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A Physically Based Model for Predicting Volume Shrinkage in Chemically Amplified Resists

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.

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A Physically Based Model for Predicting Volume Shrinkage in Chemically Amplified Resists

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

  4. Background - Volume Shrinkage

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

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

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

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

  10. Boundary & Initial Conditions

  11. Reducing Parameter Dimensionality • There are 10 parameters in the model to be fitted • k1, k2, k3, k4, kloss, Du0, a, Dw, h0, 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. 135C 140C Deprotection 120C 110C Extracting C and k2 Exposure Dose (mJ/cm2)

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

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

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

  16. Experimental vs. Fitted Thickness Loss 4.0mJ/cm2 Thickness loss (nm) 3.2mJ/cm2 PEB time (sec)

  17. AZ 2549 at 110 C PEB Dose = 9.5 mJ/cm2 Thickness Loss (nm) Dose = 8 mJ/cm2 PEB Time (sec) Experimental vs. Fitted Thickness Loss (Dynamic)

  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.

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