Apparatus for inspecting a circuit pattern drawn on a photomask used in manufacturing large scale integrated circuits
First Claim
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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Accused Products
Abstract
A photomask on which a circuit pattern is drawn is placed on an x-y table and is illuminated by a light source. A linear image sensor, on which the circuit pattern is imaged, measures the circuit pattern along the direction substantially perpendicular to a moving direction of the x-y table to generate an analog signal in units of measured positions on the mask. In order to eliminate the need for matching the size of the pixel to be measured with the pixel size of the design pattern data and allow effective detection of a defect smaller than the pixel size, an analog-to-digital converter is arranged to convert the analog signal to multi-level digital data, and a measured point calculation circuit calculates the position of the measured point in units smaller than the pixel size unit in accordance with the position of the x-y table. A reference data calculation circuit is provided to calculate multi-level reference digital data which is to be obtained when the design pattern is measured at a calculated measured point taking sensitivity distribution characteristics (including resolution characteristics of lens) of image sensor elements into consideration. A defect detector compares the measured data with the reference data to detect the presence or absence of defects of the circuit pattern on the photomask.
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Citations
11 Claims
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1. An apparatus for inspecting a circuit pattern of a photomask for manufacturing large scale integrated circuits comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification
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- Resources
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Current AssigneeTokyo Shibaura Denki Kabushiki Kaisha (Toshiba Corporation)
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Original AssigneeTokyo Shibaura Denki Kabushiki Kaisha (Toshiba Corporation)
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InventorsYoshikawa, Ryoichi
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Primary Examiner(s)Wise, Edward J.
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Application NumberUS06/535,334Time in Patent Office816 DaysField of Search364/490, 364/491, 364/559, 364/488, 364/489, 364/520, 356/394, 356/398, 356/448, 356/237, 358/101, 358/106, 250/491.1, 250/492.2US Class Current356/237.5CPC Class CodesG03F 1/84 InspectingH01L 21/30 Treatment of semiconductor ...
