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Apparatus for inspecting a circuit pattern drawn on a photomask used in manufacturing large scale integrated circuits

  • US 4,559,603 A
  • Filed: 09/23/1983
  • Issued: 12/17/1985
  • Est. Priority Date: 10/05/1982
  • Status: Expired due to Term
First Claim
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1. An apparatus for inspecting a circuit pattern of a photomask for manufacturing large scale integrated circuits comprising:

  • a measuring table on which the photomask is placed, said measuring table being movable along x and y directions;

    table driving means for continuously moving said measuring table in one direction;

    table position measuring means for measuring a position of said measuring table;

    optical pattern measuring means for scanning the photomask in a direction substantially perpendicular to the moving direction of said measuring table to sequentially produce analog measured signals at measured points along the scanning direction of the photomask in response to light transmitted through the photomask;

    analog-to-digital converting means coupled to said optical pattern measuring means for converting the analog signal to multi-level digital measured data;

    measured point calculation circuit means for calculating, in response to said table position measuring means, the position of a measured point within a pixel of the photomask being measured by said optical pattern measuring means to provide position data of the measured point;

    reference data calculation circuit means for calculating reference data, as multi-level digital data, which is to be obtained as measured data when a design circuit pattern is measured by said optical pattern measuring means at each of the measured points on the basis of the design pattern data represented by binary data for each of a plurality of pixels within a two-dimensional pixel array centered at the pixel including the measured point on the photomask being measured by said optical pattern measuring means, the position data of the measured point on the photomask calculated by said measured point calculation circuit means, and sensitivity distribution characteristic data of an image sensor element of said optical pattern measuring means; and

    defect detecting means for comparing the measured data from said analog-to-digital converting means with the reference data calculated by said reference data calculation circuit means to detect the presence or absence of a pattern defect at the measured point.

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