Patent ID: 7436513

Claim:
A wafer pre-alignment apparatus comprising: a wafer rotating member capable of rotating a disk-shaped wafer held on a table having a vertical rotating axis; a rotation detecting member for detecting a rotating position of the wafer rotating member and converting the rotating position detected into an electric signal; a light emitting member for emitting light toward the periphery of the wafer held by the wafer rotating member; a CCD linear sensor including a large number of pixels linearly arranged in a predetermined order, for reading out stored charges successively from the first pixel according to a transfer pulse signal and successively outputting stored charges of all the pixels as electric signals; a signal processing member for repeatedly detecting the edge positions of the wafer at a plurality of optional points over the outer periphery of the wafer when it receives a signal from the CCD linear sensor and a signal from the rotation detecting member and storing these edge positions thus detected in a memory, and acquiring at least one of an orientation-flat position, notch position and center position of the wafer on the basis of the edge positions detected; an up-down counter for counting signals received from the rotation detecting member; a measured angle setting register for storing angular value information which is obtained by dividing the number of counts during a single revolution by the rotation detecting member by the number of measurement points during the single rotation; and a comparator for comparing the angular value information set in the measured angle setting register and the counted value of the up-down counter, wherein the apparatus sequentially loads outer peripheral data corresponding to one round of the wafer without stopping the motor.