Enhanced temperature uniformity of electrostatic chuck: ceramic surface contact ratio and backside gas pressure

Abstract

In semiconductor processes, precise control of the wafer-in-process is a key parameter closely related to production yield, and the development of electrostatic chuck (ESC) continues towards higher chucking voltage with higher backside cooling gas. This study aims to determine the target temperature and uniformity of the wafer surface by varying the contact ratio of the ceramic-embossing facing the wafer-in-process. A computational fluid dynamics model with a thin wall boundary condition is considered to interpret the flow of the rarefied gas between the wafer and ceramic surface of the ESC. Through 3D simulations conducted with ANSYS Fluent, we observed temperature changes as the backside gas pressure varied from 1 to 9 Torr. The ESC with the highest contact ratio performed exceptionally well with an average temperature of 295 K and a coefficient of variation of 0.04%.