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Contactless In-Situ Monitoring of Thin Films During Processing by Pulsed Photothermal Bending Modes

IP.com Disclosure Number: IPCOM000102689D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 98K

Publishing Venue

IBM

Related People

Dreyfus, RW: AUTHOR [+3]

Abstract

It has previously been shown (von Gutfeld et al in Applied Physics Letters, Vol. 49, 1059 (1986)) that the surface of materials receiving focused pulsed laser light deforms locally. The major deformation, due to bending modes, is considerably larger than that obtained from thermoelastic expansion. This deformation can be monitored and measured by the angular deflection from a second laser beam incident on the sample and reflected into a position-sensitive detector. The degree of bending depends on several parameters, especially the amount of light absorbed and the geometry of the sample.

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Contactless In-Situ Monitoring of Thin Films During Processing by Pulsed Photothermal Bending Modes

       It has previously been shown (von Gutfeld et al in
Applied Physics Letters, Vol. 49, 1059 (1986)) that the surface of
materials receiving focused pulsed laser light deforms locally.  The
major deformation, due to bending modes, is considerably larger than
that obtained from thermoelastic expansion.  This deformation can be
monitored and measured by the angular deflection from a second laser
beam incident on the sample and reflected into a position-sensitive
detector.  The degree of bending depends on several parameters,
especially the amount of light absorbed and the geometry of the
sample.

      What is proposed in this article is the use of this effect as a
diagnostic tool to make in-situ measurements of film thickness on
samples during processing.  For example, changes in the thickness of
an SiO2 layer on a silicon wafer during RIE etching can be monitored.
This is very difficult, if not impossible, to achieve using other
present-day technologies.  The thickness of layers being deposited
can then be monitored in real time, thereby providing information as
to when the desired thickness has been reached during the deposition
step.  The proposed technique will also permit the measure of gaseous
adlayers that become physi- or chemisorbed to a silicon wafer surface
during processing.

      The arrangement for undertaking the proposed measurements is
...