Effects of Chemomechanical Polishing on CdZnTe X-ray and Gamma-Ray Detectors
Effects of Chemomechanical Polishing on CdZnTe X-ray and Gamma-Ray Detectors
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DOI：
10.1007/s11664-015-3881-7
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发表时间：
2015-06
影响因子：
2.1
通讯作者：
S. Egarievwe;A. Hossain;I. Okwechime;R. Gul;R. James
中科院分区：
文献类型：
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作者：
S. Egarievwe;A. Hossain;I. Okwechime;R. Gul;R. James
机械抛光用于x射线和伽玛射线探测器的碲化镉锌（CdZnTe）晶圆通常不足以去除因从铸锭上切割而造成的表面缺陷。制造引起的缺陷，如表面粗糙度、悬空键和非化学计量表面，通常通过抛光和蚀刻表面来减少。在我们早期的氧化铝粉机械抛光、溴化氢在双氧水溶液中蚀刻以及溴-甲醇-乙二醇溶液化学机械抛光的研究中，我们发现化学机械抛光过程产生的表面泄漏电流最小。在这项研究中，我们重点研究了在机械抛光后使用两种化学物质对CdZnTe晶圆进行化学机械抛光，即溴-甲醇-乙二醇（BME）溶液和溴化氢（HBr）在过氧化氢和乙二醇溶液中。我们使用x射线光电子能谱（XPS）、电流-电压（I-V）测量和Am-241光谱响应测量来表征和比较每种溶液的效果。结果表明，基于hbr的溶液比BME溶液产生更低的泄漏电流。在两个样品上使用相同的化学机械抛光溶液的结果证实，表面处理影响测量的体电流（体电流和表面电流的组合）。XPS结果表明，与hbr溶液相比，BME溶液在机械抛光过程中显著降低了氧化碲与碲的峰比（Te 3d5/ 2o2为78.9%，Te 3d3/2O2为76.7%），而hbr溶液则分别为27.6%和35.8%。光谱响应测量结果表明，三种CdZnTe样品的Am-241的59.5 kev峰保持在相同的通道数下。虽然基于bme的溶液具有7.15%的半最大全宽（FWHM），而基于hbr的溶液具有7.59%的半最大全宽（FWHM），但后者在7天内的性能变化较小，为0.39%，而基于bme的溶液为0.69%。
Mechanically polishing cadmium zinc telluride (CdZnTe) wafers for x-ray and gamma-ray detectors often is inadequate in removing surface defects caused by cutting them from the ingots. Fabrication-induced defects, such as surface roughness, dangling bonds, and nonstoichiometric surfaces, often are reduced through polishing and etching the surface. In our earlier studies of mechanical polishing with alumina powder, etching with hydrogen bromide in hydrogen peroxide solution, and chemomechanical polishing with bromine–methanol–ethylene glycol solution, we found that the chemomechanical polishing process produced the least surface leakage current. In this research, we focused on using two chemicals to chemomechanically polish CdZnTe wafers after mechanical polishing, viz. bromine–methanol–ethylene glycol (BME) solution, and hydrogen bromide (HBr) in a hydrogen peroxide and ethylene–glycol solution. We used x-ray photoelectron spectroscopy (XPS), current–voltage (I–V) measurements, and Am-241 spectral response measurements to characterize and compare the effects of each solution. The results show that the HBr-based solution produced lower leakage current than the BME solution. Results from using the same chemomechanical polishing solution on two samples confirmed that the surface treatment affects the measured bulk current (a combination of bulk and surface currents). XPS results indicate that the tellurium oxide to tellurium peak ratios for the mechanical polishing process were reduced significantly by chemomechanical polishing using the BME solution (78.9% for Te 3d5/2O2and 76.7% for Te 3d3/2O2) compared with the HBr-based solution (27.6% for Te 3d5/2O2and 35.8% for Te 3d3/2O2). Spectral response measurements showed that the 59.5-keV peak of Am-241 remained under the same channel number for all three CdZnTe samples. While the BME-based solution gave a better performance of 7.15% full-width at half-maximum (FWHM) compared with 7.59% FWHM for the HBr-based solution, the latter showed a smaller variation in performance of 0.39% FWHM over 7 days compared with 0.69% for the BME-based solution.