The Study Of Ti/Al/4H-SiC MOSFET Ohmic Contacts

Modernization society has higher requirement for applications of semiconductor materials and devices in the field of high-temperature, high-frequency, high power, anti-radiation and so on. Traditional semiconductor materials such as Silicon and Gallium Arsenide see their limits that have not the ability to meet the globalization in those places. Silicon Carbide is the third generation semiconductor material and has quickly gained the attention of researchers in the semiconductor industry due to its superior properties, such as wide band gap, high thermal conductivity, high breakdown voltage, et al. However, full-fledged Si technology can not be completely transferred to SiC in the process of SiC device fabrication and ohmic contact is one of them. Based on investigation on p-and n-type SiC ohmic contact, this paper focuses on the theory, technology and the fabrication of SiC VDMOSFET device. The main results of this research are summarized as follows:1. The band principle forming in p-and n-type SiC ohmic contacts was studied. The commonly test methods, the choice of metal system and the doping technology used for ohmic contacts were also summarized. Ti(20nm)/Al(30nm)/Si(30nm) ternary system was prepared for contact metal system to form p-and n-type 4H-SiC ohmic contact. Transmission line method (TLM) was used to measure the specific contact resistance, and a specific contact resistance of 5.71×10-4Ω.cm2 was obtained. This result has a positive effect on the device performance of SiC MOSFETs. In addition, we used abundant controversial theories analyzing the mechanism of ohmic contact formation, and sentaurus TCAD software simulating the Ti/Al base p-type SiC ohmic contacts.2.Ni based ohmic first technology and SiC VDMOSFET fabrication were studied. Ni based ohmic contact first technology have been developed, and SiC VDMOSFET device was obtained, the first annealing condition was 600℃,2min, ohmic annealing temperature was 1000 ℃ for 2min. Finally, the threshold voltage is about 3.5V and the Reverse Tolerant Voltage(RTV) is 1200V for the SiC VDMOSFET device, mainly realized the characteristic.