Key Technology Research And Device Fabrication Of 4H-SiC MOSFET

Silicon carbide(SiC) metal-oxide-semiconductor field-effect transistors(MOSFETs) have very broad application prospects in the field of power electronics due to their lower specific on-resistances, higher blocking capabilities and faster switching speed. By present, SiC has formed a more mature industry overseas and SiC MOSFET has been promoted comprehensively in Electric Vehicle/Hybrid Electric Vehicle, Rail, Solar Power, Motor control etc. However, SiC MOSFET is still in the development stage at home. Based on domestic conditions for scientific research, we developed single-step processes and the fabrication of SiC MOSFET in this paper.Firstly, The simulation of ion implantation was conducted by using Silvaco Athena and Srim Trim and the result was compared and validated with the experiment. Secondly, The compatibility of SiC ohmic contact based on Ni/Ti/Al and the self-aligned silicide process was verified. The results indicated that the Al melted in the annealing process would damaged the alloy surface of the device. Therefore, P/N type SiC ohmic contact with Ni was developed based on self-aligned silicide process. Then, the paper focused on the control technology of SiC MOS. The methods and layouts were designed for extracting interface states of the SiC MOS capacitors and the channel mobility of the SiC surface. The oxidation process and NO annealing process was characterized and the channel mobility of the LDMOSFET operated with NO annealing after oxidation process was 17cm2/V·s.The 1200 V SiC MOSFETs and complete tests were carried out by the integration of the development. The threshold voltage of the device was 2.9V and working current could be up to 12 A. The reverse leakage was 200 nA at a VDS of 1200 V and the gate leakage current was 20 nA at a VGS of 45 V. Two groups of components were conducted under the condition of VGS of 20 V and VDS of 960 V in the environment of 175 oC. After 168 hours test, the shift of the threshold voltage, the breakdown voltage and the conduction resistance pressure was less than 20%. As a consequence, the basic performance requirements was achieved for SiC industry of MOSFET device.