Adapting Electrostatic Chucks for Dry Etching of GaAs
David Tossell, Kevin Powell, Michele Bourke, Yiping Song
Etch Group, Trikon Technologies Ltd.
Ringland Way, Newport NP62TA, UK
Within the silicon industry an electrostatic chuck (ESC) used with helium backside cooling has become the primary method for controlling wafer temperature during plasma etch processing. An ESC has several advantages over mechanical clamping namely: no wafer frontside contact; lower particulate levels; simpler; low cost; higher reliability. However, when applied to GaAs (and other III-V materials), it has been found that ESCs that work well for Si can manifest a number of problems. This paper describes the adaptation of a thick dielectric capacitive ESC, widely used for Si etching in production to GaAs processes. Methods for reducing and/or eliminating the undesirable effects seen for GaAs etching are described, along with example process results. Possible reasons for the differences between Si and GaAs processing are discussed. It also details how the thick dielectric approach allows for the processing of wafers on sapphire carriers and results for a GaAs backside etch are presented. Finally, a further adaptation of the same thick dielectric ESC technology to InP processing is presented.