Morphology of Inductively Coupled Plasma Processed HgCdTe Surfaces

Abstract

Inductively coupled plasma (ICP) processing has become the industrial processing standard for HgCdTe and its related II-VI compounds. In this study ICP processes were developed that allow several microns of HgCdTe to be plasma etched while maintaining a low root-mean-square (RMS) roughness, and even improving the surface roughness in the case of HgCdTe-on-Si. These ICP processes are superior to older electron cyclotron resonance (ECR) plasma etches. The resulting ICP plasma processed surfaces are oxygen and carbon free, have a good reflection high-energy electron diffraction (RHEED) pattern, and have only a small amount of mercury depletion, x = 0.22 to 0.47 (where x is the ratio of Cd to Hg), in the first 25 Å to 30 Å of the HgCdTe. Nanofeatures of the as-grown HgCdTe are retained during the process and are believed to be indicative of the fundamental defect mechanisms in the different HgCdTe etched surfaces. Results from these experiments strongly suggest that ICP plasma processes can be used to delineate pixels, etch vias, clean surfaces, and even produce epi-ready surfaces that would allow HgCdTe to become much more manufacturable, and perhaps allow the replacement of wet processing in HgCdTe.

Dry etched SiO2 Mask for HgCdTe Etching Process

“…As a result, if the SiO 2 is <500 nm, a corner-preferred plasma etching will ruin the profile of the mask during a long time etching. This nonuniform electron-attraction model may differ a little with that for photoresist mask, 16,27,31 where the Ar + can penetrate into the photoresist and become a dominant factor. Interestingly, although the profile of SiO 2 mask has deteriorated completely in Fig.…”

Low-Roughness Plasma Etching of HgCdTe Masked with Patterned Silicon Dioxide

“…1,2 Several groups have reported the impact of high-density ''dry'' electron cyclotron resonance (ECR) plasma or inductively coupled plasma (ICP)-enhanced reactive ion etching (RIE) processes on HgCdTe epitaxial properties. 3,4 Two-color HgCdTe IRFPAs devices were also achieved by applying ICP etching to form single mesa pixels. 5,6 In most reported studies and device fabrications, patterned thick photoresist (PR) films formed using a standard photolithography process are employed as a mask to etch HgCdTe material.…”