A study on noncontact characterization of silicon wafer subsurface

本研究的目的是发展一种新的非接触非破坏性表征硅片亚表面性质的方法，并建立我们已经提出的方法。已经提出了三种新的方法，如表面电位法、光电导-频率响应法、电子束层析成像法，并且已经提出了两种方法，如UV/毫米波PCD（光电导衰减）法和PPCA（光电导振幅）法，已经开发为高灵敏度。表面电位法和光电导频率响应法以及PPCA法和紫外/毫米波法都能很好地反映出近表面0.2 μ m深度H+离子注入损伤的样品的损伤情况。但是，对于高剂量的样品，表面电位法的结果与其它方法的结果不同。对于镜面抛光损伤的样品，表面电位法测量的抛光压力-损伤特性与PPCA法测量的抛光压力-损伤特性基本一致，发现CMP过程中在抛光压力为65 g/cm ~ 2时损伤最小。由表面电位法测量的损伤程度的各种蚀刻方式，如湿法HF蚀刻和等离子体蚀刻引起的亚表面损伤对应于由PPCA和光电导频率响应方法获得的亚表面层析成像，使用电子束已在理论上被认为是可能的。从理论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.