P. 1

Process stability control for

immersion lithography

Speaker: Chin-Yu Chang

TSMC academician

Advanced Lithography Process Department III

Nano Patterning Technology Division

R&D

P. 2

Outline

1. Immersion tool

2. Immersion material

3. Immersion process

P. 3

Scanner Defect Stability Control

Hardware Clean parts No trash cans

Water flow Soon refresh rate Flow direction Laminar flow, no dead zone

Stage movement Optimized scan/step speed, accel Optimized routing

lensUPW inlet

UPW outlet

wafer

Stage

water

Surface treatment Hydrophobic or hydrophilic Meniscus stability Less water loss Surface material endurance

Facility(UPW, Air, CO2) Supply stability Extreme clean material Filtration

P. 4

lensUPW inlet

UPW outlet

wafer

Stage

water

Functionality for Tool Maintenance

Surfactant-ASurfactant-BSurfactant-C…

in-line chemical cleaning

Contaminant removalSurfactant via recipe control

Anion, cation, TOC, metal…

Liquid particle

Immersion chamber monitor

SPC control, real time monitorTrace wafer cleannessMonitor chamber cleanness

Automatic self-clean

Keep system clean always Triggered by wafer # or time

P. 5

How to Correlate Defect to System

6250-193, SPIE 2007, FJ Liang

Robust tooling for the monitor, analysis, simulation and prediction of defect behavior

P. 6

Requirement for Track Defect Reduction Key module

Coater, developer and soaking units

Configuration Customized hardware (tube, nozzle, arm, cup, exhaust…) Optimized unit recipe & wafer flow to improve defect Innovative treatment units

Maintenance Environment control Advanced PM skills to remain baseline Exploratory methodology to qualify module performance

P. 7

Tool Stability Control

Trend Concern Possible solution

High scan speed for scanner

More defect due to water loss

1. Extra treatment before PEB

2. Resist material optimization

3. Scanner parameter tuning

CD shrinkage More pattern scum

1. Resist material optimization

2. Track process optimization

Wafer bevel cleanness quality

Particle induced pattern failure

1. Clean bevel for incoming wafers

2. New stage design to suppress wafer edge defect

Defect Inspection

Data reliability

1. Inspection tool CIP

2. Monitor methodology CIP

From defectivity point of view

P. 8

Resist Formulation Tuning

P. 9

Resist Formulation Tuning

P. 10

Spin dry

BIM process

Treatment process

PSM/ topcoat

Similar contact angle between surface and sidewall

High surface contact angle difference between surface and pattern side wall•

Developer Strategy and Challenge

Treatment:•.

P. 11

Spin dry

CH Developer Strategy and Challenge

P. 12

Commercial freezing PR tsmc

Litho- COT->EXP->Dev->HB

Freezing COT->SB->Dev->HB

Litho- COT->EXP->Dev->HB

US$ /gallon

Dispense volume

Cost /wafer

Should be OK

DP process

4. Reversal process

3. Material cost comparison

2. Process scheme

1

Freezing Process for DPT

P. 13

Commercial freezing PR tsmc

1 Top-loss issue

2 Line-end loss

3 1st pattern e-beam damage

Serious e-beam damage was shownin JSR freezing material

No PR damage at line pattern, butPR damage at island pattern.

4 1st CD-bias after freezing <±2nm bias, after 2nd PR preparation<±2nm bias, after 2nd PRpreparation

5 1st/2nd PR Etching resistance Different, only 1st PR is frozen. Same, both DP PRs can be frozen.

6Risk of residual freezingmaterial

It will cause scum defect if residueis present.

No problem!! It will evaporateduring baking, due to boilingpoint=118oC.

7 Overlay criteria < 6nm < 6nm

Top issues

P. 14

Implant Layer Scum Reduction

NPR Treatment Modified PR

Advantage

Disadvantage

Good profile, CDUNo scum, poison issuePrecise implant control

New processSubstrate damage?COO

Good top view profileNo scum

Poor undercut profilePR maturity

Scum, poison issuePoor optical intensity in small trenchChemical diffuse difficultyDBARC iso dense bias

P. 15

wafer

IH

Lens

Immersion defect analysis – the interaction between tool, material and process

LensContamination source:Leaching PAG, ParticleClean strategy: chemical clean

Immersion hoodContamination source:resist, tool, dry/wet interfaceClean strategy: mechanical or chemical clean

stageContamination source:WS, IH, resistClean strategy: mechanical or chemical clean

stage

IH

Pattern defectSource:IH, stage

Resist process Contamination source: EBR, film stack, resist leaching

P. 16

OM wafer edge

TARC BARC

PR

Conv.

New

SEM Wafer edge

BARC

PR

defect

Immersion Process- EBR ProcessOM picture SEM pictureEBR Process

Film stack:

Film peeling StressAdhesionSwellingHydrophobic/philic

P. 17

Sample 2

Lens Cleaning Chemical Performance Sample 1

P. 18

Pre Scanner

0.65 AmpMega sonic

0.9 AmpMega sonic

Cleaning 1 Cleaning 2

112

205

641

645

9

3

34

247

85%87%89%91%93%95%97%99%

0.65 0.7 0.75 0.8 0.85 0.9 0.95 1

Particle remove rate vs. mega sonic power

ampere

RR.

P. 19

Particle accumulation and cleaning

Lens

fluid in fluid out fluid out

1cmDI in out

lens Water control apparatus Background facility

Immersion head

Lens

fluid in

P. 20

Wafer

Immersion head

water drop residue after immersion exposure

Leaching from resist or contamination from air influence the CAR(chemical amplify reaction) Stage movement direction

Water drop

Wafer

PR layer

Watermark defect mechanism

P. 21

h

w

D

F

Pattern collapse, defect and its solutions

ResistConventional: Improve resist rigidity

Our approach 1. Change the surface

condition to decrease the swelling and increase surface hydrophobic.

2. Special formulation to decrease the capillary torque force

DeveloperConventional Surfactant rinse

Our approach New surfactant for collapse and defect improvement

F=6Stcos/D(AR)2

AR: aspect ratio

: contact angle

D: space width

BARCConventional: Only consider the n,k

value

Our approach 1. Adhesion

improvement -- Tail structure, Porous structure

2. Surface condition improvement -- Leaving group structure, polarity switchable group

P. 22

std PR Remarkpuddle time (s) Std 15 10 5EOP (mj) 32 30 30.5 31LWR (nm) 11.6 10.4 10.5 10.9collapse DOM (nm) 2 5 5 5 mask SPEC : CD+-3nm (1X)collapse DOW (nm) 68 76 76 76 CD : 60nm+-6nmMEEF 3.84 3.6 3.48 3.68

std. PR + CR

TMAH DI water rinse Spin- dry

Chemical treatment

Pattern collapse and LWR