| 摘要 |
In this step and repeat wafer direct exposure system, the initial reticle contains an alignment target which is repetitively exposed onto the semiconductor wafer at each circuit image location. Each subsequently used reticle contains a complementary shaped alignment pattern. At each array location, a low intensity light source is used for through-the-camera-lens alignment. Viewing optics and a video camera are used simultaneously to view the virtual image of the alignment target situated on the wafer and the corresponding alignment pattern situated on the reticle. While viewing, the stage is moved to achieve perfect alignment, after which the circuit pattern is exposed from the reticle onto the wafer. The wafer then is stepped and the process repeated at other array positions. The apparatus includes an air gauge system for automatically locating the wafer center and aligning the wafer below the exposure camera. In conjunction with a spherical air bearing support for the wafer, the air gauge also is used to achieve perfect parallel alignment between a portion of the wafer's surface and a reference plane of the camera.
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