Stress measuring method and instrument
US7639348B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 5, 2004 |
| Grant date | Dec 29, 2009 |
| Priority date | — |
| Expiry date | Mar 10, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01L1/241
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The stress of a sample semiconductor wafer is detected with high accuracy in the form of an absolute value without rotating the sample or the entire optical system. A laser light R is subjected to photoelastic modulation in a PEM 6 to generate a birefringence phase difference and then it is passed through first and second quarter wavelength plates and passes through a semiconductor wafer D having residual stress. When it is passed through a test piece, the direction of the stress of the test piece is detected when the angle between the laser light R and a linear polarization light is 0 and 90 degrees. The transmitted electric signal is delivered to an analog/digital converter 16, and the signal is inputted to a signal processor thus generating transmission signal data. The signal processor reads out the stored reference signal data and the transmission signal data and calculates a reference birefringence phase difference and the absolute values of the birefringence phase difference.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.