Method of producing integrated silicon structures on isolated islets of the substrate

Claim 1

A method for forming monocrystalline silicon islets isolated from the substrate on an integrated circuit, comprising the following steps: a. provision of a monocrystalline semi conductor wafer which is coated, possibly after thin oxidization, with a first layer of silicon nitride, b. etching the nitride with a pattern leaving zones of small width (FIG. 1), c. vertical hollowing out of the monocrystalline silicon outside the places protected by the nitride, so that monocrystalline silicon islets remain whose upper surface is coated with nitride (FIG. 2), d. deposition of the second silicon nitride layer which covers the surface of the wafer as well as the sides of the islet and the first nitride layer (FIG. 3), e. vertical anisotropic etchinq of the nitride until the silicon is bared outside the islets, the nitride of the second layer then remaining on the sides of the islets and that of the first layer remaining on the top of the islets (FIG. 4), f. isotropic etching of the bared silicon outside the islets protected by the nitride, this etching extending partially under the islets (FIG. 5), g. thick thermal oxidization of the wafer for a time sufficient for a silicon oxide layer to be formed extending completely under the islets and isolating them dielectrically from this substrate (FIG. 6), h. the nitride layer remaining on the islets is removed.

Claim 2

A method for forming monocrystalline silicon islets isolated from the substrate on an integrated circuit, comprising the following steps: a. provision of a monocrystalline semi conductor wafer which is coated, possibly after thin oxidization, with a first layer of silicon nitride, b. etching the nitride with a pattern leaving zones of small width (FIG. 1), c. vertical hollowing out of the monocrystalline silicon outside the places protected by the nitride, so that monocrystalline silicon islets remain whose upper surface is coated with nitride (FIG. 2), d. deposition of the second silicon nitride layer which covers the surface of the wafer as well as the sides of the islet and the first nitride layer (FIG. 3), e. vertical anisotropic etchinq of the nitride until the silicon is bared outside the islets, the nitride of the second layer then remaining on the sides of the islets and that of the first layer remaining on the top of the islets (FIG. 4), f. isotropic etching of the bared silicon outside the islets protected by the nitride, this etching extending partially under the islets (FIG. 5), g. thick thermal oxidization of the wafer for a time sufficient for a silicon oxide layer to be formed extending completely under the islets and isolating them dielectrically from this substrate (FIG. 6), h. the nitride layer remaining on the islets is removed.