| 摘要 |
PURPOSE:To secure position aligning accuracy by satisfying the relationship, wherein the value obtained by dividing the square of the central wavelength of an optical beam by the half-value width of the wavelength is approximately equal with respect to the double value of the gap length between a fist body and a second body. CONSTITUTION:A beat signal IM (0, 1) is obtained at a first position in the position aligning direction of the interference light occurring on the side of the first grids 25a and 26a forming a pair. A beat signal IW (0, 1) is obtained at the first position in the position aligning direction of the interference light occurring on the side of the second grids 25b and 26b forming a pair. The central wavelength of the optical beam emitted from a light source is made to be lambda0. The half-value width of the wavelength is made to be DELTAlambda. The gap length of diffraction gratings 23 and 24, i.e., the gap length between a mask and a wafer, is made to be Z. Then, the device, which satifies the relationship of lambda0<2>/DELTAlambda<=2Z is used. Thus, the interference of the light wave UM2 and the light wave UM3 with the light wave UM1 can be prevented. Only the position information of the mask can be included in the beat signal IM (0, 1). |
