Patent ID: 6374149
Filing Date: 2002-04-16
Classification: H01L,Y10S

Abstract:
A method for determining the center of a semiconductor wafer on a wafer table relative to a predetermined fixed location on said wafer table for accurate positioning and control of a robot arm, the method comprising the steps of:providing a wafer table movable in an x-y plane of a Cartesian coordinate system and having a semiconductor wafer disposed thereon; providing a sensing device for measuring geometrical data of said semiconductor wafer disposed on said wafer table; measuring geometrical data of said wafer disposed on said wafer table with said sensing device in the Cartesian coordinate system of said wafer table; providing a wafer center computing system containing data relative to said predetermined fixed location on said wafer table; receiving the measured geometrical data of said wafer at said wafer center computing system; computing in the Cartesian coordinate system of said wafer table the coordinates of said wafer center from said predetermined fixed location and said measured geometrical data of said wafer and the offset between a predetermined location on said wafer and said predetermined fixed location on said wafer table; and controlling a robot arm in response to said offset.