Eddy current test method and apparatus for measuring conductance by determining intersection of lift-off and selected curves
US5552704A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 25, 1993 |
| Grant date | Sep 3, 1996 |
| Priority date | — |
| Expiry date | Jun 25, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L2924/0002
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for performing conductance measurements on a sample using an eddy current probe, without the need for measurement or knowledge of the separation between probe and sample. The probe comprises sense and drive coils mounted in close proximity to each other (or a single coil which functions as both a sense and drive coil), circuitry for producing AC voltage in the drive coil, and a meter for measuring in-phase and quadrature components of induced voltage in the sense coil. Look-up table data can be generated for use in subsequent measurements on samples of unknown conductance by performing eddy current measurements on samples having different known conductances to generate reference lift-off curves, processing the reference lift-off curves to determine a conductance function relating each known conductance to a location along a selected curve, and storing conductance values determined by the conductance function for different points on the selected curve as the look-up table data. An unknown sample conductance can then be determined by generating a lift-off curve from voltage measurements at different probe separations from the sample, determining a new intersect…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.