A study on noncontact characterization of silicon wafer subsurface

本研究的目的是发展新的非接触-无损的方法来表征硅片的亚表面性质，并建立我们已经提出的方法。提出了表面电位法、光导-频率响应法、电子束层析成像法等三种新方法，并提出了紫外/毫米波光电导衰减法和光电导振幅法等两种高灵敏度方法。表面电位法和光电导频响法对近表面区域在0.2微米深度有H+离子注入损伤的样品，以及PPCA法和UV/毫米波法都能很好地反映损伤情况。但是，仅对高剂量样品，表面电位法测得的结果与其他方法测得的结果不同。镜面抛光引起损伤的样品，表面电位法测得的抛光压力与损伤特性与PPCA法测得的结果一致。在CMP工艺中，当抛光压力为65g/cm2时，损伤最小。用表面电位法测量各种蚀刻方式引起的亚表面损伤程度，如湿HF蚀刻和等离子体蚀刻，与PPCA和光电导频率响应方法所获得的亚表面损伤程度相对应，从理论上认为是可能的。此外，还从理论上和实验上推导了紫外/毫米波（100 GHZ） PCD方法获得最大灵敏度的条件。

The purpose in this study is to newly develop noncontacting-nondistructing methods characterizing subsurface property in silicon wafers and to establish the methods already proposed by us. Three new methods as a surface potential method, a photoconductivity-frequency response method, an electron beam tomography have been proposed and already proposed two methods as an UV/millimeter-wave PCD (Photoconductivity decay) method and a PPCA (photoconductivity amplitude) method have been developed to be high sensitivity. The surface potential method and photoconductivity frequency response method for the sample having H+ ion implanted damage in near surface region in 0.2 micrometer depth well reflected the damage as well as both the PPCA and UV/millimeter-wave methods. But, for only high-dose sample, the result by only the surface potential method showed different behavior from one by other methods The polishing-pressure vs. damage characteristics measured using the surface potential method for the sample with mirror polishing induced damage is in a agreement with one with PPCA.The damage has been founded to be minimum at polishing pressure of 65g/cm2 in CMP process. The degree of damage measured by the surface potential method for the subsurface damage induced by various etching ways as wet HF etching and plasma etching corresponded with ones obtained by both the PPCA and photoconductivity frequency response methods Subsurface tomography using an electron beam has been theoretically considered to be possible. Moreover, the condition to obtain the maximum sensitivity in the UV/millimeter-wave (100 GHZ) PCD method has been deduced theoretically and experimentally.