System for automatic inspection of periodic patterns
US4771468A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 17, 1986 |
| Grant date | Sep 13, 1988 |
| Priority date | — |
| Expiry date | Apr 17, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T2207/30148
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for automatic inspection of periodic patterns typically found on patterned silicon wafers, printed circuit board, and the like is disclosed herein. The method comprises an inspection algorithm of two parts: a low-level algorithm and a higher level algorithm which includes, therein the operation of the low-level algorithm. The low-level algorithm utilizes the known periodicity of the pattern to find defects by comparing identical cells in the periodic array. The high-level algorithm comprises applying the low-level algorithm, some number of times (N) in succession on the image. An accumulator image is formed by adding the results of the low-level algorithm to create a separate image array where the pixels relate to the number of times that the pixel in the original image was detected as defective by the low-level algorithm. The apparatus for implementing the above method comprises a parallel/pipeline architecture for high speed processing and RAM LUT's to implement a plurality of subtract and compare functions.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.