| 摘要 |
PURPOSE:To correct the position of a stage by irradiating a wafer on the stage by a luminous element through a mask and calculating an OFF position based on electric signals corresponding to the difference in intensity of the reflected lights from the stage, wafer, and mask so as to move the stage. CONSTITUTION:Light emission of a LED 53 is controlled by a control circuit 57 including a calculator and a wafer 33 on a stage 41 is irradiated through a mask 49 having a mark 51. The reflected lights from the stage 41, wafer 33, and mark 51 on the mask are detected by a CCD 55 which converts them into electric signals and sends them to the control circuit 57. As the intensity of the reflected light from the mark 51 is different from that from the stage or wafer, a circuit 27 determines the position of the mark 51 based on an electric signal corresponding to the difference in intensity. Also, the reflected light intensity of the wafer is different from that of the stage and the OFF position can be determined based on an electric signal corresponding to the intensity difference. The control circuit drives pulse motors 43 and 45 to set the wafer at the optimum position. |
