Analysis of Coulomb and Johnsen-Rahbek electrostatic chuck performance in the presence of particles for extreme ultraviolet lithography

Abstract

The successful implementation of extreme ultraviolet lithography (EUVL) requires the use of an electrostatic chuck to both support and flatten the mask during scanning exposure. The EUVL Mask Standard, SEMI P37, specifies the nonflatness of the mask frontside and backside, as well as the thickness variation, to be 30 to 100 nm peak-to-valley, dependent on the class of substrate. Thus, characterizing and predicting the capability of the electrostatic chuck to reduce mask nonflatness to meet these specifications are critical issues. In this research, the ability of such chucks to deal with the presence of particles trapped between the substrate and chuck is investigated. Analytical and finite element modeling are used to identify the forces needed to fully embed or deform a particle during electrostatic chucking. Simulation results (using an elastic analysis) show that the forces generated by both Coulomb and Johnsen-Rahbek chucks should be able to sufficiently deform, or flatten, particles that are nearly 1.0 µm in size.