Automatic in-line to end-of-line defect correlation using FSRAM test structure for quick killer defect identification

This paper describes the use of Fast Static RAM (FSRAM) test structures to identify defect locations which are then used to wafer map defect sites. It describes how to automate in-line to end-of-line defect correlation to quickly identify the origin of killer defects. In-line defects are identified using a Tencor Surfscan 7000 and these defect locations are overlayed onto failing bitmap data from functional testers. The analysis and overlay software has been written using a commonly available database, RS/1 to automatically generate histograms of defects-to-fail ratios for each monitoring stage. This rapidly identifies the key defectivity steps in a new process. Using this approach large amounts of data can be quickly processed allowing realistic SPC defectivity limits to be set from a large sample size