Method for nondestructive measurement of dislocation density in GaAs
US5512999A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 6, 1995 |
| Grant date | Apr 30, 1996 |
| Priority date | — |
| Expiry date | Mar 6, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/9506
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method for nondestructively measuring dislocation density in a GaAs wafer is disclosed in which an unetched GaAs wafer is tested for fractional transmission (T) of light at a plurality of points over its surface. A light beam from a suitable source such as a tungsten-halogen lamp is passed through a monochromator and focused by a lens on the wafer. The fractional transmission (T) of light through the wafer is detected and the absorption coefficient (.alpha.) is calculated at each of the points from the detected values of the fractional transmission. Regions of dislocation density in the wafer are determined nondestructively from the absorption data by dividing the values of .alpha. into equal segments bounded by the minimum and the maximum calculated values. A histogram is plotted of the number of values of .alpha. in each segment versus the value of .alpha. at the midpoint of the segment. A reference .alpha. point is selected from the histogram coinciding with the point approximately at which the first minimum value of .alpha. occurs following the first maximum value of .alpha.. A map of the coordinate positions of all the values of .alpha. that are less than or equal to the ref…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.