PURPOSE: To provide a measuring optical system allowing uniform focusing for each pattern by decreasing he numerical aperture of the objective lens of a microscope effectively in the light receiving system of a positional shift measuring equipment.
CONSTITUTION: Pinhole plates 7x, 7y for effectively decreasing the numerical aperture of the objective lens 61 of a microscope are inserted detachably between intermediate lenses 642, 652 and cylindrical lenses 643, 653 of a conventional measuring optical system in order to increase the depth of focus thus allowing uniform focusing for various patterns having different heights formed on the surface of a wafer 1. Consequently, positional shift is measured accurately while shortening the measuring time and sustaining the intensity of irradiating light for each pattern without sacrifice of magnification and view of the objective lens 61.
NAKADA MASAHIKO
MATSUMOTO SHINICHI
