METHOD AND APPARATUS FOR ALIGNING POSITION USING DIFFRACTION GRATING

摘要

PURPOSE: To provide a method and an apparatus, wherein the signals for detecting positions are not governed by process conditions and the like. ;CONSTITUTION: Light sources 1a and 1b emit lights having two frequencies, whose wavelengths are different from each other. The heterodyne-interference diffracted-lights obtained from diffraction gratings 32 and 34 by the incidence of the two-frequency lights are guided into photo detectors. Thus, the first beat signal caused by the diffracted light having the wavelength from the diffraction grating 32 is obtained with detectors 12a and 12b, and the second beat signal caused by the diffracted light having the wavelength from the diffraction grating 34 is obtained with detectors 16a and 16b. A signal processing part 17a selects the stabilized first and second beat signals based on the same wavelength, outputs the control signal into a moving mechanism based on the signals and aligns the positions of a mask 30 and a wafer 31.;COPYRIGHT: (C)1996,JPO