Method for real-time critical dimensions signature monitoring and control: sensor, actuator, and experimental results

We present in this paper a system and method for real-time monitoring and control of critical dimensions (CD) signature profile in lithography. The proposed system involves the development and integration of a scatterometry system, a programmable multi-zone thermal processing system, and control system software. Based on scatterometry, the intensity and phase of the reflected light from the resist film are measured at a fixed incident angle and across multiple wavelengths. A programmable thermal processing system is then used to adjust the processing temperature during post-exposure baking in lithography to achieve the desired CD signature profile. Experimental results demonstrate the feasibility of the proposed approach. An improvement of CD signature control of 85% is achieved in terms of the mean square error with and without control.