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Proceedings Paper

Semiconductor Processing Technique Based On Faraday Rotation Measurement Using A CO[sub]2[/sub] Laser
Author(s): Syed Razi; George A Tanton
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Paper Abstract

A non-destructive technique for processing semiconductor material based on Faraday Rotation (FR) measure-ment has been developed and successfully utilized for evaluation of single crystal Cadmium Sulfide (CdS) wafers. We have extended the technique to the infrared region of the spectrum by utilizing a CO2 laser, thus significantly enhancing wafer mapping capability of the technique. Since homogeneity becomes a serious problem for large size wafers, considerable cost savings are realized if the wafer is screened prior to array fabrication. CdS Schottky barrier detectors are presently used in the two-color STINGER-POST missile system. In the band edge region, FR was found to vary as λ-2, where X is the wavelength of the incident radiation, as predicted by the theory for interband transitions. In the infrared, e.g., at 10.6 microns, FR is primarily due to free carriers and varies as λ 2. Free carrier concentration calculated from FR measurements agrees well with results obtained by Hall measurements. Advantages of the FR method are: 1) no contacts need be alloyed, hence no material contamination, 2) surface preparation such as etching/polishing is not required, 3) it is a rapid technique and does not require a skilled operator, and 4) by the use of the CO2 laser, auto-mated wafer mapping is possible. This technique, used here for CdS, is applicable for any semiconductor material where rapid measurement of carrier concentration and a determination of material homogeneity is desired. Development of a self-contained, automated and computer controlled wafer mapping system based on carrier concentration measurement by FR will be described. Results obtained for CdS wafers will be presented

Paper Details

Date Published: 23 October 1986
PDF: 7 pages
Proc. SPIE 0665, Optical Techniques for Industrial Inspection, (23 October 1986); doi: 10.1117/12.938776
Show Author Affiliations
Syed Razi, General Dynamics (United States)
George A Tanton, U.S. Army Missile Command (United States)

Published in SPIE Proceedings Vol. 0665:
Optical Techniques for Industrial Inspection
Paolo G. Cielo, Editor(s)

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