Study On The Oxidation Mechanism Of Silicon Carbide And The Epitaxial Growth Of Graphene Under The Action Of Atmospheric Plasma

Single crystal SiC is a wide band gap semiconductor material with excellent performance,and it is gaining wider and wider applications in the manufacture of hightemperature,high-frequency,and high-power electronic devices.Growing an insulating oxide layer on the surface of SiC is a key step in manufacturing SiC-based devices.The quality of the oxide layer directly determines the performance of the device.In addition,graphene can epitaxially grow on the SiC substrate based on the thermal decomposition of SiC,which is of vital importance to promote the applications of graphene and SiC.Traditional processes,however,still lack in improving the interface characteristics of the oxide layer and the key properties of graphene,such as the area,quality,and layer uniformity.To begin with,this study reveals the oxidation kinetics of SiC at ultra-high temperatures.Then,it demonstrates the oxidation process of SiC,the epitaxial growth of graphene,and the corresponding mechanisms in detail under the action of plasma,using the advanced atmospheric ICP plasma processing technology.The main contents and conclusions are as follows:Firstly,this study investigates the role of oxygen in the surface kinetics of single crystal SiC at ultra-high temperatures.By oxidizing SiC under different oxygen concentration conditions at 1500 ?,it is found that the oxygen concentration can strongly manipulate the competitive growth of thermal oxidation SiO₂?TO-SiO₂?and thermal chemical vapor deposition SiO₂?TCVD-SiO₂?,and the low oxygen concentration favors the formation of TCVD-SiO₂.In this study,the differences between TO-SiO₂ and TCVD-SiO₂ in the domain morphology,crystal quality,interface structure,and growth kinetics are systemically analyzed.The layer-by-layer oxidation mechanism of SiC and the SiC atomic steps transverse evolution mechanism are proposed for TO-SiO₂ growth and TCVD-SiO₂ growth,respectively.Furthermore,based on the Reax FF reactive molecular dynamics simulation results,it is demonstrated that the decrease in oxygen concentration can promote the growth kinetics of SiO₂ on single crystal SiC from being dominated by thermal oxidation to being dominated by thermal CVD.Secondly,this study reveals the oxidation behavior of SiC under the action of ICP plasma,and advances a non-subtractive polishing technology for SiC accordingly.Based on the oxidation results of SiC under the conditions of different radio frequency input powers,irradiation times,and oxygen concentrations,it is discovered that SiO₂ nanoparticles grow along the atomic step-terrace structure of the SiC substrate;the generated oxide distributes layer by layer;the step is oxidized preferentially than the terrace.By increasing the input power and controlling the total amount of oxygen in the reaction system,a sliced surface SiC sample with a Sa roughness about 70 nm is successfully polished to an atomic ultra-smooth level with a Sa roughness below 0.2 nm,and the regularly arranged atomic step-terrace structure can be detected on the polished surface.According to the experimental results,a polishing mechanism,whose key point is the closed loop reaction composed of the thermal decomposition of SiC,the plasma oxidation of SiC,and the reaction between the oxide layer and the carbon buffer layer,is proposed.Thirdly,this study demonstrates the feasibility of the epitaxial growth of graphene on the SiC substrate by ICP plasma irradiation.Owing to the high temperature characteristic of ICP plasma and the shielding effect of gas flow on the atmosphere during the close-range plasma irradiation,the epitaxial growth of graphene on the SiC surface is achieved.This study reveals the formation,expansion,and overlap processes of hexagonal pits as well as the following growth process of graphene flakes on the substrate surface.Ultimately,considering the existing shortcomings of the current plasma equipment,a new ICP plasma equipment with a gas displacement chamber is designed.