Immersion Lithography Status on XT:1250Di - Sematech

© imec 2005 

<strong>Immersion</strong> <strong>Lithography</strong> 

<strong>Status</strong> on XT:1250Di 

M. Maenhoudt, S. Cheng, D. Laidler, D. Van 

Den Heuvel, D. Vangoidsenhoven, G. 

Storms, P. Leray, IMEC 

R. Moerman, B. Streefkerk, ASML

History 

Februari 2005: installation of one of the first immersion 

scanners XT:1250Di @ IMEC 

IIAP program focussing on 

� Resists and processing 

� Defectivity 

� Imaging 

� Scanner 

� Hyper NA reticles 

Original: early immersion configuration 

Since Aug. ‘05: state-of-the-art immersion configuration 

(first in the field) 

� Modified wafer stage immersion concept 

� Improved water containment 

� See presentation B. Streefkerk (Wednesday 3pm) 

� <strong>Immersion</strong> parameters still being optimised 

© imec 2005 M. Maenhoudt – 2nd International Symposium on <strong>Immersion</strong> <strong>Lithography</strong> 2

CDU 

Overlay 

defectivity 

Outline 


CDU 

Overlay 

Defectivity 

Outline 


Illumination condition: 

Annular, NA = 0.85, σ= 0.93 / 0.69 

Binary Reticle 

Target CD : 90nm, 1:5 

Resist Process 

77nm BARC, 150nm PAR817, 32nm TCX007 

Metrology and sampling plan 

�26x33mm field size, 

�57 full fields and 26 partial fields, 

�Horizontal and vertical, 

�Measurement sampling 

CD-SEM = 1 point per field, 

Scatterometry = 7 points / slit; 8 points / scan 

Process conditions 


Chuck Deformation Map (LVT results) 

Chuck 1 Chuck 2 

3 sigma focus deviation across the wafer is

Annular, NA = 0.85, 

σ= 0.93 / 0.69, Binary 

Target CD : 90nm, 1:5 

77nm BARC, 150nm 

PAR817, 32nm TCX007 

57pts/field, 63 fields 

measured using 

scatterometry, total 

points measured is 

~3500points. 

Vertical 

Full Field, Full Wafer CDU 90nm 1:5 

Horizontal 

3σ = 3.31nm 3σ = 3.14nm 

CDU fingerprint for both horizontal and vertical orientations is 

similar – PEB hotplate fingerprint to be optimised 

3σ CDU for both orientations is

Vertical 

MEAN = 92.1nm 

3σ = 0.99nm 

Horizontal 

MEAN = 91.6nm 

3σ = 1.1nm 

Intrafield CDU 

Difference in mean Intrafield CD of horizontal and vertical 

orientations is negligible. 

3σ intrafield CDU is ~1nm for both horizontal and vertical 

orientations. 


CDU 

Overlay 

defectivity 

Outline 


Full Batch Matched Overlay on XT:1250Di - 

Procedure 

Reference wafers exposed on a dry tool using a standard first 

layer print, in the same way as normal production, 

Pattern etched into silicon to a depth of 120nm, 

Reticle used is a modified version of the standard ASML overlay 

reticle which includes scribeline marks, 

Exposed in a full batch on XT:1250Di in normal lot operations, 

Alignment performed using VSPM-AH325374 mark type, Red 5th 

Order, 16 scribeline mark pairs and 4 parameter model. 

Measured on KLA-Tencor Archer AIM using a bar in bar structure, 

Analysis performed using Mono-Lith for Windows v6.3 from 

INFICON. 


XT:1250Di Matched Overlay Performance - 

current configuration to dry tool 

|m|+3σ: 

X = 17nm, Y = 15nm 

49 Points per Field, 71 Fields per Wafer, 10 Wafers. 

Correctable (Systematic) errors removed, based on average 

across lot. 


Grid Residuals (1σ) Across Batch - current 

configuration 

Residual (nm) 

25 

20 

15 

10 

5 

0 

0 1 2 3 4 5 6 7 8 9 10 11 

Wafer Number 

Residual X Residual Y 


CDU 

Overlay 

Defectivity 

Outline 


Contributions from 2 sources: 

Scanner 

� Improvements in hardware 

Materials 

� Dry resists with top coat (developer soluble) 

� <strong>Immersion</strong> dedicated resists 

<strong>Immersion</strong> defectivity 


Defect sources 

1. 193nm resist + track process related defects (also 

seen with dry exposures) 

� (micro-)bridging, particles 

� No distinction from immersion possible at Imec 

2. Particles from local enclosure 

� Also present in dry exposures, but now more likely to be 

transported onto wafer 

� Show up as micro-bridging when removed during development 

3. <strong>Immersion</strong> specific defects 

� Water marks 

� Drying stains 

� Bubbles 

� Micro-bridging between narrow lines 

� Line slimming 

� Line widening 


Non-immersion: Particles 

Defect classes 

Candidate immersion: Micro- & non-round bridging 

<strong>Immersion</strong> specific: 

+ bubbles 

+ line slimming 

+ line widening 


But first! 

Defect numbers are difficult to compare if different targets are 

measured. 

0.2μm features and 

large open areas 

� much less 

bridging (candidate 

immersion defects) 

observed 

Use targets that are relevant for the technology node where the 

tool is developed for! But should not be sensitive to imaging failure 

modes 

⇒ All further data with 100nm L/S reticle, fully covered with lines 


Exposures: 

Experimental 

ASML XT:1250Di scanner, state-of-the-art configuration, 

300mm/s scan speed 

TEL Clean Track ACT12 

Reticles: 

100nm L/S (metro-reticle): full field and 10x10mm2 

CH: 80, 100 and 120nm CH on pitches 250nm, 500nm, 1000nm 

(K-T viashrink) 

Metrology: 

KLA2351 BF defect inspection, 0.16μm pixel size 

� downto 80nm defects can be measured 

iADC classifier 

KLA eCD2 (SEM review) 

KLARITY 2.5.0.17 


Comparison early – current configuration: 

full field exposures 

Full field exposures, same process (PAR817 + TCX007) 

Early config., typical wfr. 

± 2 defects/cm2 

Total # ≈ 1000 

Current config., champion wfr 

0.037 defects/cm2 

Total # = 18 


defect density (1/cm2) 

0.09 

0.08 

0.07 

0.06 

0.05 

0.04 

0.03 

0.02 

0.01 

Classification full field, current config. 

0 

nonimmersion 

candidateimmersion 

immersion total 

Good reproducibility for candidate immersion and 

immersion defects 

© imec 2005 M. Maenhoudt – 2nd International Symposium on <strong>Immersion</strong> <strong>Lithography</strong> 20 

wfr 1 

wfr 2 

wfr 3

Comparison early – current configuration: 

small field 

Small field (10x10mm2) exposures, same process 

(PAR817 + TCX007) 

Early config. Current config. 

1 defects/cm2 0.12 defects/cm2 


NO bubbles with current configuration! 

Classification results 

Early config. Current config. 

24 bubbles 

0 bubbles 


Small field vs full field 

Small field is needed to inspect till edge of wafer, but not typical 

production layout 

BUT: 8.3 times smaller die results in increased defect count by 

factor ±5 


0.45 

0.4 

0.35 

0.3 

0.25 

0.2 

0.15 

0.1 

0.05 

0 

non-immersion candidateimmersion 


full field wfr 1 



small field 

small field wfr 1 





Conclusion: amount of (candidate-) immersion defects increase for 

higher number of scans/area unit 


x5

<strong>Immersion</strong> resist performance 

No TC used, 2 different resists investigated 


0.4 

0.35 

0.3 

0.25 

0.2 

0.15 

0.1 

0.05 

0 


RE11 

RE12 

PAR817 + TCX007 



New immersion resists show promising performance, but are not 

yet as good as IMEC std. process (dry resist + TC) for immersion 

More info: see posters H-W Kim, N. Stepanenko, W. Fyen 




0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

0 

PAR817 + TC6 

PAR817 + TCX007 



Main difference in candidate immersion defects: 

micro-bridging� bad compatibility TC/resist? 

Mechanisms still under investigation. 

More info: see posters N. Stepanenko and W. Fyen 

Different TC 



Contact hole defectivity 

Also promising results for 100nm ch (AJ2211 + TCX007) 



0.35 

0.3 

0.25 

0.2 

0.15 

0.1 

0.05 


0 

non-immersion candidate 

immersion 

immersion 

related 

total

Summary 

The state-of-the-art immersion configuration on IMECs XT:1250Di 

gives 

�Very good CDU performance : 

� 3σ CDU for both orientations are

Summary 

The state-of-the-art immersion configuration on IMECs 

XT:1250Di gives 

�Very good CDU performance : 

� 3σ CDU for both orientations are

IMEC: 

� ASML team on-site 

� B. Baudemprez (track) 

acknowledgements 

� N. Vandenbroeck, S. O’Brien, F. Van Roey, M. Kocsis, N. 

Stepanenko 

� K. Ronse 

ASML: 

� Teams in Veldhoven and Leuven

Immersion Lithography Status on XT:1250Di - Sematech

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