Optics: measuring and testing – Of light reflection – By comparison
Patent
1989-09-25
1991-04-16
Rosenberger, Richard A.
Optics: measuring and testing
Of light reflection
By comparison
356369, 356346, G01N 2155
Patent
active
050077414
ABSTRACT:
The purpose of the invention is to detect impurities in a semiconductor wafer (20). A laser (21) forms a light beam having a high proportion of its power at an optical frequency capable of being absorbed by the impurity to be measured. The beam is split into first (25) and second (26) light components, one of which is directed at the surface of the semiconductor wafer (20) to be tested and the other at a reference semiconductor wafer (27) containing a known quantity of the impurity to be measured. The light intensities reflected from the two wafers is detected by photodetectors (29, 30) and their difference is taken as a factor in measuring the impurity density in the wafer under test. A polarizer (33) polarizes the beam such as to maximize p-type component and minimize s-type components. Reflection from each of the two wafers (20, 27) is at the principal angle.
REFERENCES:
patent: 3600099 (1971-08-01), Schoeffel
patent: 3623818 (1971-11-01), Gardner
patent: 4444499 (1984-04-01), Akiyama et al.
patent: 4590574 (1986-05-01), Edmonds et al.
"Analysis of Infrared Spectra for Oxygen Measurements in Silicon", by R. K. Graupner, Silicon Processing, ASTM STP 804, D. C. Gupta, Ed., American Society for Testing and Materials, 1983, pp. 459-468.
Carver Gary E.
Koos Gregory L.
Michalski John D.
Anderson R. B.
AT&T Bell Laboratories
Pham Hoa Q.
Rosenberger Richard A.
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