In-situ measurement and control of photoresist processing in lithography

Abstract

Lithography is the key enabling technology in semiconductor manufacturing. The economic feasibility of all future lithography techniques will depend on the satisfaction of increasingly stringent error tolerances in Critical Dimension (CD) uniformity across the wafer. In this work, in-situ measurement and real-time control are used in lithography to control some factors that can cause CD variation. Based on first principle modeling, an in-situ approach is developed to detect wafer warpage from integrated temperature measurement of a single-zone thermal processing system. Extension to estimate wafer warpage profile is achieved by using a programmable multi-zone thermal processing system. Furthermore, real-time control of steady-state wafer temperature uniformity is achieved by using the multi-zone system. A real-time control strategy is also implemented for a deep ultra-violet photoresist development process. With in-situ resist thickness estimation, a 6 times improvement in development end-time uniformity is achieved by manipulating the development temperature distribution through an integrated bake/chill system.