Process for buried localized oxidation of a silicon substrate and corresponding integrated circuit

Claim 1

A process for buried localized oxidation of a silicon substrate, which consists, successively: in performing a) a sealing on the free area of the said substrate, by a first nitriding, by controlled growth of a layer of silicon nitride forming at least one surface layer in order to ensure the sealing of said free area, forming a horizontal interface, this surface layer being obtained by diffusion of nitrogenous species from a reactive atmosphere into the surface layers of silicon and having a thickness not exceeding 5 nm, in performing b), following an appropriate masking stage, the etching into said silicon substrate and said silicon nitride layer, of a trench intended to receive said buried localized oxidation, the depth of the trench and the thickness of the localized oxide determining the difference in alignment between the free area of the buried oxide and that of the silicon substrate, in performing c) on the free area of said trench, by a second nitriding, a sealing by growing a silicon nitride layer in order to ensure the sealing of the walls of said trench, in performing d), on at least a part of the bottom surfaces of said trench, an etching of the silicon nitride layer obtained by said second nitriding, in order to uncover the material of said silicon substrate, in performing e) a localized oxidation of said material to produce the buried oxidation of said substrate in the trench.