Versatile masking process for plasma etched backside via holes in GaAs

摘要

We have developed a versatile backside via patterning process for a visible transmission modulator application. The vias are processed on mechanically thinned (approximately)100 (mu)m thick GaAs using a (approximately)45 (mu)m thick, negative tone, photo definable Polyimide mask and RIE plasma etching. The Polyimide masking process was found to be superior in both etch resistance and ease of use (more robust process, thicker, straighter sidewall Profile films,were more easily attained) to masking with standard optical photoresist. With the improved etch resistance (GaAs-to-polyimide etch selectivities > 10:1) we were able to Optimize Cl(sub 2)-based plasma chemistries and etching conditions to achieve high GaAs etch rates in the RIE exceeding 5.0 (mu)m/min. These etch optimization results along with our novel via patterning process are reported in this paper. (ERA citation 19:033954)