| 3C-SiC has excellent properties such as a wide bandgap,high electron saturated drift velocity and high thermal conductivity,and has broad prospects in the field of high temperature and high power devices.At present,CVD is used to heteroepitaxially fabricate 3C-SiC films on Si single crystals.However,there are many defects in the obtained films due to lattice mismatch and thermal expansion coefficient differences,which limits it their application in the field of electronic devices.The patterned substrate is a substrate surface pretreatment technology that has been researched in recent years,and can effectively reduce defects in the Si substrate heteroepitaxial 3C-SiC film and improve the film usability.This technique was originally used to study the epitaxial growth of GaN films on sapphire substrates,effectively reducing the dislocation density of GaN epitaxial materials and improving the performance of GaN-based light emitting devices.Affected by this method,the patterned substrate technology is also gradually applied to the growth of 3C-SiC thin films on Si substrates.In this paper,several different pattern substrates were prepared by wet etching or dry etching.3C-SiC was epitaxially grown on a patterned substrate by LPCVD.The epitaxially grown films were characterized by optical microscopy,SEM and XRD.The main research work and conclusions of this paper are as follows:Firstly,the design of the substrate pattern and the specific preparation process of the pattern substrate are introduced.The paper explored three substrate patterns,including squares,stripes,and hexagons.A Si patterned substrate,an SiO2 patterned substrate and a patterned substrate made of a metal mask were prepared using a wet etching and dry etching process,Secondly,the effect of 3C-SiC growth process on SiO2 patterning substrate was studied.The thickness of the oxide layer was 300nm and 500nm.The experimental parameters were vacuum atmosphere at 1200?,H2 atmosphere,mixed atmosphere of H2 and C2H2,and vacuum atmosphere at 1000?,H2 atmosphere.The reasons for the change of the SiO2 mask pattern layer were compared and analyzed.The results show that the SiO2 masking layer is degraded due to the reaction between Si O2 and Si substrate at 1200 °C.The thin(300 nm)oxide layer is seriously degraded and cannot be used as a masking layer.The integrity of the oxide layer with a thickness of 500 nm is better.Then,3C-Si C epitaxial film on a patterned substrate for dry etching was studied.The surface morphology of the polycrystalline thin film on the substrate with a pattern size of 8 ?m is similar to that of the pattern structure.The pattern on the substrate becomes "undulant" due to temperature and growth gas,and the smaller(3?m)substrate pattern is completely etched.The film on the top of the "undulant" pattern is ellipsoidal with a higher film thickness At the bottom of the graph,there is a tendency for the films to coalescence to each other.Finally,the growth behavior of 3C-Si C thin film on wet etching pattern substrate was studied.As a result,the substrate pattern with larger size(>10 ?m)is less affected by the growth process,but it is necessary to grow a thin film with sufficient thickness and the epitaxial layers on the pattern area are combined with each other.The Si O2(500nm)pattern substrate is affected by the growth temperature.Although the surface of the mask pattern layer is complete,but the part is separated from the substrate surface,the film growth process needs to be further optimized in order to suppress the reaction between the oxide layer and the substrate and obtain selective growth 3C-Si C thin film.In addition,studies have been conducted on the growth of 3C-Si C films on a patterned substrate with a metal Al mask.The results show that the Al mask pattern layer has good stability,can inhibit the nucleation of gas phase molecules on the surface,make the polycrystalline thin film grow only in the window area of the Si substrate,and observe the lateral growth of the 3C-Si C thin film. |
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