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Measurement of Transverse Homogeneity of Electrically Active Impurity Distribution

IP.com Disclosure Number: IPCOM000092717D
Original Publication Date: 1967-Feb-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Fischer, GR: AUTHOR [+2]

Abstract

Variations in the radial distribution of electrically active impurities in elemental semiconductor single crystals are of importance. This is due to the resulting variations in bulk resistivity of transve rse slices subsequently proce ssed from them. These variations have adverse effects on the uniformity and reproducibility of the electrical characteristics of devices fabricated from the material.

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Measurement of Transverse Homogeneity of Electrically Active Impurity Distribution

Variations in the radial distribution of electrically active impurities in elemental semiconductor single crystals are of importance. This is due to the resulting variations in bulk resistivity of transve rse slices subsequently proce ssed from them. These variations have adverse effects on the uniformity and reproducibility of the electrical characteristics of devices fabricated from the material.

Present methods of determination of this radial impurity distribution are by two-probe and four-probe resistivity measurements on transverse test slices taken from the monocrystal in question. See ASTM Tentative Method of Test F43-64T. See also ASTM Proposed Tentative Methods of Test for Bulk Resistivity Variation, Sixth Draft, Feb. 10, 1966.

The determination of axial resistivity profile s of silicon monocrystals utilizing either the two-probe or the four-probe method has been widely practiced for about a decade. This is particularly true of bulk silicon producers whose major bulk monocrystal product is produced by floating zone techniques.

This system essentially comprises a setup for determination of axial resistivity profile s of bulk monocrystals by the two-probe method as commonly practiced and described in ASTM Tentative Methods of Test F43-64T. The probe head used for the voltage measurement, however, is a four-probe, in-line array. During operation of the apparatus, the four probes are placed in contact with the outside of the crystal. The placing is such that the line of the probes is parallel to the longitudinal centerline of the crystal and is located at the axial position desired.

The probes remain in contact until all readings are made to insure minimum measurement variation as a result of repositioning. With the crystal end contacts disconnected, first, a four-probe reading is taken followed by a two-probe reading. During the latter, current is pass...