| 摘要 |
A system for inspecting a phase-shifted photolithographic mask. This inspection system includes an illumination optical system for illuminating a mask, an imaging optical system for focusing an image of a pattern to be inspected on the mask, and detecting means for detecting the image of the inspection pattern whereby in accordance with one form, the amount of phase shift ( pi + delta ) is determined in accordance with the light quantity ratio between the images of phase-shifter deposited portions and phase-shifter non-deposited portions of the inspection pattern in a defocus condition. In accordance with another form, the direction of incidnece of an illuminating light on the mask is changed in such a manner that of the light transmitted through the inspection pattern the other beams than the 0-order diffracted beam and either one of the +/-first-order diffracted beams are intercepted at a Fourier transform plane within the imageing optical system or alternatively the 0-order diffracted beam and either one of the +/-first-order diffracted beams are passed through the Fourier transform plane within the imaging optical system at positions which are symmetric with the optical axis of the imaging optical system, and the amount of phase shift ( pi + delta ) of the phase shifters is determined in accordance with the amount of shift ( DELTA x) within the imaging plane of the pattern image (interference pattern) detected.
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