Development Of Schottky Junction Device Based On 4H-SiC Single Crystal

The third generation semiconductor materials,also known as wide band gap semiconductors,are widely used in military,medical,lighting and many other fields because of their unique and excellent properties.As the third generation semiconductor material,silicon carbide?SiC?has many excellent and unique properties,such as large band gap,fast electron saturation drift,high critical breakdown field,high temperature and radiation resistance and so on.Because of these excellent properties,SiC is widely used in the manufacturing fields of semiconductor electronic devices such as high power,high temperature,high radiation resistance and so on.At present,most of the SiC Schottky devices are based on epitaxial wafers.In this paper,based on ion implantation technology,Schottky devices are fabricated on single crystal 4H-SiC substrate,and the device structure with thick sensitive region is fabricated.The morphology and electrical characteristics of the device are studied in detail.The different distribution states of N ions in 4H-SiC were compared under different implantation conditions by using SRIM simulation software.The effects of implantation dose,implantation angle and implantation energy on the distribution of N ions are simulated.Finally,it is concluded that when the following parameters are used for ion implantation?tilt angle is 7°;4 times ion implantation;implantation energy is 30 keV,70 keV,120 keV,200keV?,the N ion implantation region with relatively uniform distribution of 400 nm can be obtained.The single crystal 4H-SiC after N ion implantation was annealed at 1450?for 2h to repair the lattice damage and ion electrical activation caused by N ion implantation.Through the UV absorption spectrum,it was found that the absorption intensity of 370⁵00nm increased slightly after ion implantation,and the steep absorption edge was restored after annealing.In the calculation of the peak intensity ratio of E1 and E2 in the Raman scattering spectrum,it is found that the peak intensity ratio increases after ion implantation and returns to the initial value after annealing.It was found by X-ray diffraction spectrum that the corresponding peak position of the?004?crystal plane changes from 35.63°to 35.74°after ion implantation,and a small twin peak appears near the peak position,while after high temperature annealing,the peak position returns to 35.63°and the small twin peak disappears.In the scanning electron microscope image,the surface morphology of the sample annealed at high temperature will be destroyed,while the surface morphology of the sample protected by AlN annealing has been significantly improved compared with the unprotected sample.It is found that hot KOH solution can effectively remove AlN,which is verified by energy spectrum analysis.Through the resistivity test of the ion implantation surface,it is found that the carrier concentration is about 1.0×10¹⁸and the activation rate is about 10%.Al/Ti/Au ohmic electrode and Ni/Au Schottky electrode were prepared by high vacuum evaporation table.The device is simulated by Silvaco software and it is concluded that the turn-on voltage of the device is 8V,the reverse saturation current is 2.5×10^-19A,and the barrier height is1.47eV.After high temperature annealing for 0.5h and 2h,the turn-on voltage of the device is10V and 12V,the reverse saturated leakage current is 1.0x10^-9A and 1.5x10^-8A,and the barrier height is 0.89eV and 0.84eV,respectively.The simulation results of the device deviate from the actual results to a certain extent,because in the process of device fabrication,high temperature annealing can not completely repair the lattice damage caused by ion implantation,which will produce a certain amount of defects in 4H-SiC.High temperature annealing will also reduce the surface morphology of 4H-SiC,and then affect the overall electrical properties.