Sensing the presence of a wafer
US6796881B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 9, 2001 |
| Grant date | Sep 28, 2004 |
| Priority date | — |
| Expiry date | Oct 3, 2021 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S414/136
- WIPO fieldMachine tools
- WIPO sectorMechanical engineering
Abstract
In a machine for planarizing wafers, when a spindle carrier descends over the load station, it needs a way of determining whether it should descend to a first position suitable for depositing a wafer onto the load station or whether it should descend to a lower second position suitable for acquiring a wafer that is already present on the load station. The present invention provides a way of making this determination. The load station includes three upwardly-directed nozzles for use in supporting a wafer on three separate spaced cushions of purified water. The nozzles are supplied through branch conduits from a supply main. When no wafer is present, the pressurized water meets with little resistance as it is discharged from the nozzles. Accordingly, the pressure in the branches is relatively low. In contrast, when a wafer is present the wafer partially impedes the discharge of the water from the nozzles, causing the pressure in the branches to be greater than when no wafer is present. In accordance with the present invention, the pressure in one of the branches is sensed. A low pressure indicates the absence of a wafer and signifies that the spindle carrier should descend to the fir…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.