APPARATUS FOR INSPECTION OF PHASE SHIFT MASK

摘要

PURPOSE:To provide the means for inspecting a phase shift mask capable of easily measuring the phase difference of the high-density parts of mask patterns without errors by using light of short wavelengths, such as (9) rays and (i) rays. CONSTITUTION:This apparatus is constituted by inserting an optical path length changing device having a wedge type prism periodically moving back and forth into the sample optical path of a Mach-Zehunder interferometer and a reference light projector having a dummy plate into the reference optical path of this interferometer, respectively, and is so constituted as to obtain interference fringes and output data by controlling the image output of a CCD camera which receives the exit light of the interferometer by the pulse output of the optical path changing device.