An Overview on Wafer Pre-Aligner

Wafer pre-aligner plays an important role in wafer manufacture. Wafer pre-aligner positions wafers accurately before they are transferred onto exposure platform, and the positioning accuracy greatly affects the exposure accuracy of wafer and the work efficiency of the whole manufacture system. The paper makes an overview on wafer pre-aligner from the following aspects: working principle, mechanical structure, machine vision and the algorithm on the detection of wafer edge.