CdZnTe晶片4种化学钝化工艺效果的比较

Comparison of Four Chemical Passivation Technologies for CdZnTe Wafer

常用于X射线和γ射线探测器中的CdZnTe(CZT)晶片经机械抛光后表面存在损伤层和许多肉眼看不到的划痕,采用溴甲醇(Br2-CH3OH)腐蚀可有效去除损伤层和划痕,使表面变得光亮平整。但经Br2-CH3OH腐蚀的表面富Te而产生较大的表面漏电流,为此,采用H2O2溶液,NH4F/H2O2溶液,KOH-KCl溶液+NH4F/H2O2溶液二步法和溴水4种湿法化学钝化工艺,对CZT晶片表面进行了钝化处理,并对比了其钝化效果。结果表明:二步法钝化效果最好,表面漏电流降低4个数量级,NH4F/H2O2对CZT晶片表面的钝化效果较好,表面漏电流降低3个数量级。

CdZnTe (CZT) wafers commonly used in X-ray and γ-ray detectors are liable to surface damage and scratching invisible with naked eyes during mechanical polishing. The damaged layers and scratches can be effectively removed by using Br2-CH3OH to corrode generating bright and smooth surface. However,CZT wafers corroded with Br2-CH3OH have a large surface leakage current due to Te-enrichment on the corroded surface. Therefore,CZT wafers were chemically passivated with H2O2 solution,NH4F/H2O2 solution,KOH-KCl solution plus NH4F/H2O2 solution (two-step passivation) and bromine solution respectively. The passivation effectiveness of the four kinds of solutions was compared. Results indicate that the two-step passivation is the most effective for passivation of the CZT wafers,and the surface leakage current can be reduced by four orders of magnitude,while the NH4F/H2O2 solution is next to the best in terms of passivation of the CZT wafers,and in this case the surface leakage current can be reduced by three orders of magnitude.