]
• Rm 2130A

2
Examination

• Time 120 mins
• Open Book
• Passing Marks
• 2 Qualify Question
• Part I 25 mc 60 (Safety)
• Part II 25 mc 60 (Operation)
• Part III 2 PF 60 (Process Flow)
• 5 mistakes / PF

3
NFF Operation Training

• Introduction
• ??

4
Introduction ??

• Contamination and Control ?????
• Process Flow ????
• Dos and Donts ??
• Discussion on Exam Questions ????
• NFF Tour ?????

5
NFF Operation Training

• Contamination and Control
• ?????

6
Research in NFF???????????

• Sub-micron SOI
• Display Technologies
• MEMS
• Integrate Power System
• Advanced Packaging Program
• Advanced Process Module Developing
• Sensor Technology
• Gene Chip
• Compound Semiconductor Technology
• Novel Magnetic electronic devices

• ???SOI
• ????
• ?????
• ??????
• ??????
• ????????
• ?????
• ????
• ????????
• ?????

7
Outline

• Contamination
• Process Verification Scheme
• Cleanliness Levels
• Process Compatibility
• Wafer Status
• General Processing Requirements of Individual
  Modules

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8
What is contamination ????

• Contamination is the intrusion of impurities into
  devices that leads to their failure
• Examples
• Degradation of Oxide Integrity
• Threshold Voltage Shift
• Leakage

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9
Knock-on Effect
Contaminants
Furnace A
Cleaning Bath
Furnace B
Etcher A
Bath for Resist Strip
Tools e.g. Cassette
Bath for Resist Strip
10
Why contamination matters to you????????

• Its like disease, easy to spread across the
  laboratory
• Its hard to be stopped once caused
• Any contamination you cause ruins others years
  of efforts
• You are the only one who can help us stop it from
  spreading

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11
3 Commonest CMOS KillersCMOS??

• Metallic Contaminants
• Ions of heavy and transition metals (Au, Ag, Pt,
  Ni)
• Ions of standard Metal (Al, Ti)
• Alkali Ions (K, Na)
• Orgnaic
• Photoresist and Polymers
• Body Oil
• Particles
• Carbon
• Metal pieces from lifted-off wafers
• You name it

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12
Contamination Control????

• NFF Policy and Rules
• Process Verification Scheme
• Processing Requirements of individual modules
• Your awareness and observance

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13
NFF Policy and Rules?????

• All Users
• General Cleanroom Rules and Regulations
• Non-CMOS Users
• Process Flow
• Satisfactory Completion of Training Courses
• CMOS Users
• Non-CMOS Users requirement
• ELEC508 or Equivalent

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• ????????
• Non-CMOS???
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• ????
• CMOS???
• ??Non-CMOS??????
• ??ELEC508?????

14
Process Verification Scheme ??????

• Every thing in NFF
• Chemicals
• Materials
• Wafers
• Equipment and Machines
• Classified by
• Contamination Risks
• Process Compatibility
• 7 equipment Combination
• 4 Wafer Statuses

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• 7??????
• 4???????

15
Whats Risk
Low Risk
Si Wafer
Al
Al

ltlt
Na

Au
Au

ltlt
High Risk
16
Contamination Risks and 3 Cleanliness
Levels???????????

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• ????
• ??? (????)
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• ??? (????)
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• Clean (Lowest)
• No contaminants
• Semi-Clean (Medium)
• Ions of standard materials such as Al, Cr, and Ti
• Non-Standard (Highest)
• Ions of gold, copper, GaAs, Ga Nitride, K, Na and
  materials/chemicals not yet classified

17
Process Compatibility?????

• CMOS Compatible
• Front End Processes of ELEC508, PMOS, NMOS, and
  SOI
• Non-CMOS Compatible
• MEMS
• CMOS back-end process
• You Name it

• CMOS??
• ELEC508?PMOS?NMOS?SOI????
• ?CMOS??
• ?????
• CMOS????
• ????

18
3 Cleanliness 2 Compatibilities 4 Wafer
Statuses ?????? ??????? 4???????
7 Combinations 7???
Clean ??
Semi-Clean ???
Non-Standard ???
Clean CMOS
CMOS
Both ??
Clean CMOS/Non-CMOS
Clean/Semi-clean CMOS/Non-CMOS
Clean Non-CMOS
Semi-clean Non-CMOS
Non-Standard Non-CMOS
Non-CMOS
Semi-clean/Non-Standard Non-CMOS
19
Mechanism of PV Scheme?????????

• Downward Compatible
• CMOS -gt Non-CMOS
• Clean -gt Semi-clean or Non-standard
• Semi-clean -gt Non-standard
• But not the Reverse
• Non-standard -gt Semi-clean -gt Clean
• Once contaminated always contaminated
• Exceptions
• Decontaminated MILC Wafers
• Decontaminated wafers after Post CMP Grinding
  Cleaning

• ????
• CMOS -gt Non-CMOS
• ??-gt ???????
• ???-gt ???
• ????
• ??? -gt ???-gt ??
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20
Decontamination????

• Wafer Status after decontamination
• Clean Non-CMOS
• Not for
• Non-standard Wafers
• Almost all Semi-Clean Wafers
• Not necessary for Non-CMOS users

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• ?? NON-CMOS
• ???
• ?????
• ????????
• NON-CMOS???????????

21
Processing Requirements of individual
processes???????????

• Wetstations
• Oxidation, Diffusion and CVD
• Implantation
• Dry Etching
• Sputtering
• Photolithography

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22
Wetstations ?????

• General Safety
• No chemicals bottle left on the floor
• Wafers have to be dump-rinsed in the dump-rinser
  for at least 4 cycles immediately after any
  chemical processes
• No organic solvent (IPA, Acetone)
• HF
• Highly hazardous Chemical Solutions (HF, BOE, 777
  and Freckle etch)
• Concentration below 20 is more insidious and
  symptoms may be delayed for up to 24 hours
• Use of Chemical
• Unconventional use of chemical requires
  permission and booking.
• Mixing own chemicals is only allowed at
  semi-clean or non-standard wetstation

• Disposal
• HF, Freckle Etch and BOE are needed to be drained
  into the HF tank by NFF staff.
• Acid and Base are needed to be drained by users
  themselves with an aspirator
• Contamination
• No Glass, Metals and Manual coated wafers at
  CLEAN wetstations
• No Metals at the sulfuric acid bath for resist
  stripping
• Separation of cassettes, tools containers and
  gloves from those of different stations
• No lifted-off wafers put in baths
• No mess left at wetstations

23
Layout of Wetstations??????
24
Labels of Wet-stations??????????
Lowest
ACMOS Cleaning Station
BNon-CMOS Cleaning Station
COxide and nitride etch
GTMAH Etching Station
ESemi-clean Non-metal Processing Station
Risks of Contamination
DStandard metal processing Station
YSemi-clean Organic Stripper
ZSemi-clean Develop Station
Z2Semi-clean/Non-standard Dump Rinser
FNon-standard Processing Station
JASTRIs Station (for ASTRI only)
Highest
25
Summary of Wetstation Arrangement??????
26
Oxidation, Diffusion and CVD ????????????

• Wafer Substrates
• Thickness
• Full Wafers Preferred
• Appropriate Cleaning Processes
• No Photoresist
• No organic
• No metals for most furnaces
• No wafers of uncertain background

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27
Implantation????

• Full wafers without chips and cracks
• Spices (B, BF2, As, P, H)
• Dosage
• High Temperature Photoresist
• Wafers with no resist on the rim and back side

28
Dry Etching ????

• Materials to etch (Oxide, Nitride, Si, Poly, some
  metal, compound Semiconductor)
• Thickness to etch
• Full Wafers Preferred
• Single Side Photoresist Coating
• No wafers with edges wrapped with photoresist.

29
Sputtering ??

• ???????????
• ???????5000A
• ??????

• Limited Target Materials
• Thickness lt 5000A
• Full Wafers Preferred
• No photoresist nor broken wafers on Semi-clean
  Sputterers
• Lift-off wafer in Non-Std sputterers only

30
Photolithography??

• Contamination caused by photoresist
• Inhalation of Organic Vapors and Solvent (HMDS,
  Photoresist)
• No acid nor base in Yellow Room
• Coater and developer Tracks not for double-side
  photoresist coating, and negative photoresist

• Disposal of Waste (IPA, Acetone)
• Pour the waste into waste collection bottles
• Dont use an aspirator to suck it into the N-tank
• Be careful of EKC, which is a highly corrosive
  solvent
• Containers used for developing or any process
  require booking on the computer system.
• Transparency only allow on AB-M 2

31
Contamination arising from Integration

• Inter-level Contamination
• Caused by contaminants from incompatible
  cleanliness groups
• E.g. Non-standard group contaminates Semi-clean
  group
• Intra-level Contamination
• Caused by contaminants from the same cleanliness
  level
• Heavily Doped Photoresist/PSG Vs some CLEAN
  equipment
• Cr/Al/ITO vs Some SEMI-CLEAN equipment
• PCB boards vs Non-Standard Sputterers
• Extra-level Contamination
• Caused by contamination sources other than the
  above
• E.g. Photoresist, Particles, Body Oils, to name
  but a few

32
NFF Operation Training

• Process Flow
• ????

33
Outline

• Aim
• Standard Format
• Common Mistakes
• Process Guidelines

34
Aim of Process Flows

• Functions
• Help you to plan ahead
• Track down wafer movement
• Reduce uncertainty
• keep the unqualified away from NFF
• Aim
• Control Contamination

35
Sample Process Flow



36
Standard Format

• Heading
• Cross-sections
• Wafer Status
• Step no.
• Equipment
• Cleanliness
• Compatibility
• Processes
• Requirements

37
Mistake 1 - Oversimplification
38
Mistake 2 Wrong Initial Wafer Status
39
Mistake 3 Incompatible equipment Status
40
Mistake 4 - Double-side PR Coating
41
Mistake 5 Wrong PR Stripping
42
Other Mistakes

• Mistake 6 - Misuse of low stress nitride as
  oxidation masks
• Mistake 7 Misuse of Decontamination
• Mistake 8 Wafer Edge Coating
• Mistake 9 missing backside rinsing prior to
  implantation

43
Process Guidelines

• 7 Cleanings
• 4 Resist Stripping
• Post-Deep Si Etch Polymer Removal

• 3 Etchings to Etch Through Wafers
• Liftoff
• Non-standard Metal (Gold)

44
Cleanings

• Sulfuric Clean (CMOS)
• RCA2(Decontamination)
• Pre-diffusion Clean (CMOS)
• Pre-deposition Clean (CMOS)
• Sulfuric Clean (Non-CMOS)
• Post-Metallization Clean
• Mask Cleaning

45
Sulfuric Clean (CMOS)

• CMOS Only
• No photoresist, metals nor silicides
• A1H2SO4H2O2 A2HFH2O 150
• Removing organics and gross contaminants e.g.
  scribe dust.
• H2SO4 reduces organics to carbon
• H2O2 oxidizes carbon to form CO2

46
RCA2(Decontamination)

• CLEAN or Decontaminatable Wafers
• No photoresist, metals
• B3H2OH2O2HCl at 70 ºC (fresh)
• Drain after use
• Removes metallic contaminants and alkali ions
• HCl reacts with most metals to form soluble
  chlorides
• H2O2 acts as a buffer/oxidant

47
Pre-diffusion Clean (CMOS)

• CMOS Only
• No photoresist, metals nor silicides
• Process
• A3H2SO4H2O2 cleans organics
• Dump rinse
• A2HFH2O (150)
• Dump rinse
• Spin Dry
• Prior to the growth of high quality oxide

48
Pre-deposition clean (CMOS)

• CMOS only
• No photoresist, metals nor silicides
• Process
• A1Sulfuric Clean
• Dump rinse
• A2HFH2O (150) cleans native oxide
• Prior to deposition

49
Sulfuric Clean (Non-CMOS)

• Clean MEMS only
• No photoresist, metals nor silicides
• B1H2SO4H2O2 B2HFH2O 150
• Removing organics and gross contaminants e.g.
  scribe dust.
• H2SO4 reduces organics to carbon
• H2O2 oxidizes carbon to form CO2

50
Post-Metal Clean

• Semi-clean
• No non-standard materials esp. Gold, nor samples
  undergone liftoff
• Process
• - Clean wafers with Fresh MS2001 in Bath Y2
  (Optional)
• Spin wafers Dry with Spin-dryer D

51
Mask Cleaning

• Semi-Clean
• Mask Only
• Process
• Y2MS2001
• Dump-rinse
• Dry by an N2 Gun
• Oven

52
Resist Strips

• Sulfuric Acid (E4)
• CLEAN
• SEMI-CLEAN Without Metals/ Silicides
• MS2001 (Y1)
• Standard Metals
• Semi-Clean
• O2 Ashers Wet (E4, Y1)
• High-temp Treated PR
• Non-Standard W2
• Non-Standard

53
Resist Strip (General)

• Semi-Clean and Clean
• No metal nor silicide, nor ITO, nor heavily
  doped/implanted photoresist, nor undensified
  doped LTO
• Process
• E4Sulfuric Acid
• Dump-rinse
• Inspection

54
Resist Strip (post implatation or high temp
treatment)

• Semi-Clean and Clean
• No metal nor silicides
• Process
• O2 Plasma ashing
• E4Sulfuric Acid/Y1MS2001(it depends)
• Dump-rinse
• Inspection

55
Resist Strip (Standard Metals)

• Standard Metals
• No samples undergone liftoff
• Process
• Y1MS2001
• Dump-rinse
• Spin Dry
• Inspection

56
Resist Strip (Non Standard)

• Standard Metals
• No samples undergone liftoff
• Process
• W2MS2001
• Dump-rinse
• Spin Dry
• Inspection

57
Post ICP Deep Silicon Etch Polymer Removal

• Clean CMOS/Non-CMOS
• Wetstation X
• Process
• EKC265 Stripper
• 70 C
• 20 mins
• Inspection

58
Etching Through Wafers

• Dry Etch
• Deep-silicon Etcher
• Under Installation
• KOH
• Etching furiously
• Non-standard Process
• TMAH
• CLEAN Process
• Nitride Oxide as Etching Masks

59
ICP Deep Silicon Etcher
Method 1
Method 2
8 um thick Photoresist
Scratches
Oxide
Sub-
strate
Substrate
Particles generated from here
Note The manual photoresist developing or
polymer removal must be done at Wetstation X
60
KOH Etching Non-standard
Nitride
Oxide
What if resist is scratched away?
Ideal
Photoresist
Particles Generated From here
Scratches
61
TMAH Etching
Nitride
Oxide
Photoresist
Particles Generated From here
Scratches
Ideal
Substrate
What if resist is scratched away?
Substrate
62
Particulate - liftoff
Photoresist
Step 1
Metal
Step 2
Photoresist
Metal Residue
Step 3
Photoresist Residue
63
Particulate liftoff (cont)

• Guideline for liftoff process
• Acetone, and IPA used should be poured into
  dedicated waste bottles
• Make it the last step
• Once liftoff is done, the samples cant stop
  generating contaminants.
• Dont even think about putting samples into any
  processing baths, That is extremely irresponsible!

64
Metallic Contaminant Gold

• Gold Ions
• Most-Contaminating because of its high mobility
• Easy to spread into the atmosphere, if heated
• From films, equipment, tools, containers and
  cassettes, which are in contact with Au ions
• Totally incompatible with almost all processes
  and equipment except for
• Bath Z2
• Wetstation F
• Thermco E4 Thermal Anneal (Gold)

65
Metallic Contaminant Gold

• Guidelines for processing gold
• Make it as close to the last step as possible.
  Once samples are gold-contaminated, you are
  banned from doing almost all processes.
• Never put gold-contaminated samples into clean
  and semi-clean areas, (in particular sulfuric
  acid for resist stripping). Otherwise you will
  kill the whole laboratory!

66
NFF Operation Training

• Dos and Donts
• ??

67
Chemicals and Wetstations

• Dont bring your own chemicals or materials into
  NFF unless you have approval
• Dont take any chemicals or materials away. That
  is theft.
• Dont leave chemical bottles on the floor
• Never put into CLEAN baths wafers that have
  undergone metallization.
• Dont leave anything, especially incompatible
  materials, on the top of wet-stations.
• Disposal of HF and BOE must be done by trained
  persons

• Dont be so irresponsible as to leave down the
  tools you have used and go away
• Dont mix up the gloves, cassettes and tools of
  one station with those of others. You should look
  at the labels!
• Clean all the tools and containers you have used
  and place them back to where they are
• No ORGANIC Solvent at wetstations in Class 1000
• No acid and base in Yellow Room

68
Operation

• Store wafers of different wafer status in
  separate boxes
• Always inspect your wafers after a resist strip
  to ensure cleanliness
• Dont put non-standard materials, especially gold
  into semi-clean and clean baths
• Dont put liftoff samples in any processing baths

• Always keep your samples in your own containers
  or cassette boxes in case they contaminate others
  or be contaminated.
• Always be careful with photoresist which is very
  contaminating.
• Arrange non-standard steps as close to the end of
  process flow as possible.
• After cleaning, wafers must go straight to
  furnaces without being touched by any objects

69
Process Flows

• Plan before work. If you fail to plan you are
  planning to fail
• Write what you do and do what you write.
• Once your process becomes different from what you
  have planed, sumit us a new flow

• Never copy others process flow
• Never let others copy your process flow
• Do let us know, if you find your processes
  departing from our scheme.
• Proofread before submitting them

70
Personal

• Dont shortcut any policy and rules
• Keep yourself abreast of information about rules
  and regulations, as it is dynamic and subject to
  change.
• Report to us any mistakes you or others have
  made. Dont hide it!
• be aware of contamination that you may cause and
  others cause

• Remember, this is a shared lab. Everyone must
  follow lab policy to keep it clean
• Use your judgment. Avoid contamination of wafers
  or equipment
• Dont stay in the laboratory if not necessary.
  NFF is not a meeting place!

71
Useful Webpages

• NFF User Guide (well underway)
• Hook up to http//www.nff.ust.hk and then click
  on Safety course registration or
• http//www.nff.ust.hk/mffdoc/index.htm
• NFF Booking System
• https//www.nff.ust.hk/booking
• Material Request Form
• Logon NFF Booking System and then click on
• User Info
• Other process information
• http//mfk060.ust.hk

72
NFF Operation Training

• QA
• ????