Edge finding in wafers
US4752898A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 28, 1987 |
| Grant date | Jun 21, 1988 |
| Priority date | — |
| Expiry date | Jan 28, 2007 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S414/139
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
A system for finding the orientation of a substantially circular disk shaped wafer with at least one flat region on an edge thereof, in which the wafer is spun one 360 degree turn on a chuck and the edge position is measured by a linear array to obtain a set of data points at various wafer orientations. The rotation axis may differ from the wafer center by an unknown eccentricity. The flat angle is found by fitting a cosine curve to the data, subtracting the expected data derived from the cosine curve from the actual data to obtain a deviation. The angle of maximum deviation of the data from the cosine curve is a first estimate of the flat angle. The estimate may be corrected for errors due to a finite number of data points and wafer eccentricity by calculating an adjustment angle from data points on the wafer flat. After determining the flat angle, the wafer is spun to the desired orientation. The wafer eccentricity may be calculated from four of the data points located away from the flat edge region, and the wafer is then centered.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.