Method of detecting and reviewing pattern defects

• US 4,985,927 A
• Filed: 03/25/1988
• Issued: 01/15/1991
• Est. Priority Date: 03/25/1988
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Norwood, David A., Manns, Willims G., Wood, Anthony B.
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Cammarata, Michael R.
• Application Number:
  US07/173,706
• Time in Patent Office: 1,026 Days
• Field of Search: 382/8, 382/34, 382/20, 382/21, 382/23, 358/106, 356/237
• US Class Current: 382/149
• CPC Class Codes: G03F 7/7065 Defects, e.g. optical inspection of patterned layer for defects
• CPC Class Codes: G06T 2207/20021 Dividing image into blocks, subimages or windows
• CPC Class Codes: G06T 2207/30141 Printed circuit board [PCB]
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

A laser pattern inspection and/or writing system which writes or inspects a pattern on a target on a stage, by raster scanning the target pixels. Inspection can also be done by substage illumination with non-laser light. A database, organized into frames and strips, represents an ideal pattern as one or more polygons. Each polygon'"'"'s data description is contained within a single data frame. The database is transformed into a turnpoint polygon representation, then a left and right vector representation, then an addressed pixel representation, then a bit-mapped representastion of the entire target. Most of the transformations are carried out in parallel pipelines. Guardbands around polygon sides are used for error filtering during inspection. Guardbands are polygons, and frames containing only guardband information are sent down dedicated pipelines. Error filtering also is done at the time of pixel comparisons of ideal with real patterns, and subsequently during defect area consolidation. Defect areas are viewed as color overlays of ideal and actual target areas, from data generated during real time. Defect areas can be de-zoomed to allow larger target areas to be viewed. An autofocus keeps the scanning laser beam in focus on the target. The inspection system is used to find fiducial marks to orient the target prior to raster scanning. IC bars are provided with alignment marks for locating each IC bar. Interferometers or glass scale encoders allow the stage position to be known.

Claims

1. A computerized method of pattern defect review, comprising the steps of:

providing a database representation of an ideal pattern, the ideal pattern being comprised of one or more polygons defining the ideal pattern, and each polygon defining an ideal pattern is contained in a frame of data;

scanning a target with a laser, the reflected light from the target producing optical data representative of the pattern on the target;

inputting the optically generated data representing the pattern on a target;

generating a bit-mapped data representation of the ideal pattern, from the database representation with only those frames of data corresponding to the scanned area on the target;

comparing the bit-mapped data representation of the ideal pattern with the optically generated data representing the pattern on the target to identify and generate data representative of selected defect areas;

storing data identifying the locations of selected, defect areas wherein miscompares between the reference data and optically generated data occurred;

generating a bit-mapped data representation of a selected defect area, the bits in the bit-mapped area corresponding to pixels of the selected defect area; and

selecting every Nth bit, where N is from the set (2, 4, 6 or

     8), to de-zoom that portion of the database representation which corresponds to the selected defect area.

2. The method of claim 1, further comprising the steps of:

displaying on a video display, the generated bit-mapped data representation of the selected defect area.

3. The method of claim 2, wherein the step of generating the bit-mapped data representation of the selected defect area, takes place at the time of the step of displaying the data.

4. The method of claim 1, wherein the optically generated data comprises:

pixel data representing the individual pixels on the target, including the pattern thereon.

5. The method according to claim 1, wherein the comparing the data representative of the ideal pattern with the optically generated data to identify and generate data representative of selected defect areas generates data related to the defect area, the number of pixels and X-Y extremes of the of the defect area and the type of defect;

and wherein the step of storing data, includes storing, for selected defect areas, only the area in number of pixels, the X-Y extremes, and the type of defect.