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Thickness Measurement of Composite SiO(2) and Si(3)N(4)

IP.com Disclosure Number: IPCOM000079024D
Original Publication Date: 1973-Apr-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

DiGiacomo, G: AUTHOR

Abstract

The electrical characteristics of field-effect transistor devices are dependent on the thickness of the nitride-oxide composite gate insulator.

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Thickness Measurement of Composite SiO(2) and Si(3)N(4)

The electrical characteristics of field-effect transistor devices are dependent on the thickness of the nitride-oxide composite gate insulator.

The present technique utilizes an electron microprobe for thickness measurement. As illustrated in the figure, an electron beam is focused at the normal to the composite Si(3)N(4)-SiO(2) film which is disposed atop silicon substrate 5. Initially, the X-ray intensity of the oxygen in the SiO(2) film 4 is measured at 10 Kv, in order to determine the thickness of film 4 without measuring the nitrogen in the nitride layer 3. The nitrogen is excluded because of its low detectability which is inadequate to meet precise requirements. The thickness of the Si(3)N(4) layer 3 is derived by an empirical relationship, which expresses the thickness of layer 3 in terms of the X-ray radiation intensity of the silicon and oxygen in layer 4.

In the process, the thickness of oxide layer 4 is obtained from a calibration curve determined with SiO(2) standards, using X-ray intensities measured at 10 Kv. For these curves, there is no Si(3)N(4) overlay. At this voltage, the oxygen X-ray intensity is relatively independent of the Si(3)N(4) thickness.

Having determined the SiO(2) thickness, the oxygen and silicon X-ray intensities I are measured at 2.5 Kv from the unknown samples and from samples having known thicknesses. These values are substituted in an empirical equation to find the thick...