The Study Of Electrical Properties On Trench Structure 4H-SiC Schottky Barrier Diodes

SiC is superior than others in the band gap,the carrier drift velocity saturation,the breakdown electic field strength,conductivity and so on.Therefore,SiC has a very broad prospects and attracts widespread attention.SBD is semiconductor rectifying junction,and minority carrier storage effect can be ignored.So it has good frequency characteristics, low on-state resistance, low power consumption, and no diffusion capacitance, switching speed, these characteristics determine the SBD used in high frequency, high power devices.Currently the a high level of various types of SiC devices have been developed successfully, but it is still in the research phase. SiC devices on domestic research started late, a large gap with foreign countries. Still many problems in the high-voltage SiC SBD studies, such as optimize the design of the junction termination structure, the growth of the oxide layer, ohmic contacts, schottky contacts and other process problems.From the realistic significance SiC SBD, it discusses the properties of SiC semiconductor material, combined with the metal-semiconductor contact theory, based on Ni-based SiC SBD-related process has been investigated, and focuses on the conditions on the reverse breakdown device Effect of voltage and forward IV characteristics.The Optimal parameters are d=15?m,Nd=6?1015cm-3,t=1.8?m,LFP=20 ?m.The main contents of this paper are summarized as follows:1.Sivaco-TCAD is used for 4H-SiC SBD simulation studies, the results include: process structure, a positive characteristic, the reverse breakdown characteristics, according to the parameters obtained in the literature related to the conditions set, the preparation of the simulation program, the introduction of p + ring effectively improve the reverse breakdown characteristics2.The junction termination structure influence on breakdown voltage of the device. Firstly the SBD field plate structure, the results indicate that the oxide layer thickness of 0.4?m, when the field plate structure is longer than 8?m, the maximum breakdown voltage of the device; Secondly, the field plate structure with field limiting ring SiC SBD, optimize the field limiting ring doping concentration and length of the field plate, and found that, different doping concentrations, SiC SBD maximum field plate breakdown voltage of different lengths; Finally, as a semi-insulating polycrystalline silicon Schottky diode with a dielectric layer to give the device structure of the reverse breakdown voltage of 2190 V, 94.1% of the theoretical value.3.Ohmic contact on surface treatment, reactive ion etching(RIE) 4H-SiC SBD, the preparation of 4H-SiC SBD semi-insulating polysilicon dielectric layer structure are studied. First the influence of surface treatment and annealing of the ohmic contacts is researched, the results show that after SiC epitaxial wafers dry oxidation and BOE etching process, it can be formed a good ohmic properties in the surface. Then the impact of reactive ion etching of 4H-SiC SBD characteristics was experimented, it shows that the maximum etch rate of etching with minimal damage case is 480 nm/min. Finally, the semi-insulating polysilicon dielectric layer structure of 4H-SiC SBD, the experiments show, 4H-SiC Schottky diode breakdown voltage SIPOS field plate structure reaches accounted for 60% 1400 ~ 1500 V, the experimental value reached 1630 V, is 74.5% of the theoretical value, and the Schottky diode structure SiO2 field plate breakdown voltage of the experimental value of the average in 1150 V.