1. BCAM 1 A Physically Based Model for Predicting Volume Shrinkage in Chemically Amplified Resists Nickhil Jakatdar, Junwei Bao, Costas Spanos University of California, Berkeley Ramkumar Subramanian, Bharath Rangarajan Advanced Micro Devices Andrew Romano Clariant Corporation May 19th, 1999

2. BCAM 2 Motivation There is about a 5% - 15% volume shrinkage in chemically amplified resist systems Volume shrinkage and acid diffusion affect feature profile after development Acid diffusivity and other resist quantities can be extracted from modeling the volume shrinkage

3. BCAM 3 Outline Background Proposed Physical Mechanism Reducing Parameter Dimensionality Experiment and Simulation Framework Results Conclusions

4. BCAM 4 Background - Volume Shrinkage

5. BCAM 5 Proposed Physical Mechanism u w v Resin, side-chains, generated acid Acid diffuses and attacks side chains causing deprotection Volatile group and free volume formed Volatile group diffuses Volatile group leaves resist film Polymer relaxes (free volume collapses) Resist Volume Shrinkage

6. BCAM 6 Proposed Physical Model u = acid concentration v = percentage deprotection w = volatile group concentration h = hole concentration  = volume element

7. BCAM 7 Proposed Mechanism Step 1: Acid Diffusion u -- acid

8. BCAM 8 Proposed Mechanism Step 2: Deprotection u -- acid v -- deprotection w -- volatile group h -- hole (free volume) t0 t0+  tt0+2  t w w w w w w w w w w w

9. BCAM 9 Proposed Mechanism Step 3: Free Volume Relaxation h -- hole (free volume) t0 t0+  t Volume Shrinkage

10. BCAM 10 Boundary & Initial Conditions

11. BCAM 11 Reducing Parameter Dimensionality There are 10 parameters in the model to be fitted –k 1, k 2, k 3, k 4, k loss, D u0, a, D w, h 0, C Some parameters can be extracted from other experiment –Nickhil Jakatdar, etc., “A Parameter Extraction Framework for DUV Lithography Simulation”, SPIE ’99, Metrology, inspection, and process control for microlithography XII Global optimization techniques can be used for parameter extraction

12. BCAM 12 Extracting C and k 2 Exposure Dose (mJ/cm 2 ) Deprotection 140C 135C 120C 110C

13. BCAM 13 Global Optimization Technique Works for complex, non-linear multi-dimension problems. Finds the global minimum with certainty given infinite time. cost parameter

14. BCAM 14 Parameter Extraction Framework Dose to acid converter & known parameters Experimental thickness loss data Optimization Engine (ASA) Volume shrinkage simulator Resist parameters to be extracted _

15. BCAM 15 Concentration of Components in PEB Acid Deprotection Volatile Group Free Volume t=16 sec t=32 sec t=48 sec t=64 sec t=80 sec

16. BCAM 16 Experimental vs. Fitted Thickness Loss PEB time (sec) Thickness loss (nm) 3.2mJ/cm 2 4.0mJ/cm 2

17. BCAM 17 Experimental vs. Fitted Thickness Loss (Dynamic) Dose = 9.5 mJ/cm 2 Dose = 8 mJ/cm 2 AZ 2549 at 110 C PEB PEB Time (sec) Thickness Loss (nm)

18. BCAM 18 Conclusion A dynamic physical model for volume shrinkage during PEB in CARS has been proposed. The proposed model successfully predicts the volume shrinkage in high activation energy resist systems. Resist parameters were extracted using a global optimization technique. This work was funded by the California Industry and the State of California through the UC-SMART program.