Current development status of Shin-Etsu EUV pellicle

Transcription

1 Current development status of Shin-Etsu EUV pellicle Advanced Functional Materials Research Center 1

2 Why Pellicle for EUV Lithography? Extensive studies on particle addition during reticle transfer have been done so far with superior results. What about particle addition or carbon contamination during EUV exposure? Most EUV programs have been in progress based on the assumption that there is no particle adders in EUV chamber But what if particle adders can not be avoided? We have been studying EUV pellicle s possibility as a back-up technology since

3 History of of Shin-Etsu Pellicle Started R&D in 1992 Production of ArF Pellicle in 1999 Production of pellicle for ArF immersion in ? Started pellicle Sales for G line, I line and KrF in 1995 Production of pellicle for Large LCD in 2006 What is is next next to to ArF ArFimmersion? No No pellicle? or or EUV EUV pellicle? 3

4 Absorption of of Inorganic Absorption Coefficient (k) Palik et al. Optical constants of solids Single crystal Silicon is is chosen as as EUV pellicle membrane because 4

5 Shin-Etsu has extensive knowledge and experiences on thin silicon film substrates such as SOI SOIfor for high high performance LSI LSI Silicon on on anything (SOA) for for MEMS MEMS applications Silicon on on Quartz (SOQ) for for advanced optics optics Silicon on on sapphire (SOS) for for RF RF applications Shin-Etsu s Si thin film technology has been applied to EUV pellicle fabrication! 5

6 Proposed structure of of Shin-Etsu EUV pellicle Particle filter w/ metal fiber Single crystal Si Anti-oxidation layer (e.g. Ru,Rh) Mask blank Air Mechanical support (Honeycomb) ML Membrane and and honeycomb are are made made with with the the same same material(=single crystal crystal Si) Si) so so that that the the pellicle pellicle can can accommodate temperature change change during during continuous exposure 6

7 Key parameters EUV light Open area on pellicle Honeycomb width EUV pellicle Honeycomb Honeycomb Height Height (not (not discussed discussed here) here) Actual open area on photomask Si membrane Si honeycomb Thickness of of Si Si ML Thickness of Si membrane & Honeycomb width are the key parameters for higher transmission! 7

8 Scanning Electron Micrograph (SEM) of of EUV pellicle Honeycomb Si membrane Sample was intentionally broken for SEM observation 8

9 Major things to to be considered 1. Mechanical strength: can stand 10G acceleration? 2. Transmittance: >90% for single-pass or >80% for double-pass 3. Shadow effect: Wide honeycomb influences patterning on wafer (shadow effect). which has to be minimized. additionally 4. Stability against high-power EUV radiation Transmittance Transmittance Shadow Shadow effect effect Mechanical Mechanical strength strength Complicated trilemma has to be considered! 9

10 History: Size evolution of Shin-Etsu EUV pellicle Tsi=200nm October 2009 August June June cm Development of EUV pellicle with single crystal silicon membrane Shoji Akiyama, Yoshihiro Kubota 2010 International EUVL Symposium Kobe, Japan 10

11 History: Thickness reduction of Si membrane Oct. Oct Tsi=200nm Thoneycomb=100um July July Tsi=100nm Thoneycomb=50um Oct.2010 Tsi=70nm Thoneycomb=50um Development of EUV pellicle with single crystal silicon membrane Shoji Akiyama, Yoshihiro Kubota 2010 International EUVL Symposium Kobe, Japan 11

12 Mechanical strength: Computer simulation Computer simulation was was done done as as to to how how much stress is is induced to to which part part of of honeycomb 12

13 Mechanical strength: vibration test EUV pellicle Vacuum chamber Vibration motor Top view of chamber Vacuum gauge No No damage damage was was observed after after 6G 6G (Max (Max power) power) vibration 13

14 Computer simulation on mechanical strength -optimization- Computer modeling Numerical analysis Feedback Experiment HoneyComb Opening ( % ) Transmission H=20μm H=30μm H=50μm Analysis Check Internal Stress ( MPa ) Max. Stress induced Vacuum chamber High-speed vibrator 14

15 Patterning images with EUV pellicle by computer simulation With WIDE honeycomb With NARRROW honeycomb Wide honeycomb DOES affect patterning (Shadow effect). Minimizing honeycomb width is is important challenge for for EUV pellicle 15

16 History of honeycomb structure Pitch=200um, Width=35um Pitch=200um, Width=15um Pitch=100um, Width=5um Pitch=100um, Width=3um Now in progress 16

17 Optical microscope image of the latest honeycomb structures 50x 500x 1000x 3 m width 100 m pitch 5 m width 100 m pitch Scale=5 m Scale=100 m Scale=100 m Scale=3 m 17

18 Appearance of the latest prototype 18

19 Transmittance improvement of Shin-Etsu EUV pellicle Target Target of of 1x 1x pass pass Target Target of of 2x 2x pass pass We We will will try try to to achieve >90%(single) and and >80%(double) as as soon soon as as we we can. can. 19

20 History of Geometry improvement for maximum transmittance and minimum shadow effect Si ?? honeycomb Final Final target target where where T>90% T>90% and and no no honeycomb shadow shadow on on wafer wafer 20

21 Heat load evaluation: simulation model Incident EUV light Radiation EUV- pellicle Radiation Simple model is employed based on 21

22 Heat-load simulation results Membrane + honeycomb Source power Membrane only Source power Elapsed time (msec.) Elapsed time (msec.) Honeycomb structure works as as heat heat reservoir 22

23 EUV irradiation test: experiment environment Courtesy of Kinoshita lab. U of Hyogo, New SUBARU LINIAC Synchrotron Evaluations were were done done at at New New SUBARU of of Univ. of of Hyogo (Prof.Kinoshita s lab.) lab.) 23

24 Tool outline for irradiation resistance test Synchrotron EUV pellicle Detector Courtesy of Kinoshita lab. U of Hyogo, New SUBARU 189mW/cm 2 2 EUV light lightwas irradiated onto onto EUV EUV pellicle. 100mW/cm 2 2 is is current target for for EUVL 24

25 EUV irradiation duration test result (a.u.) Courtesy of Kinoshita lab. U of Hyogo, New SUBARU No No transmittance degradation was was observed. 25

26 Summary and future plan We are now focusing to minimize the honeycomb width to eliminate shadow effect as well as to maximizing transmission (Target = 90%: single-pass). In addition to experiment, we are trying to optimize the honeycomb structure using computer simulation. We will work with ASML to evaluate our prototypes of EUV pellicle and feedback the results to next prototypes to find out the best answer for reticle protection. Thank you! 26