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Porosity Determinations in Buried and Surface Layers of Porous Silicon

Published online by Cambridge University Press:  28 February 2011

Terry R. Guilinger
Affiliation:
Sandia National Laboratories, Albuquerque, New Mexico 87185
Michael J. Kelly
Affiliation:
Sandia National Laboratories, Albuquerque, New Mexico 87185
Sylvia S. Tsao
Affiliation:
Sandia National Laboratories, Albuquerque, New Mexico 87185
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Abstract

Gravimetric techniques offer a convenient and accurate method of determining surface layer porosity in both n- and p-type porous silicon (PS). Porosity of the PS affects its volume expansion on oxidation and the insulating properties of the resulting oxide. Optimal porosity (ca. 55%) yields fully dense, insulating oxides with minimal expansion-induced stresses. Two factors affect the porosity: chemical dissolution of PS by the anodization electrolyte, and oxidation of the PS to produce a native oxide on the surface. Buried layer porosities cannot normally be measured by gravimetric techniques unless the volume of the buried layer is large enough to yield a measurable weight change on anodization. We therefore used a form of Faraday's Law to determine buried layer porosities and determined that they can be correlated with porosities of surface layers formed under identical conditions.

Type
Research Article
Copyright
Copyright © Materials Research Society 1988

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