The inclusion of secondary electrons and Bremsstrahlung X-rays in an electron beam resist model

A theoretical analysis and an experimental verification have been carried out to investigate the need for the inclusion of secondary electron emission and Bremsstrahlung absorption into e-beam lithography simulations for the correct prediction of the proximity effect at high beam voltages and sub-100-nm dimensions. The experimental verification has been performed at 100 kV for a variety of exposure and development conditions for sub-250-nm features. In all cases, good agreement between simulation and experimental data has been obtained using a simplified chemically amplified resist model with the inclusion of secondary electron emission in the Monte Carlo calculations. The role of the Bremsstrahlung X-ray absorption in the resist has been estimated to be negligible. The deficiency of the model when using only primary electrons in the Monte Carlo calculations is also discussed.