Abstract
Laser dark field inspection tools for LSI wafer patterns are very fast and often used in LSI fabrications. However with non-repetitive LSI patterns, the sensitivity of the conventional die-to-die inspection method is not sufficient due to the increase in noise that occurs in connection with highly coherent laser illumination and the variation of the thin film thickness of the LSI patterns. In this paper two methods are combined for highly sensitive image comparison : self-reference comparison and die-to-golden die comparison. The self-reference comparison searches for parts of similar patterns in each die and the die-to-golden die comparison generates images with similar patterns on the basis of adjacent dies. The combined methods adaptively select the parts to be referenced pixel by pixel. Experimental results showed they could successfully detect a low S/N defect signal of 0.12 in the non-repetitive patterns.
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