Purpose. Preparation of epitaxial SiC films by converting nanoporous Si into a SiC film by annealing in an atmosphere of a mixture of carbon monoxide (CO) and silane (SiH4) gases in a special installation.
Specifications. SiC films must have the following characteristics: – SiC film thickness, nm, no more than 2.0; – root-mean-square roughness of SiC films, nm, not more than 50.0; – peaks of photoluminescence spectra, nm, 355.0-650.0; – half-width of the vibration curve in the (111) plane, arcsec, no more than 200.0; – half-width of the oscillation curve in the plane (311), arcsec, no more than 300.0
Application area. Solar energy, micro- and optoelectronics
Advantages. The production of SiC/porous-Si/Si (111) heterostructures occurs due to the transformation of the mesoporous surface of the substrate into a silicon carbide film during solid-phase epitaxy with the formation of a new porous layer. The fundamental difference between the method of chemical substitution of atoms and others is that the SiC layer is not grown on top of the Si surface, as usual, but is formed directly in the bulk of the silicon substrate.
Technical and economic effect. Wide-gap semiconductors GaN, AlN, Ga2O3 and ZnO are the most attractive materials for creating LEDs, laser diodes, solar cells, and field-effect transistors. The most promising substrate for these materials is SiC. However, the commercial cost of producing SiC single crystals is very high. By creating single-crystalline SiC films with a low dislocation density on the surface of Si wafers, this cost can be reduced by 9-12%.
Description. The essence of the technology is to create physical and technological conditions for obtaining a SiC/porous-Si/Si (111) heterostructure by converting the mesoporated surface of a silicon substrate into a silicon carbide film during solid-phase epitaxy at a processing temperature of 1290°C. When annealing in columns of nanoporous silicon, silicon atoms are replaced by carbon atoms and a SiC molecule and a silicon vacancy are formed. As a result, the nanoporous layer turns into a film of silicon carbide, and under the resulting film of silicon carbide, silicon vacancies are formed, which combine together and form pores. Thus, by setting the thickness of the porous layer, the thickness of the silicon carbide film is specified. Pores form under the silicon carbide film, which lead to a decrease in mechanical stresses in the film when there are large differences between the lattice parameters of the film and the substrate. A method for obtaining a SiC/porous-Si/Si (111) heterostructure is proposed, which includes the following steps: 1. obtaining a porous silicon surface by electrochemical etching of single-crystal Si wafers with a diagonal of 100 mm, doped with boron/phosphorus with an electrical resistivity of 1-10, thickness 500± 25 µm, dislocation density <100 cm-2; 2. obtaining a SiC film on the porous-Si/Si (111) surface by annealing in an atmosphere of a mixture of carbon monoxide (CO) and silane (SiH4) gases in a special installation at a temperature of 1290°C, for 20 minutes, the total pressure of the gas mixture is 53 Po.