Abstract: In view of the new requirements of manufacturing equipment for large-size wafer of 300 mm diameter and 90 nm process, a method of edge information collecting and processing is proposed, based on which the vision system of pre-alignment robot is established. By the help of de-noising using compromise of wavelet coefficient, the method which synthesizes least square regression and weighted means, can successfully realize the conversion from CCD signal to position data through calibration, filtering, analysis and synthesis of light information, and the problem of wafer edge detection and location is resolved. The result measurement test of repetitive positioning accuracy shows that the robot can carry out the detection and alignment of wafer pinpoint, attain the precision requirement and promote the working performance of whole pre-alignment system.

Key words: Calibration of pinpoints, Data processing, Position correction, Pre-alignment, Vision system