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Analytical Technique for Probing and Controlling Gas Composition in Chemical Processes

IP.com Disclosure Number: IPCOM000079217D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Fowler, AB: AUTHOR [+3]

Abstract

The figure indicates how Raman scattering may be used to monitor gas reactor composition along the surface of semiconductor wafers, such as silicon. Raman scattering gas analysis is very useful in determining concentration gradients in any reactor, where gas composition may influence the uniformity of the desired product.

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Analytical Technique for Probing and Controlling Gas Composition in Chemical Processes

The figure indicates how Raman scattering may be used to monitor gas reactor composition along the surface of semiconductor wafers, such as silicon. Raman scattering gas analysis is very useful in determining concentration gradients in any reactor, where gas composition may influence the uniformity of the desired product.

In the figure, an rf susceptor is disposed within a transparent square-reactor tube. A semiconductor wafer is disposed on top of the rf susceptor which is heated from an rf source, not shown, which, in turn, raises the temperature of the silicon wafer to a desired value. The square-reactor tube is filled with a gas or gases which are to be monitored in some specific localized region, or to measure composition gradients throughout the reactor tube. Using a laser beam from a laser, advantage is taken of the fact that a very small region in the reactor, less than 1mm/3/ is probed without introducing any perturbing physical probes. This advantage arises because Raman spectroscopy can conveniently be done in a 90 degrees scattering geometry, where the Raman scattered light is detected at or near 90 degrees from the exciting laser beam. Thus, the laser beam, approximately 1mm in diameter, is passed through the wall or window of a square-tube reactor which Raman scatters with molecules all along the beam path.

The Raman scattered light (with wavelength characteristics of the scattering molecules) is collected from a small length of beam (1mm) from a sampled r...