The Large-size Homoepitaxial Growth Of 4H-SiC And Device Verification

The"14th Five-Year Plan"nominates integrated circuits to focus on wide-bandgap semiconductors such as silicon carbide and gallium nitride.Compared with Si and Ga As,the advantage of silicon carbide(SiC)material is that it has a wide band gap(3?3.3e V)and a high breakdown electric field(2.5?5MV/cm),high electron drift speed(2×10⁷cm/s)and high thermal conductivity(4.5?4.9W/cm?),The devices made of SiC are small in size but powerful in function.Silicon carbide epitaxial wafers are the basis for the preparation of silicon carbide power devices.This article uses the latest generation of Aixtron G5 WW equipment,Based on the TCS+C₃H₈+H₂ growth system,a systematic study on the homoepitaxial growth technology of large-size,multi-chip 4H-SiC has been carried out.The main research results are as follows:1.The 6-inch 4H-SiC epitaxial growth process was studied.When the C/Si ratio is 1.2,the influence of the TCS flow rate on the C/Si ratio is studied.The growth rate reached 24um/h when the TCS flow was 340sccm.When the TCS flow rate is maintained at 340sccm,it is found that the growth rate will decrease when the C/Si decreases.In this experiment,the uniformity was adjusted by optimizing the C/Si ratio,optimizing the temperature field,gas flow field and other parameters,and realized the SiC epitaxial wafer thickness unevenness<2%,concentration unevenness<3%.Research on the surface morphology found that even if C/Si is 1.3 and the TCS flow rate reaches 340sccm under the growth system of TCS+C₃H₈+H₂,the surface RMS is only about 0.2nm.The surface morphology of the 4H-SiC epitaxial layer is good.No silicon droplets were found on the surface of the layer.Finally,the influence of H₂ etching temperature on the scratches of the substrate is studied.Optimizing the etching temperature can eliminate the scratches introduced by the substrate during the CMP stage.2.Established a model of the formation mechanism of triangle defects and basal plane dislocations.Triangular defects have a variety of morphologies,and the origins of various morphologies are different.In this paper,optical microscope,Raman scattering and other characterization methods are used to analyze the various morphology triangles on 4H-SiC epitaxial wafers obtained under the TCS+C₃H₈+H₂ system.The structure and generation mechanism of defects have been studied,It is found that all triangle defects are caused by 2D,and the formation mechanism of headless triangle defects and inverted pyramid triangle defects is established according to the different growth modes.Through chemical etching,optical microscopy and other characterization methods,the formation mechanism of arrayed BPD was established.These works laid the foundation for further research and reduction of4H-SiC defect density.3.Perform X-RD detection and Raman scattering on the 4H-SiC epitaxial wafer we finally obtained,and confirm that the SiC epitaxial layer we grow is a uniform 4H-SiC crystal;(0004)The half-width of the rocking spectrum of the surface is 21.1859arcsec,which proves that the epitaxial layer crystal quality is very good;the surface roughness measured by the atomic force microscope is only 0.228nm,and 3D AFM is used to prove that the 4H-SiC epitaxial layer surface has atomic steps surface.The doping uniformity measured by non-contact C-V is 2.78%.Using FTIR film thickness meter,triangle defect and secondary ion mass spectrometer to verify the accuracy of 4H-SiC epitaxial layer thickness,in view of the inaccuracy of FTIR measurement,This paper analyzes the FTIR spectrum to determine that it is caused by the uneven doping concentration of the epitaxial wafer.A large number of stacking faults were found in the 480nm luminescence band using a photoluminescence tester.4.Based on the epitaxial wafer grown in this experiment,Prepare 650V and 1200V silicon carbide diode devices respectively,The quality of the epitaxial film was verified.AThrough the development of the device,To study the influence of different silicon carbide epitaxial wafer growth conditions on device performance,The focus is on the influence of the inhomogeneity of epitaxial doping and triangular defects on the performance of SiC JBS.Studies have shown that the uneven doping of the epitaxial layer will cause the dispersion of device performance.The triangular defect will reduce the reverse breakdown voltage of the device and increase the leakage current by 3 orders of magnitude.