Design of an active wafer table for wafer scanners

This project focusses on the design of an active wafer table for future ASML Wafer Scanners. Contrary to passive wafer tables, the active wafer table will (partially) support the wafer by small actuators. Each supporting actuator has the ability to deform the wafer out-of-plane, providing means to improve focus, overlay, throughput, and the wafer table’s durability.

PhD Candidate: Micha Steur
Promotor: M. Steinbuch
Supervisor: P.C.J.N. Rosielle (TU/e), W. Aangenent (ASML RE Mechatronics), H. Vermeulen (ASML RE Mechatronics & TU/e)
Project Funding: This project is funded by ASML
Project Period: January 2013 – January 2017

The main focus and overlay issues appear at the edge of the wafer, consequently this will be the region where the active wafer table can contribute the most to future ASML Wafer Scanners. The basic principle is similar to that of adaptive optics, in this case deforming the wafer to counteract any aberrations and expose the desired image as well as possible on the dies.

Due to increased wear and chemical mechanical processes, the edge region’s focus and overlay vary greatly throughout the layers exposures. The active wafer table will therefore have to take all error sources into account, to maintain an overall high accuracy at each exposed layer under the extreme dynamics during scanning.