Process for fabricating a substrate of the SOI type with reduced roughness and uniform thickness

Available in DE, FR, SG, US

Invention : The invention provides a fabrication process which makes it possible to obtain a SOI substrate, the thin silicon active layer of which has surface roughness that is uniform and preferably is as thin as possible, while still having a buried layer of uniform thickness. 

Claim 1 : A process for maintaining uniform oxide layer thickness while minimizing surface roughness when fabricating a silicon on insulator (SOI) substrate, which comprises: 
implanting atomic or ionic species into a semiconductor donor substrate to form a weakened zone therein, with the weakened zone forming a boundary between a thin active layer and a remainder of the donor substrate;
bonding the donor substrate to a semiconductor receiver substrate by molecular adhesion, with one of the substrates including a uniform oxide surface layer that is present between the donor substrate and the receiver substrate at a certain thickness as a buried oxide layer after bonding;
detaching the remainder of the donor substrate along the weakened zone to obtain a SOI substrate comprising the receiver substrate, the oxide layer and the thin active layer, wherein the thin active layer has an exposed surface and a thickness of 150 nanometers or less;
thermally annealing the thin active layer for at least 10 minutes in a gaseous atmosphere containing hydrogen, argon or both at a temperature of at least 950° C. but not exceeding 1100° C. to avoid a reduction in the uniform thickness of the oxide layer due to dissolution and to provide the buried oxide layer with a thickness of 50 nanometers or less and a thickness uniformity of 1.8 nm or better; and minimizing roughness of the exposed surface of the thin active layer by avoiding formation of dense zones adjacent the thin active layer in conjunction with the annealing,
wherein the formation of the dense zones is avoided by conducting the implantation as a co-implantation of two different atomic species or by initiating the detaching by mechanical action along the weakened zone.


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