DETECTION OF WAFER POSITION

摘要

PURPOSE:To provide a method for detecting the position of a wafer which is not dependent on the eccentricity state of the wafer and is hardly be susceptible to a size error of the wafer. CONSTITUTION:An edge distance 'r' which corresponds to a change in a distance between the center of rotation of a wafer and an edge of the wafer is detected as a data series. Based on the detected data series of the edge distance 'r', an eccentric vector (eccentricity 'd', eccentricity vectorial angle phi which corresponds to the deviation in position between the center of the wafer and the center of rotation is determined. A higher-order polynomial curve is fit to a data series of the edge distance 'r' for parts of the wafer edge which are out of an orientation flat range (A1-QS, QF-A1) and thereby an approximate curve is found and then the eccentricity vector is determined based on the approximate curve. By this method, the eccentiricity of the wafer can be found regardless whether a maximum value (M2) or a minimum value (M1) of the edge distance 'r' for parts out of the orientation range is concealed by the orientation flat.