US 6,444,382 B1Granted

Straight line defect detection tool

AssigneeApplied Materials, Inc.

InventorsNimrod Sarig, Gadi Greenberg

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Abstract

A method and apparatus for inspecting the straightness of edges of features on a reticle is provided wherein the feature edges are analyzed for local defects as small groups of pixels, rather than pixel-by-pixel. In one embodiment, the reticle is imaged to produce pixels having a gray level and associated with an x and a y coordinate. A small array of pixels, such as a 2×2 array, that lays on an edge of the target feature is identified, a plane is calculated based on the x coordinate, the y coordinate and the gray level of each of the pixels in the array, and an angle α between a reference line and a line at the intersection of the calculated plane and a reference plane is calculated. Several other edge-straddling arrays adjacent to the first array are identified, their respective angles α are calculated, and all the α's are compared. If the α's are substantially equal, it is determined that the target feature edge is straight, and if the α's are not substantially equal, it is determined that the target feature edge is curved. A corresponding reference feature image is analyzed in the same way as the target feature image, and a defect is determined to exist in the target feature when the target feature edge is curved and the reference feature edge is straight.

Claims10

Dependent claims

An inspection tool for inspecting a target feature formed on a surface, the inspection tool comprising:

an imager to image the target feature to produce a matrix of pixels representative of the target feature, each pixel having a gray level and associated with an x and a y coordinate corresponding to its respective location on the surface;
and
a processor for:
identifying a current pixel and a first plurality of pixels adjacent to the current pixel and each other associated with the feature edge;
determining a first plane based on the x coordinate, the y coordinate and the gray level of each of the current pixel and the first plurality of pixels;
calculating a first angle between a first reference line and a first intersection line at the intersection of the first plane and a reference plane;
identifying a second current pixel and a second plurality of pixels adjacent to the second current pixel and each other associated with the feature edge;
determining a second plane based on the x coordinate, the y coordinate and the gray level of each of the second current pixel and the second plurality of pixels;
calculating a second angle between a second reference line corresponding to the first reference line, and a second intersection line at the intersection of the second plane and the reference plane;
and
comparing the first and second angles to determine whether a defect exists in the target feature.

8 more elements

Dependencies are inferred from the claim text.