Optical wafer positioning system
US5530550A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 21, 1994 |
| Grant date | Jun 25, 1996 |
| Priority date | — |
| Expiry date | Dec 21, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/956
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The position detector has a sensitivity characteristic graded along a direction transverse to the surface, so that the output of the position detector is used to determine a height of the surface. A surface height detection and positioning device for use in a surface inspection system. An incident beam of light impinges obliquely upon the surface, and a position detector is disposed to receive specularly reflected light, producing a plurality of electrical signals, with a mechanical window, defining an aperture, placed in front of the detector. The aperture's width, along the scan direction, is of sufficient size so as to create a train of signals from each of the plurality of electrical signals, having a frequency equal to the scan frequency. These electrical signals carry information responsive to both the position of reflected beam impinging on the detector and the beam's intensity and are, in turn, related to a height of the surface. To abrogate information responsive to intensity variations at the position sensitive detector, an electronic circuit is employed which determines the sum and the difference of the plurality of signals relating to wafer height and beam intensity, pr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.