Research On Hardness And Thermal Conductivity Of Silicon Carbide-based Semiconductor Materials

As a typical material in third-generation semiconductors,silicon carbide has gradually occupied a larger application field and market share in the semiconductor field due to its superior properties,such as high hardness,high thermal conductivity,and high band gap.The growth of silicon carbide single crystals has relatively mature technical theories and equipment support,such as liquid phase method,high temperature chemical vapor deposition(HTCVD)and physical vapor transport(PVT).At this stage,the PVT method is currently the most studied and most mature technology for SiC single crystal growth.The processing of silicon carbide materials,such as cutting,grinding and polishing,is an important step before the material is applied.In the process of processing,hardness is a physical characteristic that needs to be emphatically referenced,but the current hardness value of silicon carbide is basically a value or range in general,and there is no detailed distinction.In the industrialization process,the ratio of grinding ingredients and the processing time need to establish a relationship with the hardness value.This article uses the nanoindenter to test and explore the relevant parameters that may have an impact on silicon carbide.It is found that the microtubules,crystal forms,and the junctions of the crystal forms have no significant effect on the hardness;the hardness of silicon carbide is anisotropic,the hardness of the silicon surface is higher than that of the carbon surface,and the hardness of the A surface is less than that of the silicon surface.The effect of doping on the hardness of silicon carbide was explored,and it was found that there is a positive correlation between the concentration of nitrogen doping and the hardness,and the doping of vanadium will reduce the hardness of silicon carbide.Because hardness is a relatively complex physical quantity and a comprehensive characterization quantity,it is difficult to establish a fully consistent model for the micromanagement theory of hardness.However,the discussion on hardness theory has not stopped.Teter et al.found that there is a certain proportional relationship between the hardness value of the material and the shear modulus(G)of the material Hv=0.151G,which has become a popular theory now.The first-principles calculations are now an important theoretical basis in computational materials science.The paper uses MS software and VASP software to calculate the elastic modulus of silicon carbide,and finds that the elastic modulus of doped crystals is lower than that of undoped crystals.Compared with hardness,the theoretical principles of silicon carbide thermal conductivity are much more mature.For semiconductor materials,the total thermal conductivity ? is the sum of two components,?-?L+?C;where ?L and ?C are respectively The contribution of lattice and carriers to thermal conductivity.Due to the crystal structure of silicon carbide,the heat transfer distance is different in different directions,and doping affects the crystal lattice and so on,thereby affecting the thermal conductivity.In this thesis,the anisotropy of the thermal conductivity of silicon carbide is explored,and it is found that the thermal conductivity of the a-axis sample is the same as that of the "m" axis,and it is significantly higher than the c-axis.Doping vanadium will reduce the thermal conductivity,and high temperature treatment can increase the thermal conductivity of vanadium-doped crystals.High temperature is the "killer"of devices,and timely heat dissipation plays an important role in device safety.If we want to continue to improve the heat conduction of silicon carbide substrate devices,we can epitaxially grow diamond films with higher thermal conductivity.In this thesis,preliminary research on this technology has been carried out through single-layer,double-layer,and groove-cutting methods.The experimental results show that the double-layer composite method improves the heat transfer performance of the material.COMSOL finite element simulation software is easy to use,powerful database,rich physical field and other advantages,which is convenient for heat transfer related simulations.This paper uses the solid heat transfer module of the software to perform qualitative heat transfer analysis of composite materials.It is found that the single-layer,double-layer and grooved models will improve the heat transfer performance of the composite material,while the graphite phase will significantly reduce the thermal conductivity.