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Spectroscopic Determination of Wafer Thickness for Measurement of Interstitial Oxygen by Dispersive Infra-red Spectroscopy

IP.com Disclosure Number: IPCOM000060686D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Harwood, PB: AUTHOR [+2]

Abstract

In the manufacture of semiconductor devices interstitial O2 concentration must be measured during silicon crystal and w development since it affects yields. An invention proposes a method whereby the number of fringes in the absorbance spectrum of an infra-red spectrometer may be used to determine wafer thickness, a necessary step in determining O2 concentration.

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Spectroscopic Determination of Wafer Thickness for Measurement of Interstitial Oxygen by Dispersive Infra-red Spectroscopy

In the manufacture of semiconductor devices interstitial O2 concentration must be measured during silicon crystal and w development since it affects yields. An invention proposes a method whereby the number of fringes in the absorbance spectrum of an infra-red spectrometer may be used to determine wafer thickness, a necessary step in determining O2 concentration.

Conventional infra-red absorbance techniques for measurement of interstitial O2 in silicon require either measurement of absorbance peak height at a characteristic silicon band or independent measurement of thickness, such as by means of a capacitance gauge. The former is used primarily for Fourier transform spectrometers with the collection of the necessary band spectrum being a time- consuming operation on a dispersive spectrometer. The latter requires an additional operation beyond collection of the spectrum and generally is performed at a different work station.

A simple method to make the measurements has been devised whereby it is possible to make use of the interference fringes observed in a high resolution spectrum of a polished plane- parallel silicon wafer for calculation of thickness. The light intensity measured at the absorption peak of interest is related to reflective and transmission properties of silicon.

If P complete fringes are observed in a wave number interval o...