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Interface Passivation for Silicon Dioxide Layers on Silicon Carbide

Sarit Dhar, Shurui Wang, John R. Williams, Sokrates T. Pantelides, and Leonard C. Feldman Abstract Silicon carbide is a promising semiconductor for advanced power devices that can outperform Si devices in extreme environments (high power, high temperature, and high frequency). In this article, we discuss recent progress in the development of passivation techniques for the SiO2/4H-SiC interface critical to the development of SiC metal oxide semiconductor field-effect transistor (MOSFET) technology. Significant reductions in the interface trap density have been achieved, with corresponding increases in the effective carrier (electron) mobility for inversion-mode 4H-SiC MOSFETs. Advances in interface passivation have revived interest in SiC MOSFETs for a potentially lucrative commercial market for devices that operate at 5 kV and below. Keywords: channel mobility, interface passivation, interface states, metal oxide semiconductor field-effect transistors, MOSFETs, silicon carbide, silicon dioxide.

Introduction Scientists and engineers realize that the development of cost-effective semiconductor devices for high-temperature/highpower environments will support major advances in power electronics and sensing technology. Applications are numerous, including electric power conditioning, transmission, and distribution; industrial motor control; electric vehicles, aircraft, and ships; radiation-hardened instrumentation; and downhole well logging in the petroleum drilling industry. The replacement of Sibased systems for these applications will likely result from the successful development of wide-bandgap semiconductor materials like SiC, the Group III nitrides (GaN, AlN, and BN), and diamond. Successful development of the widebandgap family of semiconductors will have a substantial and positive economic impact. Significant cost reductions per aircraft/ spacecraft can be achieved as the result of reduced size and weight, higher efficiency for power/fuel usage, simpler systems design, and improved long-term reliability.

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On-engine sensing devices and circuits for the automotive industry will lead to higher fuel efficiency and significantly less pollution. For electric power generation and distribution, a report by the National Research Council estimated that a 5% improvement in operating efficiency— based on the use of SiC power switching electronics—could eliminate the need for approximately $50 billion in new power plant and transmission line construction over a period of 25 years.1 Selection of the wide-bandgap materials that provide these important societal advances will depend not only on the intrinsic properties of the material, but also on the cost and ease of reliable device manufacturing. An important lesson gleaned from Si is that ease of materials processing is a key to a successful technology. It is well known that Si has been favored over Ge primarily because of the higher-quality native oxide possessed by Si. Several widebandgap semiconduct