Automatic 3D-Laser Scattering Measurement for Ultra-Finished Surface with Nanowatt Sensitivity
Taeho Ha, Keiichi Kimura, Takashi Miyoshi, and Yasuhiro Takaya
Department of Mechanical Engineering and Systems, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
Automatic measurement system that can evaluate laser scattering from an ultra-finished surface has been developed. The system uses Ar+ laser as an illumination source, and a highly sensitive photomultiplier tube (PMT) for detecting scattered light. The major feature of the developed system is that the 3-dimensional distribution of scattered light from a scatterer is obtained by rotating the detector using two motor-driven rotation stages. The feasibility of this system is demonstrated by measuring light scattered from oxide silicon surfaces containing a microscratch and polystyrene latex (PSL) sphere. Experimental results show that the spatial scattering light intensity pattern can be obtained with nanowatt sensitivity, and shows that scattered light patterns for each scatterer are distinctive. This measurement system is thus expected to become an effective tool to characterize ultra-finished surfaces, such as a post-chemical mechanical polishing (CMP) wafer surface, from the pattern of detected scattered light intensity.
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