Preparation And Properties Of SiC Films Based On Vapour Deposition Method

Silicon carbide(SiC),as a representative of third-generation semiconductors,has a highly stable crystal structure,which makes it excellent in high temperature and corrosion resistance.In this study,physical vapour deposition by RF magnetron sputtering and high-temperature chemical vapour deposition(HT-CVD)were used to prepare silicon carbide thin films on different process conditions and growth substrates.The analysis of the interfacial mechanism of silicon carbide films grown on heterogeneous substrates was carried out by first principles,providing a reference for the growth of large-size silicon carbide filmsHere,amorphous SiC thin films with AlN as a buffer layer were deposited on glass and Si substrates through RF magnetron sputtering at different RF powers.The influence of the AlN buffer layer thickness on the morphological and the mechanical properties of the composite films was investigated.Results demonstrate that the AlN buffer layer can effectively improve the adhesion strength of SiC thin films,which has increased gradually from 26.78 N to 37.66 N The transmittance of SiC thin films was measured using a UV-Vis-NIR spectrophotometer over a spectral range of 300-1200 nm.The average transmittance of SiC films decreases with increasing RF power,and their optical band gap values have varied from 3.31 eV to 3.50 eV.In the study of silicon carbide thin films deposited by HT-CVD,SiC films were prepared on homogeneous and heterogeneous epitaxial substrates(sintered silicon carbide,single crystal Si and graphite)at deposition temperatures of 1100℃-1500℃ using MTS as the feed gas and H2 as the transport gas.The differences in surface morphology,roughness,structural composition and growth mechanism of SiC films on different substrates were compared and analyzed.The results show that the deposition temperature has a significant effect on the growth of the films,and the SiC films grown on all three substrates exhibit relatively flat and dense surface morphology from 1300℃ to 1400℃.Defects such as reticulation often appear in low temperature,while the deposition of high temperature is prone to generate directional growth.In terms of roughness,SiC films grown on homogeneous epitaxial substrates reach an optimum of 0.690μm at 1400℃,Graphite/SiC films on heterogeneous substrates reach an optimum of 0.928μm at 1300℃ and Si/SiC films at 1200℃ reach an optimum of 0.469μm;The homogeneous epitaxially grown SiC films exhibit a layer-like growth pattern while the heterogeneous epitaxially grown SiC films exhibit an island-like growth pattern.In terms of structural composition,all three types of SiC films on the substrate exhibit diffraction peaks on the(111),(220)and(311)crystal planes at 35.6°,59.9° and 71.7μ respectively,with the single-crystal Si substrate showing no diffraction peaks for other impurities at the deposition temperature of 1100℃-1400℃,and the(111)crystal plane with the highest intensity.The SiC films deposited on Rβ-SiC/SiC substrates exhibit multi-oriented grain growth,with the(220)and(3 11)grain plane diffraction peaks gradually increasing as the deposition temperature increases;the SiC films grown on graphite substrates also exhibit strong(111)growth orientation,but start to exhibit impurity diffraction peaks as the deposition temperature increases to 1500℃.In terms of film hardness,homogeneous epitaxial SiC films are generally harder than heterogeneous epitaxial ones,and the(111)densely packed surfaces exhibit higher hardness valuesIn addition,the adhesion work and interfacial energy of the Si(111)/SiC(111)and graphite(001)/SiC(111)interfaces were calculated by first principles methods.The effects of SiC(111)surface capping by Si atom and the three interfacial atom stacking positions(central,hole and top)on the interfacial properties were investigated.The differences in interfacial properties on heterogeneous substrates were further compared and the results showed that the top-site interfacial stacks have the best interfacial properties in both the Si(111)/SiC(111)and graphite(001)/SiC(111)model systems,with the graphite(001)/SiC(111)interfacial system having the best interfacial properties compared to the Si(111)/SiC(111)system.Graphite(001)/SiC(111)has a larger adhesion work as well as a smaller interfacial energy,indicating that the SiC films deposited on graphite substrates is more stable interfacial configuration in thermodynamics.