Foreign particle inspection apparatus and method with front and back illumination
US5539514A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 30, 1994 |
| Grant date | Jul 23, 1996 |
| Priority date | — |
| Expiry date | Jun 30, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/94
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method of inspecting a phase shift reticle comprising a transparent or translucent substrate, a circuit pattern of an opaque film formed on the front surface of the substrate and a pattern of a transparent or translucent film formed on the front surface of the substrate comprises: obliquely projecting a front illuminating light beam on the front surface of the substrate by a front illuminating system; concentrating scattered light scattered by the surface of the substrate and the surfaces of the patterns, obliquely projecting a back illuminating light beam on the back surface of the substrate by a back illuminating system, concentrating transmitted-and-diffracted light transmitted and diffracted by the substrate and the patterns; intercepting the scattered light scattered by the patterns and the transmitted-and-diffracted light transmitted and diffracted by the patterns with spatial filters disposed on Fourier transform planes, focusing the scattered light and the transmitted-and-diffracted light transmitted by the spatial filters on detectors; and comparing detection signals provided by the detectors to see if there are any foreign particles on the phase shift reticle.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.