Method of high speed, high detection sensitivity inspection of repetitive and random specimen patterns
US5854674A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 29, 1997 |
| Grant date | Dec 29, 1998 |
| Priority date | — |
| Expiry date | May 29, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B27/46
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A patterned specimen inspection system achieves the inherent advantages of the die to statistical image (DSI) inspection mode for repetitive and random patterns and simultaneously achieves the inspection speed of the optical pattern filtering (OPF) mode. A preferred embodiment entails producing a patterned specimen wafer image with coherent optical spatial frequency filtering, as in the OPF mode, and carrying out defect detection by pixel comparison, as in the DSI mode. For repetitive and random pattern areas, implementation of the invention increases the inspection speed of the DSI mode to approach that of the OPF mode because image spatial filtering enables the use of a large sized unit pixel. For the repetitive pattern, the ability to use a large unit pixel size results from the complete removal of light energy from the repetitive patterns in the image. For the random pattern, spatial filtering can remove a large portion of the light energy from pattern features, but light energy from some pattern features remains. The optical dynamic range (ODR) for defect detection sets the minimum required electrical dynamic range (EDR) of the electronic imaging system for converting the tota…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.