Examination of the effects of high-density plasmas on the surface of HgCdTe

Benson

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

Benson

Smith

2009

Self Cite

“…11,29,[30][31][32] Although these combinations were not optimized, the best results were obtained by etching the InSb (112)B wafer with lactic acid:nitric acid (10:1) (it should be noted that in this case the lactic acid: HNO 3 :HF at 25:4:1 etch was not included), then exposing the wafer to an H + /Ar + plasma 26,33 followed by annealing at 375°C under Sb flux. Figure 1 shows the RHEED pattern of an InSb (112)B substrate thus prepared.…”

Section: Growth Of Cdte On Insbmentioning

confidence: 99%

“…This twostep process yielded an oxide and contaminant-free, nearly stoichiometric surface. Low-energy (slightly above the sputter threshold), inert He + light-ion exposure reduces sputter rates 33,43,44 and minimizes chemical effects (such as hydrogen plasma depletion of Sb 37,44,45 ) and structural damage associated with H + /Ar + plasmas and Ar + ion beam sputtering. 37,[44][45][46][47] The He + plasma is particularly beneficial because of its shallow penetration depth.…”

Section: He + Plasma Cleaning Of Insb By Icpmentioning

confidence: 99%

Plasma-Cleaned InSb (112)B for Large-Area Epitaxy of HgCdTe Sensors

Jaime-Vasquez

Martinka

et al. 2008

Self Cite

Plasma etching of (112)B InSb to prepare this semiconductor for the heteroepitaxy deposition of CdTe and initial studies of CdTe epilayers grown by molecular beam epitaxy (MBE) on InSb (112)B substrates cleaned with various plasma treatments are presented. X-ray diffraction rocking curve maps of the MBE CdTe epilayers on 3-inch InSb (112)B substrates have full-width at half-maxima (FWHM) values in the range of 20 arcsec to 30 arcsec. An etch pit density analysis of the 3-inch CdTe epilayers reveals a defect density of 1.0 · 10 7 cm -2 and 7.7 · 10 5 cm -2 at the center and edge of the wafer, respectively. Evaluation of a standard HgCdTe annealing process suggests that the removal of the InSb substrate is likely to be needed prior to any postgrowth annealing in Hg overpressure. Finally, we present a low-energy helium plasma exposure of wet-etched InSb (112)B substrates that provides a uniform epi-ready surface that is nearly stoichiometric, and free of oxide and residual contaminants.

“…[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

Benson

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.