Sensitivity enhancement in OCD metrology by optimizing azimuth angle based on the RCWA simulation

Abstract

Monitoring process using optical critical dimension (OCD) metrology has been performed with a pre-fixed and unoptimized azimuth angle for all modules. Azimuth angle has a great influence on the optical sensitivity and can be easily tuned by changing the wafer rotation. In this study, we suggest the optimal azimuth angle for both FinFET and MOSFET device based on the rigorous coupled wave analysis (RCWA). For FinFET device, the optical sensitivity at the optimal angle was improved around 30% for two modules compared to that of pre-fixed angle. For MBCFET, we demonstrated that the simulated sensitivity is consistent with experiment and confirmed 10% sensitivity enhancement at 25 degree in experiment.