複数の評価関数を用いたロバストなLSIパターンの位置合わせ方法

概要

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This paper reports an image-processing algorithm for robust inspection of LSI wafer patterns using SEM. In order to detect defects in a regular LSI pattern, a pair of long patterns is compared, blocked images are aligned, and defects are judged using the aligned images. The LSI wafer pattern is defined to consist of blank space, fine repetitive patterns, and unique patterns. Distortion of the SEM image is larger than the repetitive pattern pitch, requiring the system to keep track of the alignment in areas without pattern and to mitigate the indeterminacy of repetitive patterns. To satisfy these requirements, we suggest algorithm focused on consistency among local registration. Registration candidates in each block are calculated and a chain of the correct registration sequence, using candidate information in all the related blocks. To increase robustness, combination of two evaluation functions is proposed. Two-dimensional correlation and low pass filtered one-dimensional correlation are used. The latter is complement of the former from the perspective of finding fine repetitive pattern edge to ease finding correct route. Experimental evaluations confirm that most pattern cases can be inspected correctly using the proposed SEM inspection system.
社団法人電気学会の論文
2004-03-01