This case study shows that wafer notch orientation can have a significant effect on defect capture rates obtained during defect inspection. The discovery was made when a review of historical data showed that the relationship between defect densities and yield varied greatly for different products in regard to a terminal metal layer. A product design analysis on the affected layer revealed that a majority of metal lines were oriented the vertical direction in one product and in the horizontal direction in the other. It was then shown that this difference could be offset by rotating the wafer in the defect scan tool, which resolved the data discrepancy. This work highlights the importance of considering the orientation of metal lines in each layer when creating a new defect scanning recipe.

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