N型和P型兼容的铜基碳化硅欧姆接触机理与关键技术研究

Silicon carbide is an ideal base material for high temperature, high voltage and high stability semiconductor devices. At present, the formation of ohmic contact on both p-type and n-type SiC is one of the bottlenecks in the development of SiC devices. In order to give full play to the advantages of silicon carbide devices, this project proposes to use copper and copper alloy as n-type and p-type compatible silicon carbide ohmic contact metal, study the contact potential barrier between metal and silicon carbide by using the first principle, analyze the carrier transport mechanism of the contact interface, and extract the energy band model. This project will prepare copper/silicon carbide diodes and copper/silicon carbide MIS capacitors, propose a more accurate leakage test method to evaluate the stability and interface characteristics of the ohmic contact system, and clarify the degradation mechanism of silicon carbide ohm at high temperature. In this project, experimental design and response surface modeling are used to optimize the structure of copper-based metallization, surface treatment and annealing process. In this project, n-type silicon carbide ohmic contact with specific contact resistance of 10-6Ω∙cm2 and p-type silicon carbide ohmic contact with specific contact resistance of 10-5Ω∙cm2 will be obtained. The specific contact resistance of the contact system will be controlled within 15% after aging at 500℃for 100 hours. This will provide theoretical basis and technical support for obtaining higher quality Ohmic contact of silicon carbide devices.

碳化硅是高温、高压、高稳定性半导体器件的理想基础材料。目前，同时在p型和n型SiC上形成欧姆接触是碳化硅器件发展的瓶颈问题之一。为了更好地发挥碳化硅器件的优势，本项目提出铜及铜合金作为N型和P型兼容的碳化硅欧姆接触金属，利用第一性原理研究金属与碳化硅的接触势垒，分析接触界面的载流子输运机制，提取能带模型。制备铜基/碳化硅二极管和铜基/碳化硅MIS电容，提出更为精确的漏电测试方法进行欧姆接触体系稳定性及界面特性的评估，明晰碳化硅欧姆接触高温退化机理。利用实验设计与响应表面建模方法实现铜基金属化体系结构、表面处理及退火工艺的优化设计，获得比接触电阻可达到10-6Ω∙cm2量级的n型碳化硅欧姆接触和比接触电阻达10-5Ω∙cm2量级的p型碳化硅欧姆接触，接触体系在500℃大气环境下老化100小时后，比接触电阻变化控制在15%内。本项目将为获得质量更高的碳化硅器件欧姆接触提供理论依据和技术支撑。

碳化硅是高温、高压、高稳定性半导体器件的理想基础材料。和相对成熟的n型SiC欧姆接触相比，获得高质量的p型SiC欧姆接触依旧是个挑战。为了更好地发挥SiC半导体器件的优势，p型SiC的比接触电阻值应当和n型SiC获得的比接触电阻值相匹配。本项目提出Cu基欧姆接触体系作为N型和P型兼容的碳化硅欧姆接触金属，深入研究金属与碳化硅的接触势垒，分析接触界面的载流子输运机制，明晰形成欧姆接触的能带原理以及金属/SiC材料欧姆接触形成的机理。成功制备了Cu/Ti/Al和Cu/Ti/Al/Ni欧姆接触体系，采用精确的测试方法对欧姆接触体系稳定性及界面特性进行精准评估。通过高温稳定性研究，深入研究势垒高度和欧姆接触界面特性，明晰SiC欧姆接触的高温失效机制。同时对金属结构参数和退火条件进行优化设计，针对不同比例的Cu/Ti/Al欧姆接触电学特性，当Ti:Al=1:6时，Cu/Ti/Al接触在800℃退火下就能形成欧姆接触，实现最小比接触电阻为2.0×10-5Ω·cm2。当Ti:Al=1:4时，Cu/Ti/Al接触的比接触电阻值不随退火温度有太大的改变，老化实验后，比接触电阻变化率在15%之内。Cu的加入能够降低传统Ti/Al接触体系形成欧姆接触的SiC掺杂浓度和退火温度，工艺成本和制备难度都能降低。相对比Cu/Ti/Al接触，Cu/Ti/Al/Ni体系中的金属Ni作为保护层能有效提高欧姆接触的热稳定性，并限制接触表面的氧化。本项目通过理论分析、铜基欧姆接触体系设计、优化工艺方法，形成了完备的SiC 欧姆接触方案，制备出兼具低比接触电阻和高热稳定性的欧姆接触，为获得质量更高的碳化硅器件欧姆接触提供理论依据和技术支撑。