Microdisplay wafer-flatness metrology by optical interferometry

摘要

We report a microdisplay wafer-flatness metrology technique based on digital high-pass filtering of topography data obtained from a commercial optical interferometer. This technique dis- criminates against both wafer-scale bow/warp and pixel-scale roughness to reveal die-scale flatness variations that are the most relevant to microdisplay gap uniformity. We report flatness measurements of a variety of live and test silicon wafers supporting VLSI microdisplay circuitry, and show how these measurements correlate with the performance of liquid-microdisplays assembled from similar wafers.