Softbake and Post-exposure Bake Optimization for Process Window Improvement and Optical Proximity Effect Tuning

We have shown that process effects induced by extending the softbake (SB) and post-exposure bake (PEB) temperature in the process flow of chemically amplified photoresists can lead to significant improvements in depth-of-focus (DOF) and exposure latitude (EL) and small geometry printing capability (resolution). Through careful optimization of SB and PEB temperature, dense line and space structures of 160 nm and below can be printed with substantially big process margin, using binary masks and 248 nm lithography under the half annular illumination mode. Besides, we have also shown that the optical proximity effect, namely the non-linearity, proximity bias and line-end shortening in specific is tunable by changing the SB and PEB temperatures. The main objective of this study is to demonstrate how, using 248 nm lithography with binary masks and with a moderate resolution enhancement technique (RET); the process latitude can be improved besides minimizing the impact from optical proximity effect.