Defect Inspection Wafer Notch Orientation and Defect Detection Dependency

Abstract

Defect detection and defect control are crucial for yield improvement in semiconductor industry. A discrepancy between detected defects compared to yield data regarding a common defect type was found. Historical data show a different behavior was seen on different product groups. A product design analysis on affected layer shows a striking difference in the Terminal Metal Layer (TML) line orientation between those product groups. A particle deposition system was used to distribute a fixed number of PSL spheres on to wafers prior etch process and defect inspections with different wafer notch orientations were performed at the final step. Those deposited PSL spheres prior etch process resulted in extra pattern defects at the inspection step. Extra pattern defects were mostly detected using a certain wafer notch orientation recipe to the majority of TML line orientation compared to the other one. This case study discusses the influence of a defect inspection wafer notch orientation to the defect capture rate on TML layer. Based on this result, the industry should consider the majority line orientation of respective layer on each inspection step when creating a new defect scanning recipe, especially for TML layer.