Automated Wafer Analysis using Wafer Map Autocorrelation

A complete wafer map contains information sufficient to discriminate certain prober errors, parametric errors, and point defect errors even without the full measured data set. Autocorrelation of the wafer map allows a simple automated analysis system to provide immediate feedback to the operator of known errors, allowing immediate retest in case of wafer probing errors and providing information to process engineers about possible manufacturing errors. The author provides a description of an algorithm which has proven useful in increasing measured yield and differentiating point defect errors from more traditional process errors.