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Measuring Resistivity

IP.com Disclosure Number: IPCOM000075649D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 39K

Publishing Venue

IBM

Related People

Dupnock, AD: AUTHOR [+3]

Abstract

This method for directly measuring the bulk resistivity of an epitaxial semiconductor layer on a monocrystalline semiconductor base, wherein the base has at least two high-conductivity diffused regions, uses a 4-point probe apparatus. In the r-point probe technique a current is introduced into the semiconductor material through two spaced current probes, and the voltage drop across a portion of the wafer between the current probes is measured by two spaced voltage probes.

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Measuring Resistivity

This method for directly measuring the bulk resistivity of an epitaxial semiconductor layer on a monocrystalline semiconductor base, wherein the base has at least two high-conductivity diffused regions, uses a 4-point probe apparatus. In the r-point probe technique a current is introduced into the semiconductor material through two spaced current probes, and the voltage drop across a portion of the wafer between the current probes is measured by two spaced voltage probes.

Referring to the figure, constant-current generator 10 introduces a current flow in epitaxial layer 15 of wafer 12 through current probes 14 and 16. Ammeter 18 is used to measure the current and serves as a check to assure that it remains constant. Potentiometer 20 measures the voltage drop in layer 15 through voltage probes 22 and 24. The loading of the probes is maintained by springs 26, 28, 30, and 32 which support the probes in the proper spacing.

The measuring of the resistivity of an epitaxial layer, supported on a semiconductor wafer, introduces problems not encountered when measuring the bulk resistivity of a wafer or other solid semiconductor object. A semiconductor wafer used in the fabrication of integrated circuit devices, normally contains a large number of buried diffused regions of opposite impurity located at the interface of the epitaxial layer and the wafer. Significant variation in both the current flow paths between the current probes resulting in different current densities at different locations, and also voltage measurements made by the voltage probes, will result from successive measurements when there is a variation of the probe position relative to underlying diffused regions.

Buried diffused regions 34, 36, 38, and 40 among others, not shown, are provided in wafer 12. The respective current and voltage probes are located directly over th...