Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Patent
1989-12-20
1991-04-16
Fields, Carolyn E.
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
2503581, 356 30, 356 31, G01N 2188, G01N 2135
Patent
active
050085425
ABSTRACT:
A method and system for measuring whole-wafer etch pit density (.rho..sub.D) is disclosed in which an etch GaAs wafer is tested for fractional transmission at a plurality of points over its surface. The fractional transmission (T) of light through the wafer is detected, amplified and fed to a computer where at least two points of transmission measurement are selected for calibration. From these measurements, together with an estimate of the average etch pit size (area), the values for fractional transmission in regions of low etch pit density T.sub.O and high etch pit density T.sub.E may be calculated, and used to convert transmission data directly to etch pit density (.rho..sub.D) according to the equation ##EQU1##
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Dudley Scott C.
Look David C.
Mier Millard G.
Sewell James S.
Sizelove John R.
Beyer James E.
Fields Carolyn E.
Kundert Thomas L.
Singer Donald J.
The United States of America as represented by the Secretary of
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