World-wide Standardization Effort on Leaching Measurement Methodology

Transcription

1 World-wide Standardization Effort on Leaching Measurement Methodology Roel Gronheid 1, Christina Baerts 1, Stefan Caporale 2, Jim Alexander 2, Ben Rathsack 3, Steven Scheer 3, Katsumi Ohmori 4, Bryan Rice 5 1 IMEC 2 Rohm & Haas 3 TEL 4 TOK 5 Sematech

2 Acknowledgments Material Suppliers TOK JSR Fuji Film Shin-Etsu DongJin Sumitomo Rohm & Haas AZ-EM DuPont Analytical Labs RIC MPI Research (Exygen) Scanner Suppliers ASML Nikon Canon Matt Colburn and Irene Popova (IBM) for helpful discussions All members of the Leaching Standardization WG for their input Special thanks to Akimasa Soyano (JSR Belgium) for assistance with shipments for Round Robin experiments

3 Outline Introduction Leaching Measurement Requirements Water collection standardization dynamic WEXA (-1 and -2) TOK s method Water analysis standardization Conclusions and Outlook

4 Outline Introduction Leaching Measurement Requirements Water collection standardization dynamic WEXA (-1 and -2) TOK s method Water analysis standardization Conclusions and Outlook

5 Introduction Leaching specifications are needed for lens warranty and because leaching is a suspected cause of particle defects Tool vendors specify the allowable leaching levels at very short water/resist contact times ASML, Nikon : Initial leaching rate in mol/cm 2.s Leaching results that were initially shown by resist vendors only reported leaching at much longer water/resist contact times Leaching saturates rapidly and is not a linear process IMEC procedure was compared to data of 8 different vendors (A-H) Good correlation (<25% offset) obtained with some vendors Poor correlation with others ratio IMEC leaching/vendor leaching A 3.28 B 0.25 C 0.94 D 0.40 E 0.76 F NA G 0.95 H 0.60

6 Kyoto Workshop on Leaching Measurements 5 resist vendors and 3 IDMs showed their leaching procedure ASML and Nikon detailed their requirements Unanimous agreement on need for standardization Tool vendors need to provide further details on their leaching specification: PAG anion, cation, quencher leaching? Others? Before or after exposure?

7 Outline Introduction Leaching Measurement Requirements Water collection standardization dynamic WEXA (-1 and -2) TOK s method Water analysis standardization Conclusions and Outlook

8 Requirements Requirements for standardized method: Inexpensive Allow for in-situ exposure Simple Liquid analysis method included Dynamic capabilities HIL capabilities Good repeatability Minimize cross-contamination Easily available Experimental conditions defined Two water collection techniques were identified as most suitable candidates: dynamic WEXA (IBM/IMEC) and TOK s method ASML, Nikon, Canon agree to target PAG cation leaching on unexposed resist material

9 Lens contamination tests Influence PAG-type, 1.4 Gshot exposure 437 ppb TPS nona-flate Photo Acid Generators Photo Acid 320 ppb TPS triflate 27 ppb DTI nonaflate O O S O F 2 C C F 2 F 2 C CF ppb triflic acid photoacid no deposition no exposure no deposition IMEC Immersion rd International Symposium Symposium on Immersion Lithography 2006 I + in exposure region no deposition only outside exposure are deposition including Stainless Steel sample cell

10 Dynamic Leaching Procedure (DLP) Immersion Interference Printer is used Primed silicon Resist Showerhead R. Gronheid et al. SPIE 2006, Vol. 6154, 61541I

11 DLP - Results 2.5E-11 1.E-11 Fit data to A-A*exp(-Bt) leaching (mol/cm 2 ) 2.0E E E E-12 9.E-12 8.E-12 7.E-12 6.E-12 5.E-12 4.E-12 3.E-12 2.E-12 1.E-12 leaching rate (mol/cm 2.s) Generally more robust than rate 0.0E time (s) 0.E+00 A = 2.1E-11 mol/cm 2 Plateau level B = 0.41 s -1 Time component A*B = 8.8E-12 mol/cm 2.s Leaching rate Leaching in 1 st sec: 7.2E-12 mol/cm 2

12 Outline Introduction Leaching Measurement Requirements Water collection standardization dynamic WEXA (-1 and -2) TOK s method Water analysis standardization Conclusions and Outlook

13 Outline of TOK Leaching Analysis TOK standard condition Wafer preparation - Wafer size - Sample - Softbake - Exposure - PEB : 200&300mm compatible : Resist, Topcoat, etc : Recommended bake temp. : ex situ open-frame exp. : no PEB Sampling - Tool : SES-VRC310S in chemical chamber - DI-water : 150uL/wf. - Contact time : 0.99s/cm 2 - Scan speed : 12mm/s - Sampling area : cm 2 Top View Analysis - Tool - Compound - Sample - Method : Agilent-HP1100 in chemical chamber : PAG anion and cation,, Amine : 7.5 times diluted by DI-water : Calibration curve Analysis Tool (LC-MS)

14 Dynamic WEXA-1 Only smallest cell is used for the analysis, because of nonuniform flow in the larger cells Flow Rate = 5.1 ml/min Outlet Inlet Based on original static WEXA method: W. Hinsberg et al. SPIE 2004 vol. 5376, 21 Simulations courtesy of

15 Dynamic WEXA-1 5ml/min Flow rate ~8sec contact time 40ml/min Flow rate ~1sec contact time

16 Results DLP vs WEXA-1 vs TOK Anion analysis 3.5E E-11 leaching (mol/cm 2 ) 3.0E E E E E E E+00 DLP WEXA TOK Resist1 1wt% PAG leaching (mol/cm 2 ) 9.0E E E E E E E E E E+00 Resist2 4wt% PAG DLP WEXA TOK time (s) time (s) leaching (mol/cm 2 ) 2.0E E E E E E E E E E E+00 DLP WEXA TOK Resist3 8wt% PAG time (s) Resist1 Resist2 Resist3 DLP WEXA TOK 1st second (mol/cm2.s) 5.81E E E-12 initial rate (mol/cm2.s) 6.84E E E-12 DLP WEXA TOK 1st second (mol/cm2.s) 2.48E E E-12 initial rate (mol/cm2.s) 3.34E E E-11 DLP WEXA TOK 1st second (mol/cm2.s) 5.08E E E-11 initial rate (mol/cm2.s) 6.86E E E-11

17 Results Results from WEXA-1 and DLP compare reasonably well for leaching in 1 st second. DLP gives consistently higher leaching than WEXA-1 at longer contact times Sample concentration is higher for DLP than for WEXA-1 DLP will have better detection limit and repeatability Generally more noise on cation analysis (also see water analysis round robin) TOK method gives consistently higher results Also dynamic behavior is different. Typical contaminant concentration ~100ppb DLP WEXA-1 contact time conc (ppb) contact time conc (ppb)

18 Water Collection Standardization Drawbacks of dynamic WEXA-1 User friendliness Collect all required data from a single wafer Detection limit Collect more leached material in the water, without increasing the water resist contact time Dynamic WEXA-2: longer and more shallow cells, all of identical dimension

19 Results Anion analysis leaching (mol/cm2) Resist 1 3.0E E-12 WEXA-1 2.0E-12 WEXA-2 1.5E E E E time (s) leaching (mol/cm2) Resist 3 1.8E E E-11 WEXA-1 1.2E-11 WEXA-2 1.0E E E E E E time (s) Resist 3 + TC1 leaching (mol/cm2) 9.0E E E E E-14 WEXA-1 4.0E-14 WEXA-2 3.0E E E E time (s) Resist 1 WEXA-2 WEXA-1 time (s) conc (ppb) time (s) conc (ppb)

20 Simulations on Water Collection Method At a similar contact time (2 sec), Dynamic WEXA-2 has a has 2x higher average velocity than dynamic WEXA-1 due to reduced size, even though the flow rate is reduced (13 ml/min vs 20 ml/ min) This drives WEXA 2 to have a 1.5x longer diffusion time to fill the 1 ml vial Can probably be compensated by different definition of contact time 1.20E E-11 Concentration (mol) 8.00E E E E-12 WEXA1 WEXA2 0.00E Run time (s)

21 Outline Introduction Leaching Measurement Requirements Water collection standardization dynamic WEXA (-1 and -2) TOK s method Water analysis standardization Conclusions and Outlook

22 Water Analysis Standardization 1 st Round Robin Experiment 9 solutions with contamination concentrations ppb were prepared and divided at RIC and sent out to 12 laboratories worldwide Samples were analyzed for PAG cation (TPS; triphenylsulphonium) and PAG anion (PFBuS; per-fluorobutylsulphonate or nonaflate) Each Laboratory used its own best known procedure for analysis

23 Water Analysis Round Robin 1 st Round Robin Relative results are given here (conc measured /conc nominal ) #1: blank No data for Labs H, I, J, K PAG cation relative concentration Increasing concentration A B C D E F G H I J K L

24 Water Analysis Standardization Conclusions from 1 st Round Robin Significant variation seen between different laboratories Two likely causes suggested: 1) Variation in quality (purity) of raw PAG material; 2) Procedure for detector calibration may induce variations 2 nd Round Robin Experiment 9 solutions with contamination concentrations ppb were prepared and divided at RIC and sent out to 12 laboratories worldwide Samples were analyzed for PAG cation (TPS; triphenylsulphonium) and PAG anion (PFBuS; per-fluorobutylsulphonate or nonaflate) Calibration samples were also provided by RIC

25 Water Analysis Round Robin 2 nd Round Robin No data for Lab J relative concentration PAG cation A B C D E F G H I J K L Increasing concentration

26 Water Analysis Standardization Conclusions from 2 nd Round Robin Good improvement in overall agreement between different sites Suggested causes play major role in variations General procedure for preparation of calibration samples needed (optimized and provided by Rohm and Haas) 3 rd Round Robin Experiment 9 solutions with contamination concentrations 1-100ppb were prepared and divided at RIC and sent out to 12 laboratories worldwide Samples were analyzed for PAG cation (TPS; triphenylsulphonium) and PAG anion (PFBuS; per-fluorobutylsulphonate or nonaflate) Samples for detector calibration were prepared according to optimized procedure by

27 Water Analysis Round Robin 3 rd Round Robin No data for Labs B, I, J 4 PAG Cation A relative concentration B C D E F G H I J K L M Increasing concentration Note: Sample 7 showed consistently low cation results. Probably the cation was decomposed during samples preparation.

28 Water Analysis Standardization Conclusions from 3 rd Round Robin Optimized procedure results in much better agreement between different sites compared to Round 1, (and similar to Round 2) Caution1: The current procedure is only optimized for TPS-PFBuS. Other PAG salts may need a different procedure. This is difficult to optimize, since many PAG structures are confidential Caution2: No procedure has been obtained for quencher analysis. A far wider range of chemistries is used for quenchers than for PAG (many of which are confidential), so it is difficult to pick a generic one Initial Round Robin results on (amine type) quencher analysis showed much higher detection limit and even larger variation between labs than for PAG. Further optimization was not pursued

29 Conclusions and Outlook Sensitivity of dynamic WEXA-2 has improved by ~3-5x compared to dynamic WEXA-1 Dynamic WEXA-2 almost meets same sensitivity as DLP Dynamic WEXA-2 design appears most attractive for water collection standardization Simulations will assist in choice of proper contact time definition Several instruments will be built and distributed among interested participants of the WG Procedure for water collection with dynamic WEXA-2 will be made available Round Robin experiment will be done to determine reproducibility of combined water collection + analysis (Q4 2007)

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