Optimization of dry etch process conditions for HgCdTe detector arrays

Sperry

et al. 2005

We report on the physical attributes of an argon-hydrogen plasma and the effects that induced changes in these attributes have on the physical and electrical characteristics of the plasma itself. Changes in the plasma conditions of these argon-hydrogen plasmas due to variations in microwave power, DC biasing, gas concentrations, and pressures were measured. We determined that increasing the hydrogen flow increases the sheath potential of the plasma, thereby increasing the arrival energy of ions at the surface of a sample placed in the plasma. Even with the decrease in plasma density from an increase in hydrogen input flow, we found the ion current is maintained in the predominately hydrogen plasma and is likely compensated by the high velocity and long mean free path of the hydrogen. We also observed that increasing total pressure also results in hydrogen ions dominating the total number of ions reaching the Langmuir probe and therefore the sample during processing. Last, a model based on the ion/electron energy ratio was developed and used to determine the relative ion concentrations of hydrogen and argon ions.

Section: Hydrogen Percent Variationsmentioning

confidence: 83%

“…[1][2][3][4][5][6][7][8] The effects on the material induced by changes in the process chemistry have been well documented. 7,8 Little is known of the effects induced within the argon-hydrogen plasma itself by changes in the various process parameters associated with the operation of the reactor.…”

Section: Introductionmentioning

confidence: 99%

A langmuir probe investigation of electron cyclotron resonance argon-hydrogen plasmas

Sperry

et al. 2005

“…[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

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.

“…[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.…”

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.