Wafermap-Designs Based on Zernike Polynomials

In Semiconductor industries, homogeneity of the results of many process steps across the wafer is an essential goal and tightly correlated with the final yield. It is important to make a judgement of homogeneity based on a sample of points that is efficient: Typical deviation from “flatness” have to be detected with an affordable (i. e. small) number of test points on the wafer.

Easy to interpret deviations from flatness can be described by Zernike polynomials which are state of the art in describing optical deficiencies in the human eye or in adaptive optics. This report describes Zernike Polynomials and shows how the measuring points are optimally placed on the wafer surface using the statistical software Cornerstone.