Development of a high-selectivity process for electron cyclotron resonance plasma etching of II-VI semiconductors

Smith

2009

Self Cite

Inductively coupled plasmas (ICP) are the high-density plasmas of choice for the processing of HgCdTe and related compounds. Most dry plasma process works have been performed on HgCdTe for pixel delineation and the p-to-ntype conversion of HgCdTe. We would like to use the advantages of ''dry'' plasma processing to perform passivation etching of HgCdTe. Plasma processing promises the ability to create small vias, 2 lm or less with excellent uniformity across a wafer, good run-to-run uniformity, and good etch rate control. In this study we developed processes to controllably etch CdTe, the most common passivation material used for photovoltaic-based HgCdTe devices. We created a process based on xenon gas that allows for the slow controllable CdTe etch at only 0.035 lm/min, with smooth morphology and rounded corners to promote further processing.

Section: Discussion and Resultsmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] However, ICP plasma processing, used in HgCdTe, is still maturing and continued research is needed. 4,7,14 ICP plasma processing may also be used to replace conventional wet chemical clean-up, and even be used in the surface preparation for epitaxy of II-VI materials.…”

Section: Introductionmentioning

confidence: 99%

Plasma Passivation Etching for HgCdTe

Smith

2009

Self Cite

“…5,10,11 Argon to hydrogen gas ratio of 4:1 with a DC bias input power of 60 W was used for these studies. The average ion energy has been previously determined to be Ϸ15 eV for these plasma conditions.…”

Section: Methodsmentioning

confidence: 99%

Surface structure of plasma-etched (211)B HgCdTe

Varesi

et al. 2005

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The surface of (211)B HgCdTe has been studied by reflection high-energy electron diffraction (RHEED) and atomic force microscopy (AFM). RHEED analysis of the as-grown Hg-rich molecular beam epitaxy (MBE) (211)B HgCdTe suggests the surface reconstructs by additional Hg incorporation. The plasma-etched (211)B HgCdTe surface is crystalline but stepped and facetted. RHEED analysis indicates asymmetric pyramids (base dimensions Ϸ 0.5 ϫ 1.1 nm) are formed to minimize surface Hg concentration. The AFM examination of plasma-etched (211)B HgCdTe reveals oriented mesoscopic features.

“…[1][2][3][4] Several studies have also reported the effect that high-density ''dry'' electron cyclotron resonance (ECR) plasmas have on HgCdTe epitaxial properties. [5][6][7][8][9][10][11][12][13][14] However, ICP plasma processing, for use in HgCdTe, is still maturing and continued research is needed. 4,7,14,15 ICP plasma processing may also be used to replace conventional wet chemical clean-up, and can even be used in the surface preparation for epitaxy of II-VI materials.…”

Section: Introductionmentioning

confidence: 99%

Morphology of Inductively Coupled Plasma Processed HgCdTe Surfaces

Smith

2008

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.