| 摘要 |
PURPOSE: A wafer cassette lift installed in a local processing port of a stepper is provided to prevent damage of a wafer due to the impact between the wafer and a wafer transfer arm by sensing exactly a loading state of the wafer using light emitting and receiving devices. CONSTITUTION: A wafer cassette lift includes a lift plate(120), a controlling part(160), a lift driving part, a frame(140) with an opening portion(141) and a sensing part(150). The lift plate moves a wafer cassette(1) up and down. The controlling part controls the lift driving part for driving the lift plate. The sensing part is installed on an inner surface of the opening portion to detect wafers(w) of the wafer cassette. The sensing part includes the first and second sensing part. The first and second sensing part are spaced apart from each other. The first sensing part includes the first light emitting and receiving device(151,153). The second sensing part includes the second light emitting and receiving device(152,154).
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