| 摘要 |
An exposure method for a photolithographic process uses a projection exposure apparatus including a projection optical system. The surface of a first shot area on a wafer is caused to be coincident with an image plane of the projection optical system within an exposure field thereof so as to achieve focused condition, and an image of a reticle pattern is transferred onto the first shot area. Then, a second shot area is moved into the exposure field, during which the vertical position of the wafer is corrected by means of a Z/levelling-stage so as to compensate for the variation in the vertical position of the wafer W which could otherwise occur depending on the angle formed between the running plane of the wafer stage and the image plane. Then, an AF sensor system is used to measure and store the defocus amount of the second shot area relative to the image plane. Then, focusing and exposure are performed for the second shot area. This procedure is repeated for the shot areas on the wafer so as to obtain a plurality of defocus amounts, from which any foreign matter existing on the bottom of the wafer is detected. In another embodiment, after the first shot area is exposed and the wafer is positioned for the second shot area, a tilt angle of the wafer is measured and stored, and then the vertical position and tilt angle of the wafer are caused to be coincident with those of the image plane, and the second shot area is exposed. Any foreign matter is detected from a distribution of the tilt angles on the surface of the wafer.
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