FINISHING METHOD FOR MANUFACTURING SUBSTRATES IN THE FIELD OF ELECTRONICS
The invention relates to a method for finishing the surface of semiconducting substrate that has a set of layers and a useful semiconducting layer on at least one of the faces of the substrate, wherein the useful layer has a rough free surface. The method smoothes out the rough free surface of the useful layer by creating a protective layer covering the surface of the useful layer with a thickness 1 to 3 times larger than the peak-to-valley distance of the surface of the useful layer, at least one polishing-oxidation sequence that includes the successive steps of polishing the surface of the protective layer, with the polishing being adjusted so as not to attack the useful layer, and performing a thermal oxidation with supply of oxygen gas of the substrate in order to transform a portion of the useful layer into an oxide layer and reduce the roughness of the surface of the useful layer.
1 .- 12 . (canceled)
13 . A method for finishing the surface of a semiconductor substrate having top and bottom faces and comprising a set of layers with a useful semiconductor layer on at least one of the faces, wherein the useful layer has a rough surface, which method comprises smoothing out the rough surface of the useful layer by:
creating a protective layer covering the rough surface of the useful layer with the protective layer having a thickness that is 1 to 3 times larger than the peak-to-valley distance profile of the rough surface of the useful layer; and
conducting at least one polishing-oxidation sequence which comprises:
polishing the protective layer without attacking the useful layer, and
performing a thermal oxidation with oxygen in order to transform a portion of the useful layer into an oxide layer to thus reduce the roughness of the surface of the useful layer.
14 . The method according to claim 13 , wherein the protective layer comprises an oxide.
15 . The method according to claim 14 , wherein the oxide is deposited by PECVD (Plasma Enhanced Chemical Vapor Deposition) or LPCVD (Low Pressure Chemical Vapor Deposition).
16 . The method according to claim 14 , wherein the oxide is provided by thermal oxidation with oxygen.
17 . The method according to claim 13 , wherein the protective layer comprises a nitride.
18 . The method according to claim 17 , wherein the nitride is deposited by PECVD (Plasma Enhanced Chemical Vapor Deposition) or LPCVD (Low Pressure Chemical Vapor Deposition).
19 . The method according to claim 17 , wherein the nitride is provided by thermal nitridation with nitrogen.
20 . The method according to claim 13 , wherein the polishing is a selective polishing of only the protective layer such that the peaks of the useful layer can be exposed.
21 . The method according to claim 13 , wherein the polishing is a non-selective polishing conducted in a manner so as to only remove part of the protective layer without exposing the useful layer.
22 . The method according to claim 13 , wherein the protective layer is formed at a thickness that is about 1.8 times larger than the peak-to-valley distance of the rough surface of the useful layer.
23 . The method according to claim 13 , wherein the useful layer comprises silicon or germanium.
24 . The method according to claim 13 , wherein the useful layer comprises germanium, and oxide layer is a germanium oxide layer formed by thermal oxidation of the useful layer at a temperature between 450 and 5 50 ° C.
25 . The method according to claim 24 , wherein the polishing is non-aqueous polishing or dry polishing.
26 . The method according to claim 13 , wherein the useful layer comprises silicon, and the oxide layer is a silicon oxide layer formed by wet thermal oxidation at a temperature of less than 600° C.