Nikon Corporation

Keiji Inada

Mikihiko Ishii

Tetsuya Koike

Yutaka Ichihara

Masato Shibuya

Takashi Gemma

Shuji Toyonaga

A position detecting apparatus includes a light source, which supplies a detecting light; a light-collecting optical system which collects the detecting light onto a diffracted light generating portion provided on the object; a light guiding optical system which guides, to a predetermined position, a diffracted measuring light generated from the diffracted light generating portion by receiving the detecting light and a reference light generated from a reference surface by receiving the detecting light; and a photodetector which is arranged at the predetermined position and which detects interference fringes generated by the diffracted measuring light and the reference light. Three-dimensional positional information of, for example, a mask pattern surface or an exposure surface of a photosensitive substrate can be highly accurately detected by a relatively simple construction.

Interferometric apparatus for detecting 3D position of a diffracting object

A position detecting apparatus includes a light source which supplies a detecting light; a light-collecting optical system which collects the detecting light onto a diffracted light generating portion provided on the object; a light guiding optical system which guides, to a predetermined position, a diffracted measuring light generated from the diffracted light generating portion by receiving the detecting light and a reference light generated from a reference surface by receiving the detecting light; and a photodetector which is arranged at the predetermined position and which detects interference fringes generated by the diffracted measuring light and the reference light. Three-dimensional positional information of, for example, a mask pattern surface or an exposure surface of a photosensitive substrate can be highly accurately detected by a relatively simple construction.

In an interferometer, reflected light from a reference surface and a subject surface are introduced to an imaging optical system through a beam splitter, and an interference fringe formed from light reflected from the both surfaces is observed with a detection optical system. An alignment optical member is disposed in an optical path between the imaging optical system and an image plane of the interference fringe such that the rear focal point of the alignment optical member is located at the image plane. The alignment optical member is inserted in the optical path in aligning the subject surface and is removed in measuring the interference fringe. Accurate alignment of the subject surface is easily attained. A beam expander is interposed between a polarizing beam splitter and the subject surface and a 90.degree. retarder is interposed between the beam expander and the subject surface. The 90.degree. retarder is constructed of one or a plurality of reflecting mirrors formed of dielectric multilayer films. Noise introduced to the imaging optical system is minimized.

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Keiji Inada