System for locating and measuring an index mark on an edge of a wafer
US6342705B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 10, 1999 |
| Grant date | Jan 29, 2002 |
| Priority date | — |
| Expiry date | Sep 10, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L21/681
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
In a system for locating and measuring an index mark on an edge of a wafer, a wafer to be examined is positioned and centered on a chuck in a horizontal chuck position such that an index mark is oriented within first and second index mark orientation features disposed on the chuck. The chuck is translatable, tiltable between horizontal and vertical positions, and rotatable over an angle subtended by the index mark orientation features of the chuck. A laser beam from a laser beam optical profiler is focussed on the surface of the wafer at a distance proximate the wafer edge and proximate the first index mark orientation feature of the chuck. The chuck is rotated in a direction from the first to the second index mark orientation feature whereby a reflected portion of the laser beam generates data corresponding to the angular location of index mark edges. An index mark center location is computed. The chuck is tilted to a vertical chuck position, and the index mark is measured by the focussed laser beam to provide index mark data which serve as a basis for accepting or rejecting a wafer.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.