| 摘要 |
PURPOSE:To make it possible to detect the accurate position of a work, such as wafer, etc., placed on a chuck by using the signals or indications of a detecting means to detect the degree of vacuum of grooves or holes formed on the adsorption section of a chuck body. CONSTITUTION:An extreme outer adsorption groove 2d is on a little inner side of a wafer 3 in the form following the external shape of the wafer 3, and is evacuated through a pipe line 5 by a vacuum pump independently of other adsorption grooves 2a, 2b, 2c; therefore, when the wafer 3 is not placed correctly on a wafer chuck body 1, the adsorption area of the adsorption groove 2d is not all covered by the wafer 3, and air flows slightly into this groove 2d, changing the degree of vacuum. The change in the degree of vacuum is detected by a vacuum gauge 4 and the positional slippage of the wafer is found. When this slippage is found, the evacuation pumping is stopped and the wafer 3 is replaced rightly on the wafer chuck 1, and then the vacuum pumping is started again. |
