Apparatus for detecting the defects of the mask pattern using sp

Details Apparatus for detecting the defects of the mask pattern using sp Apparatus for detecting the defects of the mask pattern using sp

1975-06-27

1976-08-03

McGraw, Vincent P.

Optics: measuring and testing

Document pattern analysis or verification

350 81, 350162SF, 356237, 356239, G06K 908, G01N 2116, G01N 2132

Patent

active

039726169

ABSTRACT:
Two kinds of light sources, one of which emits a coherent light and the other of which emits incoherent light, are provided. The coherent light and incoherent light respectively emitted from the two different kinds of light sources, proceed on the same optical axis. A photomask, such as for an integrated-circuit, or other objects, which have linear straight line features and nonlinear defects, are simultaneously illuminated by the coherent light and incoherent light.
The two kinds of light which pass through the photomask or other objects are transformed into a Fourier-transform pattern by a transform lens. A spatial filter, having a plurality of arms which extend in predetermined directions from the center thereof, is provided on the focal plane of the transform lens.
The spatial filter suppresses the passing of coherent light having information of the linear straight line features. The coherent light which has information of the defects of the photomask is not suppressed by the spatial filter. The coherent light and incoherent light passing through the spatial filter are directed to an image plane.
As a result thereof, an image of the photomask or other object, obtained by the incoherent light and an image of the defects of the photomask or other objects obtained by the coherent light, are simultaneously projected on each other on the image plane.

REFERENCES:
patent: 3614232 (1971-10-01), Mathisen
patent: 3658420 (1972-04-01), Axelrod
patent: 3738752 (1973-06-01), Heinz et al.

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