New Structure Design And Experimental Investigation Of High Voltage SiC PiN Power Diode

Silicon Carbide?SiC?material has prominent advantages over Silicon?Si?material such as high electron saturation drift velocity,high thermal conductivity,high critical breakdown electric field strength and outstanding irradiation resistance.The high voltage SiC bipolar device can obtain a lower conduction voltage drop and a higher on-state current while having a high breakdown voltage due to the effect of the conductivity modulation,which is especially suitable for high power,high temperature and anti-irradiation application environment,becoming the focus in recent research of power semiconductors.As a bipolar power diode,4H-SiC PiN diode is an important power diode applied in the field of high-voltage and high-power rectification field,which has broad application prospects and profound development potential.At present,domestic research on SiC materials and 4H-SiC PiN power diodes is just in the preliminary stage,and there is still a large gap in technical level compared with foreign leading teams.In this thesis,the current-enhanced new structure for 4H-SiC PiN diodes has been designed and optimized,the layout drawing and tape-out experiment of the new structure diode were carried out based on the domestic silicon carbide process conditions,so as to offer a reference for related investigation on 4H-SiC PiN device in domestic.Based on the Silvaco TCAD semiconductor simulation software,the dissertation first designed the basic cell of the 3300V 4H-SiC PiN diode that the thickness of the drift region was determined to be 30?m and the doping concentration was 3×10¹⁵cm^-3.The simulation results show that the breakdown voltage of the cell is 4850V and the turn-on voltage at a forward current density of 100A/cm² is 3.3V.In addition,the influence of temperature and carrier lifetime on the forward conduction characteristics of 4H-SiC PiN diodes has been investigated in this dissertation,and the effect mechanism of deep-level defects in 4H-SiC epitaxial materials on carrier lifetime was further explored.Next,the current-enhanced new structure of 4H-SiC PiN diode with p type buried layer and trench anode region is proposed in the dissertation.The current enhancement mechanism of the two new structures was analyzed in detail,the basic electrical characteristics of the new structure diodes have been simulated and optimized.After that,the ion implanted 4H-SiC PiN diode with trench anode region was determined as the diode structure in the tape-out experiment,and the junction termination of the diode has been investigated and designed.The conventional field-limited ring termination structure was designed and optimized and a new two-zone etched JTE structure with p⁺implantation ring was proposed of which the terminal efficiency reached 96%.Finally,the dissertation draws out the layout and design the process flow of the ion implanted 4H-SiC PiN diode with trench anode region.The key processes in the tape-out experiment were briefly described and investigated,the ion implantation doping distribution of trench type P⁺anode region was simulated and the experimental design of p-type ohmic contacts with different process parameters is performed in order to obtain better specific contact resistance.