11

Contact Info.Contact Info.

• Name: Wing Leong, Chung (Zhong Rongliang, 锺荣亮 )

• Email: mfcchung@ust.hk• Tel: 2358 7211• Rm: 2130A

• Name: Wing Leong, Chung (Zhong Rongliang, 锺荣亮 )

• Email: mfcchung@ust.hk• Tel: 2358 7211• Rm: 2130A

22

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

NFF Operation TrainingNFF Operation Training

Introduction 概引

Introduction 概引

44

Introduction 概引

• Contamination and Control 污染與管制

• Process Flow 工藝流程• Do’s and Don’t’s 規矩• Discussion on Exam Questions 考題

討論• NFF Tour 參觀實驗所

NFF Operation TrainingNFF Operation Training

Contamination and Control 污染與管制

Contamination and Control 污染與管制

66

Research in NFF微電子實驗所的科研項目

• 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

• 亞微米 SOI• 顯示技術• 微機電系統• 集成功率系統• 先進封裝程序• 先進工藝模塊發展• 傳感器技術• 基因晶片• 化合物半導體技術• 新微電器件

77

Outline

• Contamination• Process Verification

Scheme• Cleanliness Levels• Process

Compatibility• Wafer Status

• General Processing Requirements of Individual Modules

• 污染

• 工藝驗証指引• 潔淨級別• 工藝兼容性• 晶片潔淨指數

• 個別模組的要求

88

What is contamination 何謂污染

• Contamination is the intrusion of impurities into devices that leads to their failure

• Examples:• Degradation of Oxide

Integrity• Threshold Voltage

Shift• Leakage

• 污染：器件因雜質而導致功能失效

• 例如：• 氧化層失效

• 國值電壓漂移

• 漏電

99

Knock-on Effect

Bath for Resist Strip

Contaminants

CleaningBath

Tools e.g.Cassette

Furnace A

Furnace B

Etcher A

Bath for Resist Strip

1010

Why contamination matters to you?

污染與我可干？• It’s like disease, easy

to spread across the laboratory

• It’s 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

• 有如瘟疫一般，易於傳播到實驗的每個角落

• 一旦發生，難以制止

• 因你做成的污染，可把別人多的努力毀於一旦

• 可以幫助我們阻止污染傳播開去的，只有你！

1111

3 Commonest CMOS KillersCMOS 三煞

• Metallic Contaminants• Ions of heavy and transition m

etals (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 wa

fers• You name it

• 金屬污染物• 重金屬和過渡金屬 ( 金、

銀、白金、鎳 ) 的離子• 常規金屬的離子 ( 鋁、鈦 )• 鹼性離子 ( 鉀、鈉 )

• 有機污染物• 光刻膠和聚合物• 體液

• 微粒• 炭• 剝離了的金屬碎片• 不能盡錄

1212

Contamination Control污染管制

• NFF Policy and Rules

• Process Verification Scheme

• Processing Requirements of individual modules

• Your awareness and observance

• 政策與規則• 工藝驗証指引

• 個別模組要求的工藝規格

• 你對污染的關注與規則的尊從

1313

NFF Policy and Rules政策與規則

• 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

• 所有實驗所的使用者• 一般無塵房的規則

• Non-CMOS 使用者• 工藝流程• 訓練合格

• CMOS 使用者• 符合 Non-CMOS 使用者的

要求• 完成 ELEC508 或同等經驗

1414

Process Verification Scheme 工藝驗証指引

• Every thing in NFF• Chemicals• Materials• Wafers• Equipment and

Machines

• Classified by• Contamination Risks• Process Compatibility

• 7 equipment Combination

• 4 Wafer Statuses

• 所有在實驗內的東西• 藥品• 物料• 晶片• 機台

• 按以下因素分類• 污染風險• 工藝兼容性

• 7 種機台的組合• 4個晶片潔淨指數

1515

What’s Risk

+Al

+Na

Al

Si Wafer

Au

Low Risk

High Risk

<<

<<+

Au

1616

Contamination Risks and 3 Cleanliness Levels污染風險與三個潔淨級別

• Clean (Lowest)• No contaminants

• Semi-Clean (Medium)• Ions of standard

materials such as Al, Cr, and Ti

• Non-Standard (Highest)• Ions of gold, copper, Ga

As, Ga Nitride, K, Na and materials/chemicals not yet classified

• 潔淨 (最低風險 )• 無污染物

• 半潔淨 (中度風險 )• 常規金屬如鋁、鉻和鈦的

離子• 非常規 (最高風險 )

• 非常規物質如金、銅、砷化鎵、氮化鎵、鉀、鈉和未分曾分類的物料或藥品的離子

1717

Process Compatibility工藝兼容性

• CMOS Compatible• Front End Processes

of ELEC508, PMOS, NMOS, and SOI

• Non-CMOS Compatible• MEMS• CMOS back-end

process• You Name it

• CMOS 兼容• ELEC508 、 PMOS 、

NMOS 和 SOI 的前工藝

• 非 CMOS 兼容• 微機電系統• CMOS 的後工藝• 不能盡錄

1818

3 Cleanliness + 2 Compatibilities = 4 Wafer Statuses 三個潔淨級別 + 兩種工藝兼容性 = 4 種晶片潔淨指數

Clean潔淨

Semi-Clean半潔淨

Non-Standard非常規

CMOS

Non-CMOS

Both兼用

CleanCMOS

CleanNon-CMOS

CleanCMOS/Non-CMOS

CleanCMOS/Non-CMOS

Clean/Semi-cleanCMOS/Non-CMOS

Clean/Semi-cleanCMOS/Non-CMOS

Semi-cleanNon-CMOS

Non-StandardNon-CMOS

Semi-clean/Non-StandardNon-CMOS

Semi-clean/Non-StandardNon-CMOS

+ 7 Combinations+ 7 Combinations+ 7+ 7 個組合個組合

1919

• Downward Compatible• CMOS -> Non-CMOS• Clean -> Semi-clean or Non-standard• Semi-clean -> Non-standard

• But not the Reverse• Non-standard -> Semi-clean ->

Clean• Once contaminated always

contaminated• Exceptions:

• Decontaminated MILC Wafers• Decontaminated wafers after Post

CMP Grinding Cleaning

• 向下兼容• CMOS -> Non-CMOS• 潔淨 -> 半潔淨或非常規• 半潔淨 -> 非常規

• 不准掉頭• 非常規 -> 半潔淨 -> 潔淨• 一被污染，永遠污染

• 例外情況：• 經過除污的金屬誘導橫向晶體化

的晶片• 經過除污的化學機械拋光晶片

Mechanism of PV Scheme工藝驗証指引的機制

2020

Decontamination除污工藝

• Wafer Status after decontamination• Clean Non-CMOS

• Not for:• Non-standard

Wafers• Almost all Semi-

Clean Wafers

• Not necessary for Non-CMOS users

• 除污後的晶片潔淨指數

• 潔淨 NON-CMOS

• 不合於：• 非常規晶片• 大部份半潔淨晶片

• NON-CMOS 使用者一般不須用此工藝

2121

Processing Requirements of individual processes個別模組要求的工藝規格

• Wetstations• Oxidation,

Diffusion and CVD• Implantation• Dry Etching• Sputtering• Photolithography

• 濕化工藝台• 氧化、擴散與化學汽相澱積

• 離子注入• 乾化蝕刻• 濺射• 光刻

2222

Wetstations 濕化工藝台

• 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 requ

ires 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 coate

d wafers at CLEAN wetstations• No Metals at the sulfuric acid bath

for resist stripping• Separation of cassettes, tools cont

ainers and gloves from those of different stations

• No lifted-off wafers put in baths• No mess left at wetstations

2323

Layout of Wetstations濕化台的分佈

2424

Labels of Wet-stations每個濕化台所用的記號

Lowest

Highest

Risks of C

ontamination

A:CMOS Cleaning Station

C:Oxide and nitride etch

B:Non-CMOS Cleaning Station

G:TMAH Etching Station

E:Semi-clean Non-metal Processing Station

D:Standard metal processing Station

Y:Semi-clean Organic Stripper

Z:Semi-clean Develop Station

Z2:Semi-clean/Non-standard Dump Rinser

F:Non-standard Processing Station

J:ASTRI’s Station (for ASTRI only)

2525

Summary of Wetstation Arrangement濕化台的調度

Non-Standard

Semi Clean

Clean

Non-Std Chemicals /Materials

Start

Ti-Silicide?

Wet-stations D, E

Liftoff?

Dump Rinsers ofWet-station FBath Z2

Std Metalse.g. Al/Cr/

Ti

CMOS?

Wet-Station D Wet-stations D, E

“Decontamina-table”

Wet-station X, G, Cand A

Yes Yes

Yes

Yes

Yes

No

No

No

No

No

Wet-station X, G, C and B

B3:Decontamination

Yes

No

Wet-station FBath Z2

Dow

nw

ard

Com

patib

leD

ow

nw

ard

Com

patib

le

Once contaminated by Non standard group (except Z2) cannot pass this line

Once contaminated by semi-clean group cannot pass this line

To find which baths you are allowed to use, look at the process historyTo find which baths you are allowed to use, look at the process history

2626

Oxidation, Diffusion and CVD 氧化、擴散與化學汽相澱積

• Wafer Substrates• Thickness• Full Wafers Preferred• Appropriate Cleaning

Processes• No Photoresist• No organic• No metals for most

furnaces• No wafers of

uncertain background

• 晶片材料• 厚度• 完整一片的晶片較合• 用適當的工藝清洗晶片• 不許有光刻膠• 不許有有機物• 大部份爐都不可入金屬• 不許有來歷不明的晶片

2727

Implantation離子注入

• 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

2828

Dry Etching 乾化蝕刻

• 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.

2929

Sputtering 濺射

• Limited Target Materials

• Thickness < 5000A• Full Wafers Preferred• No photoresist nor b

roken wafers on Semi-clean Sputterers

• Lift-off wafer in Non-Std sputterers only

• 濺射靶的材料是有限制的

• 一般厚度不多於 5000A

• 完整晶片較合

3030

Photolithography光刻

• 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• Don’t 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

3131

Contamination arising from Integration

• Inter-level Contamination• Caused by contaminants from incompatible cleanliness g

roups• 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 equipme

nt• 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

NFF Operation TrainingNFF Operation Training

Process Flow工藝流程

Process Flow工藝流程

3333

Outline

• Aim• Standard Format • Common Mistakes• Process

Guidelines

3434

Aim of Process Flows

• Functions:• Help you to plan ahea

d• Track down wafer mo

vement • Reduce uncertainty• keep the unqualified

away from NFF• Aim:

• Control Contamination

3535

Sample Process Flow

3636

Standard Format

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

3737

Mistake 1 - Oversimplification

3838

Mistake 2 – Wrong Initial Wafer Status

3939

Mistake 3 – Incompatible equipment Status

4040

Mistake 4 - Double-side PR Coating

4141

Mistake 5 – Wrong PR Stripping

4242

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

4343

Process Guidelines

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

Polymer Removal

• 3 Etchings to Etch Through Wafers

• Liftoff• Non-standard

Metal (Gold)

4444

Cleanings

• Sulfuric Clean (CMOS)• RCA2(Decontaminatio

n)• Pre-diffusion Clean (C

MOS)• Pre-deposition Clean

(CMOS)• Sulfuric Clean (Non-CM

OS)• Post-Metallization Clea

n• Mask Cleaning

4545

Sulfuric Clean (CMOS)

• CMOS Only • No photoresist, metals nor silicides

• A1:H2SO4:H2O2 + A2:HF:H2O 1:50• Removing organics and gross conta

minants e.g. scribe dust.• H2SO4 – reduces organics to carbon• H2O2 – oxidizes carbon to form CO2

4646

RCA2(Decontamination)

• CLEAN or Decontaminatable Wafers• No photoresist, metals• B3:H2O:H2O2:HCl at 70 ºC (fresh)• Drain after use• Removes metallic contaminants and alka

li ions• HCl – reacts with most metals to form solubl

e chlorides• H2O2 – acts as a buffer/oxidant

4747

Pre-diffusion Clean (CMOS)

• CMOS Only• No photoresist, metals nor silicides• Process:

• A3:H2SO4:H2O2 – cleans organics• Dump rinse• A2:HF:H2O (1:50)• Dump rinse• Spin Dry

• Prior to the growth of high quality oxide

4848

Pre-deposition clean (CMOS)

• CMOS only• No photoresist, metals nor silicides• Process:

• A1:Sulfuric Clean• Dump rinse• A2:HF:H2O (1:50) cleans native oxide

• Prior to deposition

4949

Sulfuric Clean (Non-CMOS)

• Clean MEMS only• No photoresist, metals nor silicides• B1:H2SO4:H2O2 + B2:HF:H2O 1:50• Removing organics and gross conta

minants e.g. scribe dust.• H2SO4 – reduces organics to carbon• H2O2 – oxidizes carbon to form CO2

5050

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

5151

Mask Cleaning

• Semi-Clean• Mask Only• Process:

• Y2:MS2001• Dump-rinse• Dry by an N2 Gun• Oven

5252

Resist Strips

• Sulfuric Acid (E4)• CLEAN• SEMI-CLEAN Without Met

als/ Silicides• MS2001 (Y1)

• Standard Metals• Semi-Clean

• O2 Ashers + Wet (E4, Y1)• High-temp Treated PR

• Non-Standard W2• Non-Standard

5353

Resist Strip (General)

• Semi-Clean and Clean• No metal nor silicide, nor ITO, nor heavily

doped/implanted photoresist, nor undensified doped LTO

• Process:• E4:Sulfuric Acid• Dump-rinse• Inspection

5454

Resist Strip (post implatation or high temp treatment)

• Semi-Clean and Clean• No metal nor silicides• Process:

• O2 Plasma ashing• E4:Sulfuric Acid/Y1:MS2001(it depends)• Dump-rinse• Inspection

5555

Resist Strip (Standard Metals)

• Standard Metals• No samples undergone liftoff• Process:

• Y1:MS2001• Dump-rinse• Spin Dry• Inspection

5656

Resist Strip (Non Standard)

• Standard Metals• No samples undergone liftoff• Process:

• W2:MS2001• Dump-rinse• Spin Dry• Inspection

5757

Post ICP Deep Silicon Etch Polymer Removal

• Clean CMOS/Non-CMOS• Wetstation X• Process

• EKC265 Stripper• 70 C• 20 mins• Inspection

5858

Etching Through Wafers

• Dry Etch• Deep-silicon Etcher• Under Installation

• KOH• Etching furiously • Non-standard

Process

• TMAH• CLEAN Process• Nitride + Oxide as

Etching Masks

5959

ICP Deep Silicon Etcher

Substrate

Sub- strate

Method 1 Method 2

Substrate

*8 um thick Photoresist

Oxide

Substrate

Scratches

Particles generated from here

*Note: The manual photoresist developing or polymer removal must be done at Wetstation X

6060

KOH Etching – Non-standard

Oxide Substrate

Nitride

Substrate

Photoresist

Substrate

strate Ideal

Scratches

What if resist is scratched away?

Sub-

ParticlesGeneratedFrom here

Sub-

6161

Sub-

TMAH Etching

Substrate

Nitride

strate

Oxide

Ideal

Photoresist

What if resist is scratched away?

Substrate

Substrate

ParticlesGeneratedFrom here Scratches

6262

Particulate - liftoff

Substrate

Substrate

Substrate

Photoresist

Photoresist

Photoresist Residue

Metal

Metal Residue

Step 1

Step 2

Step 3

6363

Particulate – liftoff (con’t)

• 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 can’t

stop generating contaminants. • Don’t even think about putting samples

into any processing baths, That is extremely irresponsible!

6464

Metallic Contaminant – Gold

• Gold Ions• Most-Contaminating because of its high mob

ility• Easy to spread into the atmosphere, if heate

d• From films, equipment, tools, containers and

cassettes, which are in contact with Au+ ions• Totally incompatible with almost all process

es and equipment except for• Bath Z2• Wetstation F• Thermco E4: Thermal Anneal (Gold)

6565

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!

NFF Operation TrainingNFF Operation Training

Do’s and Don’t’s 規矩

Do’s and Don’t’s 規矩

6767

Chemicals and Wetstations

• Don’t bring your own chemicals or materials into NFF unless you have approval

• Don’t take any chemicals or materials away. That is theft.

• Don’t leave chemical bottles on the floor

• Never put into CLEAN baths wafers that have undergone metallization.

• Don’t leave anything, especially incompatible materials, on the top of wet-stations.

• Disposal of HF and BOE must be done by trained persons

• Don’t be so irresponsible as to leave down the tools you have used and go away

• Don’t 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

6868

Operation

• Store wafers of different wafer status in separate boxes

• Always inspect your wafers after a resist strip to ensure cleanliness

• Don’t put non-standard materials, especially gold into semi-clean and clean baths

• Don’t 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

6969

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

7070

Personal

• Don’t 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. Don’t 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

• Don’t stay in the laboratory if not necessary. NFF is not a meeting place!

7171

Useful Webpages

• NFF User Guide (well underway)• Hook up to http://www.nff.ust.hk and then click on “Safet

y 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

NFF Operation TrainingNFF Operation Training

Q&A答問時間

Q&A答問時間