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Epitaxy Temperature Measurement by Impurity Profile Redistribution Calibration

IP.com Disclosure Number: IPCOM000049574D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 28K

Publishing Venue

IBM

Related People

Depin, JP: AUTHOR [+4]

Abstract

Present temperature measurements in epitaxy reactors failed to provide the average temperature of the wafers during a complete thermal processing step.

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Epitaxy Temperature Measurement by Impurity Profile Redistribution Calibration

Present temperature measurements in epitaxy reactors failed to provide the average temperature of the wafers during a complete thermal processing step.

In standard epitaxial and silicon nitride deposition equipment, like the AMC 7600 manufactured by Applied Material Inc., the temperature measurement is performed through 3 photodiodes located inside the Si-C coated graphite susceptor. However, this measurement is more representative of the susceptor temperature than of the wafer temperature.

A first improvement involving a thermocouple, which allows the instantaneous temperature of the wafer, is described in the IBM Technical Disclosure Bulletin 23, 1061-1062 (August 1980).

Although this improvement has demonstrated its usefulness mainly with respect to the problem of the warpage of large diameter wafers, it does not reflect the actual thermal variations of the wafers, since thermal inertia is not taken into account.

An another improvement, which will be thereafter described, is based on the discovery that an impurity profile redistribution is perfectly representative of the total wafer heat treatment.

The resulting diffusion profile of either the subcollector or emitter region doped with arsenic is of the abrupt type following closely a square root of Dt redistribution law, because it is well known that for a determined surface concentration C(s) the diffusion depth xj is proportional to the square root of Dt. In this relation, t is the diffusion time and D is the diffusion coefficient given by D equals Do exp -Ea/kT in which Do and k are constants, T is the temperature in ...