Quality monitor and monitoring technique employing optically stimulated electron emmission
US5393980A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 11, 1993 |
| Grant date | Feb 28, 1995 |
| Priority date | — |
| Expiry date | May 11, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/33
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A light source directs ultraviolet light onto a test surface and a detector detects a current of photoelectrons generated by the light. The detector includes a collector which is positively biased with respect to the test surface. Quality is indicated based on the photoelectron current. The collector is then negatively biased to replace charges removed by the measurement of a nonconducting substrate to permit subsequent measurements. Also, the intensity of the ultraviolet light at a particular wavelength is monitored and the voltage of the light source varied to maintain the light a constant desired intensity. The light source is also cooled via a gas circulation system. If the test surface is an insulator, the surface is bombarded with ultraviolet light in the presence of an electron field to remove the majority of negative charges from the surface. The test surface is then exposed to an ion field until it possesses no net charge. The technique described above is then performed to assess quality.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.