Patent ID: 8600150

Claim:
A wafer aligning apparatus comprising: a transfer robot that transfers a wafer; a laser sensor that generates a trigger signal when the transfer robot transfers the wafer from a cassette disposed in a load lock chamber to a transfer chamber, wherein the trigger signal is generated in response to a change in reflected light detected by the laser sensor when a boundary between a blade of the transfer robot and a coupler of the transfer robot passes under the laser sensor; a Charge-Coupled Device (CCD) camera that takes an image of the wafer while disposed on the transfer robot in accordance with the trigger signal and then converts the image into digital signals; a signal processing unit that calculates a center alignment correction value for the wafer by comparing the digital signals to a master image stored in the signal processing unit; and a robot controller that receives the center alignment correction value from the signal processing unit and controls movement of the transfer robot in accordance with the center alignment correction value, wherein during calculation of the center alignment correction value the signal processing unit is configured to calculate a wafer angle difference between respective wafer angles of the wafer image and the master image by comparing the digital signals with the master image, and compare a wafer center difference to a first, the signal processing unit being further configured, when the wafer center difference exceeds the first limit and the wafer angle difference exceeds a second limit, to transfer the wafer using the transfer robot to an aligning chamber, and after aligning of the wafer transferring the wafer to the process chamber, and the signal processing unit being further configured, when the wafer center difference does not exceed the first limit and the wafer angle difference does not exceed the second limit, to calculate the center alignment correction value in accordance with a calculated wafer center difference.