Advanced Gate Dielectrics for Silicon Carbide Metal Oxide Semiconductor Application

碳化硅是高功率、高频和高温应用中极具吸引力的材料。SiC通过热氧化生长绝缘SiO2层的能力已被用于金属氧化物半导体、MOS、场效应晶体管、场效应管等器件的制造。在SiC/SiO2界面上已经进行了大量的研究，但是到目前为止，i)高密度的界面态和固定的氧化物电荷以及ii)差的可靠性限制了SiC FET器件的功能。此外，已经观察到6H和4H多型之间界面态密度的差异，这些差异尚不清楚，但可能与这两种多型的能带结构之间的差异有关，或者与热生长氧化物中亚氧化物SiOx键合方式的差异有关。由于介电常数的比值，SiO2层中的电场高于半导体中的峰值电场。由于SiC器件在非常高的电场下工作，栅极介电场可能变得非常高，从而导致可靠性问题。本提案将研究当前挑战高性能SiC MOS器件成功开发的几个领域。首先，必须通过电学和分析技术来了解SiO2和SiC的界面性质及其对通道迁移率的影响。6H和4H SiC多型之间的不同行为尚未被理解，需要在原子水平上进行探索。此外，还必须考虑在碳化硅上采用先进的电介质来提高可靠性的问题。SiC器件比Si器件在更高的电场下工作。因此，介电常数比SiO2高的介电介质会产生较小的电场。这就需要对高k介电体如Si3N4、A12O3、Ta2O5、TiO2和ZrSiO4等进行研究。许多这样的电介质已经在积极地研究它们在硅上的潜在应用。本程序通过应用远程等离子体辅助处理和快速热处理来形成sic介电界面来解决上面讨论的界面问题。这包括界面氮化和替代高k介电体的实施。该计划将结合先进的分析方法来表征界面，并就Si器件技术建立电学行为与原子尺度结构和键合之间的重要联系

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.***