Effect of the content of hydrogen fluoride in an etchant on the formation of nanopores in silicon during electrolytic etching.

The effect of the HF content on the formation of nanopores in silicon during electrochemical etching was studied. Nanoporous silicon layers were established to be formed only when hydrogen fluoride content in etchants (initial HF content: 49 wt %) was higher than 10-12 vol %. The mass and charge balance of the electrolytic etching of silicon was calculated, and the change in charge number of reaction (effective silicon valence) was determined depending on the HF content. The obtained data were used to propose a silicon etching model with the formation of SiF and nanoporous silicon (where nanopores were formed due to the action of predominantly (HF) ions). [ABSTRACT FROM AUTHOR]