Method and apparatus for setting a gap between first and second

Details Method and apparatus for setting a gap between first and second Method and apparatus for setting a gap between first and second

1987-06-11

1989-06-13

Willis, Davis L.

Optics: measuring and testing

By dispersed light spectroscopy

Utilizing a spectrometer

356363, G01B 902

Patent

active

048386936

ABSTRACT:
According to this invention, a method and apparatus for setting a gap to a predetermined distance between a mask and a wafer facing each other, are arranged as follows. First and second diffraction grating are formed on a mask and a wafer. The first diffraction grating is one-dimensional type and has parallel bars extending in a predetermined direction. The second diffraction grating is one-dimensional type and has parallel bars extending in a direction perpendicular to the predetermined direction. The second diffraction grating may be two-dimensional type having cross-bars. Laser beam is radiated from a light source onto the first diffraction grating. The light beams diffracted and transmitted through the first diffraction grating are transferred to the second diffraction grating. The light beams diffracted and reflected by the second diffraction grating are transferred to the first diffraction grating. The light beams are diffracted and transmitted through the first diffraction grating. Is detected, one of the diffracted light beams which are not oriented along a predetermined. The light beams reflected and diffracted by the surface of the first diffraction grating is transferred only by the prdetermined plane. Therefore, detected and diffracted light beam does not interfere with reflected light beams. The gap between the mask and the wafer can be adjusted and can be set to a predetermined distance.

REFERENCES:
patent: 4371264 (1983-02-01), Lacombat et al.
patent: 4596467 (1986-06-01), Bartelt
Y. Tarui, "VLSI Technology" Springer Verlag, Berlin 1986, pp. 135-137 and pp. 144-147. (English Translation of the Original Japanese Edition, 1981).

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