SiC MOS器件界面缺陷及其钝化研究

The excellent physical and electronic properties make silicon carbide (SiC) a promising candidate for high temperature, high power, and high frequency electronic devices. However, the metal-oxide-semiconductor field effect transistors (MOSFETs) fabricated on 4H-SiC present extremely low inversion channel mobility due to the high density of interface traps (Dit) at the SiO2/4H-SiC interface. Many studies have been performed to reveal the origin of Dit. And some types of interface defects have been identified, such as carbon clusters, Si/C dangling bonds, and silicon oxycarbides (SiOxCy) species. It has been reported that the nitridation process is very effective in reducing the density of interface traps at the SiO2/SiC interface. In this proposal, we propose a novel passivation technology based on the electron cyclone resonance (ECR) nitrogen plasma. It is expected that the passivation efficiency will be improved and the Dit will be reduced with the reaction between the high-density, high-activity nitrogen plasma and the interface traps. But on the other hand, the mechanism responsible for the improvement of the SiO2/SiC interface quality by nitridation process, which is closely related to the composition and structure of the nitrided interface, still remains unclear. In previous work (APL 99, 082102, 2011), we have studied the structure of the SiO2/4H-SiC (0001) interface without nitridation by ADXPS and proposed a nonabrupt interface structure model. Based on this work, we examine the composition and structure of the nitrided SiO2/SiC interface in present work. The results will show the compositional modifications of the interface traps induced by the nitrogen and the depth distributions of nitrogen and various N-related species. These findings should be provide further insights into the mechanism of nitrogen passivation process at the SiO2/SiC interface and are helpful for exploring more effective passivation processes to improve the performance of SiC MOSFETs towards satisfactory figures. In the proposal, the micro-mechanism responsible for the improvement of SiC MOS interface quality by nitridation and the relationship between the interface traps composition, structure, passivation process, and electronic properties will be investigated thoroughly. These studies will introduct the further fabrication processes of SiC MOS devices.

宽带隙半导体碳化硅（SiC）是一种性能优异的半导体材料，基于碳化硅的功率电子器件研究备受关注。 其中，SiC MOSFET是一类重要的功率控制器件，也是构成未来SiC IGBT器件的重要组成部分。然而，实际制作的SiC MOSFET存在沟道迁移率低的问题，其主要原因是SiO2/SiC界面缺陷密度高。因此，界面缺陷问题成为SiC MOS器件研究的焦点，SiO2/SiC界面组成、结构及其钝化技术至今尚未得到很好解决。 本申请拟在自主开发的电子回旋共振等离子体钝化技术的基础上，通过高密度和高活性的氮、氮氢混合等离子体参与界面钝化过程，提高钝化效率，进而达到降低界面态的目的。同时，利用XPS、SIMS和HRTEM等理化分析技术结合计算材料学方法，研究真实氧化过程中缺陷的形成、结构及其钝化的微观机理，明晰界面缺陷组成、结构、工艺与电学特性间的关系，为改善实际SiC MOS器件工艺提供参考依据。

碳化硅（SiC）半导体是继Si和GaAs之后的第三代半导体材料。它是一种物理化学特性极其优异的宽禁带半导体材料，基于SiC半导体的功率器件可以比硅器件的品质因数优越上千倍。同时，使用这种新型器件的电力系统可以节能降耗高达70%并实现小型化！因此备受关注。由于其在超大功率电力电子系统，如机载舰载设备、超大功率电磁发射装置、航空航天等领域潜在应用的卓越价值，SiC功率器件在超大功率新军事需求背景下，显得极为重要和紧迫。.为解决实际制作SiC MOSFET器件过程中存在的沟道迁移率低的问题，我们针对SiO2/SiC界面缺陷，开发了电子回旋共振等离子体钝化技术，并开辟了通过表面钝化实现界面钝化的新思路。上述工作通过高密度和高活性的氮、氮氢混合等离子体参与界面钝化过程，提高钝化效率，进而达到了降低界面态的目的。同时，利用XPS和SIMS等理化分析技术结合计算材料学方法，研究了真实氧化过程中缺陷的形成、结构及其钝化的微观机理，明晰界面缺陷组成、结构、工艺与电学特性间的关系，为改善实际SiC MOS器件工艺提供了参考依据。.该研究在如下方面取得了重要进展：.1. SiC界面缺陷结构的建立及新型界面缺陷的发现；.2. 新型界面钝化技术的开发；.3. 新型缺陷钝化的物理机制；.4. 在表面缺陷调控、欧姆电极技术、表面清洗等支撑技术上取得了大量新成果。.上述工作，将为开展器件可靠性研究提供强有力的理论和技术支撑。