Investigations on a Multiple Mask Technique to Depress Processing-Induced Damage of ICP-Etched HgCdTe Trenches

Abstract

A multiple mask technique, integrating patterned silicon dioxide (SiO₂) film over patterned thick photoresist (PR) film, has been investigated as a method to perform mesa etching for device delineation and electrical isolation of mercury cadmium telluride (HgCdTe) third-generation infrared focal-plane arrays. The multiple mask technique was achieved by standard thick PR photolithography, SiO₂ film deposition to cover the thick PR patterned film, and etching the SiO₂ film at the bottom region after another photolithography process. The dynamic resistance in the zero-bias and low-reverse-bias regions of HgCdTe photodiode arrays isolated by inductively coupled plasma (ICP) etching with the multiple mask of patterned SiO₂ and patterned thick PR film underneath was improved one- to twofold compared with a simple mask of patterned SiO₂. It is suggested that the multiple mask technique is capable of maintaining high etching selectivity while reducing the side-wall processing-induced damage of ICP-etched HgCdTe trenches. The results show that the multiple mask technique is readily available and shows great promise for etching HgCdTe mesa arrays.