Robust Real-Time Thin Film Thickness Estimation

The dissolution of photoresist in developer solution often leads to changes in the chemical composite of the solution which hinder film thickness estimation. This paper addresses this issue by proposing a modified fringe order computation (MFOC) method which analyses reflected light intensity data acquired using commercially available optical spectrometry system. MFOC uses simple arithmetic operations and is capable of computing film thickness at real-time. It is more reliable as compared to other methods during develop step in microlithography process