Strong correlation between de-protection induced thickness reduction and amplified chemical reaction in the
exposed area of the chemically amplified resist (CAR) during post-exposure bake (PEB) has been established.
The optical properties of the resist film due to the thickness reduction can be detected using a spectroscopic
ellipsometer. In this paper, a rotating polarizer spectroscopic ellipsometer is developed and a proposed control
scheme is presented for signature profiles matching. With the implementation of the control scheme, wafer-towafer
critical dimensions (CD) uniformity is improved by 5 times.
Current approaches to control critical dimensions (CD) uniformity during lithography is primarily based on run-to-
run (R2R) methods where the CD is measured at the end of the process and correction is done on the next
wafer (or batch of wafers) by adjusting the parameter set-points. In this work, we proposed a method to monitor the various photoresist parameters (e.g. photoresist thickness, photoactive compound) and CD in-situ and in real-time. Through modeling and real-time identification, we develop new in-situ measurement techniques for the various parameters of interest in the lithography sequence using existing available data in the manufacturing process.