Thermal response of optical reticles: experimental verification of finite element models

To extend optical lithography technology to the sub-65-nm linewidth regime, all mask-related distortions must be eliminated or minimized. Thermal distortion during the exposure process can be a significant contribution to the total pattern placement error budget for advanced photomasks. Consequently, several finite element (FE) models were developed to predict the thermal and mechanical response of an optical reticle during exposure. We present the experimental verification of the FE thermal models. In particular, the results of the numerical simulation are compared with the experimental data and excellent agreement is found.