Advanced Gate Dielectrics for Silicon Carbide Metal Oxide Semiconductor Application

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9906255MisraSilicon carbide is an attractive material for high power, high frequency and high temperature applications. The ability of SiC to grow insulating SiO2 layers by thermal oxidation has been used in the fabrication of metal oxide semiconductor, MOS, devices such as field effect transistors, FETs. Significant research has been conducted on the SiC/SiO2 interface, but to date, i) a high density of interface states and fixed oxide charge and ii) poor reliability limit the functionality of SiC FET devices. Additionally, differences have been observed in the interface state densities between the 6H and 4H polytypes that are not understood, but may be related to differences between the band structures of these two polytypes, or alternatively to differences in the way suboxide, SiOx, bonding in the thermally grown oxide lines up with the interface band structure. The electric field in the SiO2 layer is higher than the peak field in the semiconductor by the ratio of dielectric constants. Since SiC devices are operated at very high electric fields, the gate dielectric field can become precariously high resulting in reliability problems.This proposal will investigate several areas that are currently challenging the successful development of high performance SiC MOS devices. First, an atomic level understanding of the interfacial properties of SiO2 and SiC and its effect on the channel mobility must be obtained through electrical and analytical techniques. The disparate behavior between the 6H and 4H SiC polytypes is not understood and needs to be explored at the atomic level. Additionally, the implementation of advanced dielectrics on SiC to improve reliability problems must also be considered. SiC devices are operated at higher fields than Si devices. Therefore, a dielectric with a higher dielectric constant than SiO2 will experience a lower electric field. This warrants the investigation of high-K dielectrics such as Si3N4,A12O3, Ta2O5, TiO2 and ZrSiO4, etc. Many of these dielectrics are already being aggressively studied for their potential implementation on Si.This program address the interfacial issues discussed above by applying remote plasma-assisted processing and rapid thermal processing to the formation of SiC-dielectric interfaces. This includes interfacial nitridation and implementation of alternative high-K dielectrics. The program will combine advanced analytical approaches to interface characterization, and as for Si device technology establish important links betweenelectrical behavior and atomic scale structure and bonding.***