The kinetics and mechanism of oxide layer formation from porous silicon formed on p-Si substrates

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Abstract
The formation of oxide layers from porous silicon layers formed on P substrates which present different and well‐controlled porous textures is studied in detail. It is shown that the overall process leading to oxides with properties similar to standard thermal oxides consists of two steps: the oxidation of silicon in the porous layer and the densification of silica. The first step does not depend upon the initial texture of the layer, but is mostly determined by the porosity of the sample and the temperature of the oxidation sequence. The second step, oxide densification, which takes place at temperatures higher than 1000 °C, is very sensitive to the porous texture of the layer, the densification times increasing sharply with the average pore size. The densification process has a high activation energy, which can be related to the activation energy for the viscous flow of silica.