Simultaneous Measurement of Size and Depth of Each Defect in a Silicon Wafer Using Light Scattering at Two Wavelengths: Principle, Limitation and Applications of Optical Shallow Defect Analyzer

To inspect the quality of the silicon wafer surface region where devices are to be fabricated, an instrument termed optical shallow defect analyzer (OSDA) was developed [Takeda et al. .: Mater. Res. Soc. Symp. Proc. 442 (1997) 37]. The OSDA can measure the size and depth of a defect by measuring light scattered from the defect at two wavelengths having different penetration depths in Si. In this paper, we describe the validity and the limitation of the method by using a two-dimensional distribution analysis of the signal intensities. This analysis clarifies that the detectable defect depth depends on the defect size. The smaller the defect size is, the shallower the detectable depth range is. As an application of the OSDA, crystal originated particles (COPs) induced by thermal oxidation of Czochralski silicon (CZ-Si) are analyzed. The COPs and the inner defects are resolved by measurement using OSDA. The COPs are measured as the defects whose depths are about zero, whose sizes are larger than grown-in defects, and whose density increases with thermal oxidation.