Process for the transfer of a thin film comprising an inclusion creation step
A process for transferring a thin film includes forming a layer of inclusions to create traps for gaseous compounds. The inclusions can be in the form of one or more implanted regions that function as confinement layers configured to trap implanted species. Further, the inclusions can be in the form of one or more layers deposited by a chemical vapor deposition, epitaxial growth, ion sputtering, or a stressed region or layer formed by any of the aforementioned processes. The inclusions can also be a region formed by heat treatment of an initial support or by heat treatment of a layer formed by any of the aforementioned processes, or by etching cavities in a layer. In a subsequent step, gaseous compounds are introduced into the layer of inclusions to form micro-cavities that form a fracture plane along which the thin film can be separated from a remainder of the substrate.
1. A process for forming a thin film from a substrate comprising the steps of:
(a) forming a first film on a surface of the substrate by epitaxial deposition, the first film doped by boron to form a layer of inclusions extending parallel to the surface of the substrate, wherein the layer of inclusions forms a gaseous compound trap zone and, subsequently, forming a second film doped by boron on the first film by epitaxial deposition, wherein the second film has a boron concentration that is less than the first film;
(b) after step (a), implanting a dose of gaseous compounds into the gaseous compound trap zone, wherein the dose of gaseous compounds is sufficient to cause formation of micro-cavities in a fracture plane including the gaseous compound trap zone and along which the thin film can be separated from the remainder of the substrate, the gaseous compound trap zone substantially confining the gaseous compounds therein;
(c) separating the thin film from the substrate along the fracture plane and thereafter recovering the thin film.
2. The process for forming a thin film according to claim 1 , wherein forming the first film comprises forming a silicon film.
3. The process for forming a thin film according to claim 1 , wherein epitaxial deposition of the first film comprises epitaxial deposition having a boron concentration at 10 14 to 10 20 atoms/cm 3 .
4. The process for forming a thin film according to claim 3 , wherein step a) comprises the epitaxial deposition, on the substrate, of the first film doped by boron with a concentration of about 1×10 19 atoms/cm 3 .
5. The process for forming a thin film according to claim 3 wherein epitaxial deposition of the second film comprises epitaxial deposition having a boron concentration of about 5×10 15 atoms/cm 3 .
6. The process for forming a thin film according to claim 1 , wherein step a) further comprises coating the second film with an oxide.
7. The process for forming a thin film according to claim 6 , wherein coating the second film with an oxide comprises coating with SiO 2 .
8. The process for forming a thin film according to claim 1 , wherein forming the first film comprises forming a film having a thickness of about 50 nm.
9. The process for forming a thin film according to claim 1 , wherein recovering the thin film comprises placing a support in intimate contact with the substrate, such that the thin film bonds to the support, thereby transferring the thin film from the substrate to the support.
10. The process for forming a thin film according to claim 9 further comprising bonding the substrate to a support in the absence of a pre-heating step.
11. The process for forming a thin film according to claim 1 , wherein epitaxial deposition of the first film comprises forming a material having a parametric crystalline mismatch with adjacent regions of the substrate.
12. The process for forming a thin film according to claim 1 , wherein the gaseous compound trap zone confines the gaseous compounds within a thin, disturbed layer that is thinner than that obtained by introducing a dose of gaseous compounds in the absence of the gaseous compound trap zone.
13. The process for forming a thin film according to claim 1 , wherein implanting gaseous compounds comprises implanting hydrogen.
14. The process for forming a thin film according to claim 1 , wherein forming the first film and forming second film comprise forming silicon films.