Study Of Nanometric Cutting Mechanism Of Ion Implanted 6H Silicon Carbide

As a typical third-generation semiconductor material,single crystal 6H-SiC has a very wide application prospect in the semiconductor industry due to its superior physical and electrical properties.However,as a typical hard and brittle material,the brittle removal is very easy to be produced during ultra-precision machining process.On the other hand,the ultra-precision machining method of nanometric cutting of ion implanted material can effectively improve the machining performance and machining effect of hard and brittle materials.Given above information,in order to improve the machinability of single crystal 6H-SiC,the machined surface integrity and the machining precision,the nanometric cutting mechanism of single crystal6H-SiC,the damage formation mechanism of single crystal 6H-SiC induced by ion implantation and the nanometric cutting mechanism of ion implanted 6H-SiC were investigated respectively in this thesis.The main results and conclusions obtained are as follows:?1?Firstly,two characterization technique of Raman spectroscopy and Electron BackScatter Diffraction?EBSD?used in the thesis were analyzed,so as to provide the theoretical basis for subsequent sample characterization and analysis,and ensure the accuracy of characterization results.For Raman spectroscopy technique,the principle and common concept during analyzing characterization results were introduced in detailed.Besides,three significant parameters?penetration depth,spatial resolution and spectral resolution?and corresponding influence factors during Raman characterization were discussed.For EBSD technique,the application and computing method about phase identification and crystal orientation determination were analyzed in detail.?2?Secondly,the ductile removal mechanism of single crystal 6H-SiC was studied.By nanometric cutting experiments of single crystal 6H-SiC,the morphology of machined surface and cutting chip under different cutting depth were observed online,and the results indicated that ductile removal of single crystal 6H-SiC could be achieved when the undeformed chip thickness was smaller than the diamond cutting edge radius and the critical undeformed chip thickness for brittle to ductile transition was close to the size of the cutting edge radius.Also,the results of EBSD revealed that the ductile removal mechanism of single crystal 6H-SiC was closely related to phase transformation to amorphous.?3?Then,the damage formation mechanism of single crystal 6H-SiC induced by ion implantation was studied.Twenty one different ion dose were adopted to implant the single crystal 6H-SiC,and the results revealed that the critical dose threshold and saturated dose threshold for amorphization were around 2.81×10¹⁴ ions/cm² and5.31×10¹⁶ ions/cm²,respectively.The maximum amorphous thickness is obtained when the implantation dose is around 7.13×10¹⁶ ions/cm²,where the surface of material have been removed significantly.A schematic damage model was proposed to explain the damage formation mechanism and indicated that the implantation energy determines the depth range of damage formation,and the implantation dose determines the process of damage formation.?4?Finally,the nanometric cutting mechanism of ion implanted 6H-SiC was studied.By the nanometric cutting experiments of implanted and unimplanted single crystal 6H-SiC,the effectiveness of the method of nanometric cutting of ion implanted material for improving the machinability of single crystal 6H-SiC was proved directly.Besides,on the basis of the cutting chip morphology and theory analysis,a machining model was proposed to explain the material removal process during the nanometric cutting of ion implanted 6H-SiC.