Device and method for detecting an end point in polishing operation
US5213655A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 2, 1992 |
| Grant date | May 25, 1993 |
| Priority date | — |
| Expiry date | Mar 2, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B7/105
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The present invention relates to a method and apparatus for remotely detecting impedance. It is specifically adapted for use on a polishing machine wherein the end point of polishing for removing a surface layer during the processing of semiconductor substrates is detected. A first, or stationary coil having a high permeability core is wound having an air gap and an AC voltage is applied to the stationary coil to provide a magnetic flux in the air gap. A second coil is mounted for rotation on the polishing table, in a position to periodically pass through the air gap of the stationary coil as the table rotates. The second coil is connected at its opposite ends to contacts which are embedded in the surface of the polishing wheel. The contacts are positioned to engage the surface of the substrate which is being polished and provide a load on the second or rotating coil. The rotating coil, when it is in the air gap of the stationary coil, will perturb the flux field therein as a function of the resistance of the load caused by the contacts contacting either a conducting surface or a non-conducting surface. This perturbance of the flux field is measured as a change in the induced volta…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.