Method and apparatus for checking pattern

• US 5,048,094 A
• Filed: 10/24/1989
• Issued: 09/10/1991
• Est. Priority Date: 11/29/1988
• Status: Expired due to Fees

• Current Assignee: Nippon Seiko Kabushiki Kaisha (NSK Limited)
• Original Assignee: Nippon Seiko Kabushiki Kaisha (NSK Limited)
• Inventors: Nakano, Takahiro, Aoyama, Yoshiyuki, Kanasashi, Osamu
• Primary Examiner(s): BRINICH, STEPHEN M
• Application Number:
  US07/426,574
• Time in Patent Office: 686 Days
• Field of Search: 382/8, 382/46, 382/106, 358/237
• US Class Current: 382/151
• CPC Class Codes: G01R 31/308 using non-ionising electromagnetic radiation, e.g. optical radiation investigating or analysing materials by the use of optical means G01N21/00; image analysis G06T7/00
• CPC Class Codes: G03F 7/70633 Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
• CPC Class Codes: G06T 2207/30141 Printed circuit board [PCB]
• CPC Class Codes: G06T 7/0004 Industrial image inspection

Abstract

A pattern formed on an object under check such as a mask, printed substrate, etc., is scanned by a CCD camera, and check pattern data for one scanning line obtained from the CCD camera is divided into a plurality of pixel groups and stored in shift register groups. The check pattern data is compared with a master pattern data representing the external shape of a master pattern to calculate an inclination of the check pattern (pattern to be checked) with respect to the master pattern. The order of reading addresses of the shift register groups is changed in accordance with the inclination so that the check pattern data matches the master pattern data. Thereafter, the check pattern data is compared with the master pattern data to detect a defect in the check pattern to thereby avoid erroneous judgment due to an angular deviation between the check pattern and the master pattern.

Claims

1. In a method for checking a pattern wherein an object under check having a pattern to be checked formed thereon is scanned two-dimensionally relative to an imaging device to obtain check pattern data, and the check pattern data is compared with previously stored master pattern data to check for a defect in the pattern to be checked, the improvement comprising the steps of:

dividing check pattern data for each one scanning line from the imaging device into a plurality of pixel groups and storing the check pattern data in a memory means;

calculating an inclination of the pattern to be checked by comparing the store check pattern data with the master pattern data;

matching the check pattern data and the master pattern data with each other by changing the order of reading of one of the check pattern data and the master pattern data in accordance with the inclination of the pattern data to be checked; and

comparing the check pattern data with the master pattern data.

2. The improvement in a method for checking a pattern according to claim 1 wherein the comparison between the comparison pattern data or the master pattern data and the check pattern data is performed by taking the exclusive OR of the check pattern data and the master pattern data.

3. In an apparatus for checking a pattern wherein an object under check having a pattern to be checked formed thereon is scanned two-dimensionally relative to an imaging device to obtain check pattern data, and the check pattern data is compared with previously stored master pattern data to check for a defect in the pattern to be checked, the improvement comprising:

means for dividing the check pattern data for each one scanning line from the imaging device into a plurality of pixel groups and for storing the check pattern data in a memory means;

means for detecting an inclination of the pattern to be checked by comparing the stored check pattern data with the master pattern data;

means for matching the check pattern data and the master pattern data with each other by changing the order of reading of one of the check pattern data and the master pattern data in accordance with a detected result of the inclination detection means; and

means for comparing the check pattern data with the master pattern data.

4. The improvement in an apparatus for checking a pattern according to claim 3 wherein the means for extracting a defective portion extracts the defective portion by taking the exclusive OR of one of the comparison master pattern data and the master pattern data, and the check pattern data.

5. In a method for checking a pattern wherein an object under check having a pattern to be checked is scanned two-dimensionally relative to an imaging device to obtain check pattern data, and the check pattern data is compared with previously stored master pattern data to check for a defect in the pattern to be checked, the improvement comprising the steps of:

forming a deviation quantity corresponding to a pattern portion whose accuracy in a defect recognition in the master pattern data is low;

forming comparison master pattern data based on the deviation allowing pattern data and the master pattern data;

forming contour data of the comparison master pattern data;

extracting a defective portion by comparing the comparison pattern data with the check pattern data; and

judging the absence or presence of a defect in the pattern to be checked by masking the extracted defective portion with the contour data.

6. The improvement in a method for checking a pattern according to claim 5 wherein the comparison between the comparison pattern data or the master pattern data and the check pattern data is performed by taking the exclusive OR of the check pattern data and the master pattern data.

7. In the apparatus for checking a pattern wherein an object under check having a pattern to be checked formed thereon is scanned two-dimensionally relative to an imaging device to obtain check pattern data, and the check pattern data is compared with previously stored master pattern data to check for a defect in the pattern to be checked, the improvement comprising:

means for forming a deviation allowing pattern which is set to a predetermined deviation quantity corresponding to a pattern portion whose accuracy in a defect recognition in the master pattern data is low;

means for forming contour pattern data of the comparison master pattern data;

means for extracting a defective portion by comparing the comparison master pattern data with the check pattern data; and

means for masking the extracted defective portion with the contour pattern data.

8. The improvement in an apparatus for checking a patter according to claim 7 wherein the means for extracting a defective portion by taking the exclusive OR of one of the comparison master pattern data and the master pattern data, and the check pattern data.

9. In a method for checking a pattern wherein an object under check having a pattern to be checked is scanned two-dimensionally relative to an imaging device to obtain a check pattern data, and the check pattern data is compared with a previously stored master pattern data to check for a defect of the pattern to be checked, the improvement comprising the steps of:

dividing the check pattern data for each one scanning line from the imaging device into a plurality of pixel groups and storing the check pattern data in a memory means;

calculating an inclination of the pattern data to be checked by comparing the stored check pattern data with the master pattern data;

matching the check pattern data and the master pattern data in accordance with the inclination of the pattern to be checked;

forming a deviation allowing pattern which is set to a predetermined deviation quantity corresponding to a pattern portion whose accuracy in a defect recognition in the master pattern data is low;

forming comparison master pattern data based on the deviation allowing pattern data and the master pattern data;

forming contour pattern data of the comparison master pattern data;

extracting a defective portion by comparing the comparison master pattern data with the check pattern data; and

judging the absence or presence of the check pattern defective portion by masking the extracted defective portion with the contour pattern data.

10. The improvement in a method for checking a pattern according to claim 9 wherein the comparison between the comparison pattern data or the master pattern data and the check pattern data is performed by taking the exclusive OR of the check pattern data and the master pattern data.

11. In ana apparatus for checking pattern wherein an object under check having a pattern to be checked is scanned two-dimensionally relative to an imaging device to obtain a check pattern data, and the check pattern data is compared with a previously stored master pattern data to check for a defect of the pattern to be checked, the improvement comprising:

means for dividing check pattern data for each one scanning line from the imaging device into a plurality of pixel groups and for detecting an inclination of the check pattern by comparing the stored check pattern data with the master pattern data;

means for matching the check pattern data and the master pattern data in accordance with a check result of the inclination detection means;

means for forming a deviation allowing pattern which is set to a predetermined deviation quantity corresponding to a pattern portion whose accuracy in a defect recognition in the master pattern data is low;

means for forming comparison master pattern data based on the deviation allowing pattern data and the master pattern data;

means for forming contour pattern data of the comparison master pattern data;

means for extracting a defective portion by comparing the comparison master pattern data with the check pattern data; and

means for masking defective portion extracting data with the contour pattern data.

12. The improvement in an apparatus for checking a patter according to claim 11 wherein the means for extracting a defective portion by taking the exclusive OR of one of the comparison master pattern data and the master pattern data, and the check pattern data.