Apparatus for inspecting defects in a periodic pattern

Details Apparatus for inspecting defects in a periodic pattern Apparatus for inspecting defects in a periodic pattern

1980-10-30

1982-11-23

Corbin, John K.

Optics: measuring and testing

Inspection of flaws or impurities

Transparent or translucent material

350162SF, G01N 2100

Patent

active

043602690

ABSTRACT:
The apparatus of this invention is used for inspecting defects in a periodic pattern. The apparatus comprises a device for forming a Fourier transformed pattern of the periodic pattern and a filter for passing predetermined spatial frequency ranges of the Fourier transformed pattern. The predetermined spatial frequency ranges are lower than a spatial frequency which coincides with a first order diffraction of the Fourier transformed pattern.

REFERENCES:
patent: 3614232 (1971-10-01), Mathisen
patent: 3790280 (1974-02-01), Heimz et al.
Iwamoto et al., "Rotation-, Shift-, and Magnification-Insensitive Periodic Pattern-Defects Optical Detection System", Applied Optics, vol. 19, No. 7, pp. 1146-1200, Apr. 1980.
Konowa Ichuk et al., "A Rapid Method for Assessing the Quality of Sieves", Powder Technology, vol. 13, No. 1, pp. 97-101, Feb. 1976.
Will et al., "Filtering of Defects in Integrated Circuits with Orientation Independence", Applied Optics, vol. 10, No. 9, pp. 2097-2100, Sep. 1971.
Watkins, "Inspection of Integrated Circuit Photomasks with Intensity Spatial Filters", Proc. IEEE, pp. 1634-1639, Sep. 1969.
Proceedings of the IEEE, Apr. 1972, pp. 447-448, "Intensity Spatial Filtering Applied to Defect Detection in Integrated Circuit Photo Masks" by Norman N. Axelrod.

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