4H-SiC厚外延层少数载流子寿命调控机理与方法研究及其在双极型器件中的应用

Silicon carbide (SiC) is a very promising material for the next generation power devices due to its superior physical and chemical properties. It is expected that SiC power devices with characteristics of high efficiency and low power losses have great potential applications in the future. Most of very high-voltage SiC devices are bipolar devices, and carrier lifetime plays a crucial role in achieving low-loss conduction of the bipolar devices. Therefore, the ability to research and control the carrier lifetime is of vital importance. Based on this, the study of defects and minority carrier lifetime control in 4H-SiC thick epitaxial layers is in urgent need of solution. The goal of the proposal is to explore the physical and chemical properties of the defects in 4H-SiC thick epitaxial layers used for bipolar high-voltage devices. Then, the formation mechanism and the microcosmic structure of the extended defects as well as deep level defects were investigated. Meanwhile, the control technique of the defects was obtained and optimized. Furthermore, the physical connection between the carrier lifetime and defects, and then the evolution of the deep level defects by thermal oxidation in 4H-SiC thick epitaxial layers was investigated. The physical process of carrier lifetime control solution was studied, too. The control method of the carrier lifetime in the 4H-SiC epitaxial layers is put forward. Finally, the control effect and method of carrier lifetime have been verified and optimized through the fabrication of pin diodes, with the aim to satisfy the requirements of 4H-SiC bipolar devices and find application in the development of SiC bipolar devices. The research content of this application is the current international research focus. The successful execution of the proposal will lay a solid foundation for development and application of very high-voltage SiC based bipolar power devices.

宽禁带半导体碳化硅(SiC)具有极好的物理及化学性能，其功率半导体器件具有高效、节能的优点，在未来拥有巨大的应用潜力。SiC超高压器件多为双极型器件，厚外延层中载流子寿命的调控对于实现双极型器件的低损耗至关重要。基于此，4H-SiC厚外延层缺陷和载流子寿命的调控问题急需解决。本项目的研究目标是通过探究双极型高压器件用4H-SiC厚外延层扩展缺陷和深能级缺陷的物理及化学属性，获得缺陷调控规律。然后探明外延层缺陷影响载流子寿命的物理过程以及热氧化过程中深能级缺陷的演化，确定少数载流子寿命调控机制与物理规律，提出调控方案，实现4H-SiC厚外延膜缺陷和少数载流子寿命的调控。最后进行pin二极管的研制，验证和优化少数载流子寿命调控效果和方法，以求在4H-SiC双极型器件的制备中实现应用。本申请是当前国际研究热点，项目的成功实施对SiC基超高压双极型功率器件的发展和将来的应用打下良好的基础。

碳化硅（SiC）作为第三代半导体材料，在高压大功率器件中有巨大的应用潜力。随着SiC材料和器件的发展，外延层中载流子寿命的调控对于实现器件的高性能至关重要。本项目在4H-SiC快速外延生长的基础上，提出立足于SiC厚膜外延生长、外延缺陷和深能级缺陷调控等方面研究目标，开展少数载流子寿命调控机制等实验研究。本项目主要工作集中于在垂直热壁低压化学气相沉积(LPCVD)设备外延生长SiC厚外延层，研究生长技术工艺，建立生长模型，掌握SiC厚膜外延生长技术。通过Nomarski光学显微镜、原子力显微镜、拉曼散射谱、KOH缺陷选择性腐蚀等多种方法对4H-SiC外延形貌缺陷进行研究，建立缺陷模型，研究缺陷形成机制以及消除方法，掌握4H-SiC外延缺陷调控技术。通过高温热氧化/退火和C离子注入工艺降低深能级缺陷的密度，研究厚外延层中扩展缺陷和深能级缺陷的物理化学属性以及分布规律。建立物理模型，研究外延层扩展缺陷以及深能级缺陷对少子寿命的影响机理。通过高温热氧化/退火和高能离子注入等方式进行少子寿命调控，建立热动力学模型，研究热氧化过程中少子寿命调控规律，实现少子寿命的调控。在此基础上进行SiC双极型器件-pin二极管的制备，对其制备条件等进行了探索，并对原型器件进行了电学特性的测试。通过本项目研究，我们在碳化硅厚膜外延生长、外延缺陷形成机制、深能级缺陷以及少子寿命调控研究以及pin二极管制备表征等方面已取得了部分成果，发表十篇学术论文，申请了多项国家发明专利。