| 摘要 |
PURPOSE:To attain an excellent focusing without fail by constituting such that a nonoptical means corrects results obtained by optically detecting the interval between a projecting optical system and a substrate to be projected. CONSTITUTION:A reticule is lighted, and its pattern image is formed on a wafer W through a projecting lens 2. A slit optical image passing through a slit 42a is obliquely projected on the wafer, and its reflected light is image- formed on a slit plate 48 through a lens 45. A wafer placing stand 3 is moved in an optical axis direction AX by a focus signal FRS generated by a PSD 52, and further moved in the focus position of the projecting lens. By vibrating a vibration mirror 47, the focus position is corrected. An air distributor 7 feeds air, and a change in pressure due to a fine change in the distance between the lens 2 and the wafer W is detected, whereby a focus correcting unit 74 focuses and corrects the position. The disadvantages of an air micrometer system and an optical system are made up, and a pattern can be exposed on the optimum image forming surface of the optical system accordingly. |
