Abstract: The method is for forming porous silicon in a silicon substrate, in particular for improving the quality factor of an inductive circuit produced on a silicon semiconductor wafer which also incorporates integrated transistors. The rear face of the wafer, already incorporating the transistors and the inductive circuit on its front face, is placed in contact with an acid electrolyte containing hydrofluoric acid and at least one other acid. An anodic oxidation of the silicon of the wafer at the rear face is carried out so as to convert this silicon into porous silicon over a predetermined height from the rear face which is in contact with the electrolyte.

Abstract: The method consists in establishing the ion bombardment parameters, in varying a regulation parameter in order to initiate deposition, in measuring at each instant the total pressure drop within the vacuum chamber with respect to the initial pressure and in controlling the total pressure drop by controllably varying the regulation parameter.