Deposition of Tantalum Carbide (TaC) on graphite as a coating barrier during the manufacture of Silicon Carbide (SiC) electronic materials

目前，更好的功率半导体的快速扩张的市场由硅和氮化镓半导体提供。功率半导体在高压下切换设备中的电流，从而转换和控制电力。碳化硅（SiC）半导体的使用越来越受到关注，因为它们在更高的功率负载和温度下工作，减少了能量损失并延长了器件的寿命。碳化硅功率半导体应用于各种行业，包括汽车，消费电子，IT和电信，军事和航空航天以及电力。它们在电动汽车和风力涡轮机等绿色能源应用中越来越受欢迎。SiC半导体通过称为MOCVD（金属有机化学气相沉积）的工艺在反应堆中生长。作为该过程的一部分，将SiC晶片安装到涂层石墨衬底上。涂覆石墨基底的常用方法是化学气相沉积（CVD）。涂层形成保护屏障，以防止来自石墨的杂质影响生长过程。最近的发展已经证明了碳化钽（TaC）作为石墨涂层的巨大前景，这是由于其作为具有非常高熔点的无孔材料的性质。与目前使用的其他复合涂层相比，这些特性以低成本产生极其可靠和耐用的保护涂层。结果是更可靠和有效的生长过程，增加了SiC半导体的产量。世界领先的SiC半导体MOCVD反应器制造商爱思强（Aixtron）已与先进炉技术公司（Aftech）接洽，以优化其SiC半导体生产中MOCVD反应器的TaC涂层石墨部件的工艺。此类项目成功的潜力将提高Aftech和英国在太阳能和风能以及电动汽车等SiC半导体应用增长市场中的地位。目前，亚太地区正在主导全球市场，美国能源部正在投资数百万美元用于各种创新项目（来源：Mordor Intelligence）。Aixtron与Aftech接洽进行该项目有两个主要原因。首先，目前Aixtron供应商的失败，即在韩国和美国。这些问题包括TaC涂层从石墨基底上剥离（不粘），以及由于尺寸有限的熔炉和缺乏建造新的适当仪器的能力而无法按比例制造部件。其次，Aftech拥有克服这些挑战的相关经验和专业知识。Aftech相对于其竞争对手的主要优势包括建造自己的高温炉和系统的能力以及在开发CVD系统、沉积碳化钨、氮化铝镓、砷化镓、磷化镓以及碳化硅等化学品方面的经验。Aftech在这些方面是独一无二的，这为我们提供了相当大的优势，以优化TaC涂层石墨的工艺以及制造最终产品。我们认为这是一个重要的机会，可以与Zoe Tolkien博士领导的团队一起推出新的有效产品，Zoe Tolkien博士一直成功地担任我们的研发人员，负责优化热解石墨涂层工艺和石墨纯度的项目。到目前为止，她在这个角色中表现出了极大的坚韧和承诺，我们有信心通过这个项目促进她进一步发展她的才能。

The rapidly expanding market for better power semiconductors at present is supplied by silicon and gallium nitride semiconductors. Power semiconductors switch electrical current in a device at high voltages, thereby converting and controlling the electricity. The use of silicon carbide (SiC) semiconductors is gaining interest because they work at much higher power loadings and temperatures, reducing energy loss and increasing the life of devices. Silicon carbide power semiconductors are applied in various industries including automotive, consumer electronics, IT and telecommunication, military and aerospace, and power. They are increasing in popularity in green energy applications such as electric cars and wind turbines.SiC semiconductors are grown in reactors by a process called MOCVD (Metal Organic Chemical Vapour Deposition). As part of this process SiC wafers are mounted onto a coated graphite substrate. A common used method to coat the graphite substrate is chemical vapour deposition (CVD). The coating forms a protective barrier to prevent impurities from the graphite affecting the growth process. Recent developments have demonstrated great promise with tantalum carbide (TaC) as a graphite coating due to its properties as a non-porous material with a very high melting point. These properties produce an extremely reliable and durable protective coating at low cost compared with other compound coatings currently in use. The outcome is a more reliable and efficient growth process with increased output of SiC semiconductors. Aixtron, the world-leading manufacturer of MOCVD reactors for SiC semiconductors, has approached Advanced Furnace Technology (Aftech) to optimise the processes of coating graphite parts with TaC for their MOCVD reactors in the production of SiC semiconductors. The potential for a successful project of this kind would increase the position of Aftech and the UK in the growth markets for SiC semiconductor applications such as solar and wind power, and electric vehicles. Currently Asia-Pacific is dominating the global market and the US Department of Energy is investing millions into various innovative projects (source: Mordor Intelligence). Aftech were approached by Aixtron to carry out this project for two main reasons. Firstly, the failures of current Aixtron suppliers, i.e. in South Korea and the USA. These include delamination (unsticking) of the TaC coating from the graphite substrate, as well as the failure to manufacture parts to scale due to restricted sized furnaces and a lack of capacity to build new, appropriate instruments. Secondly, Aftech possess the relevant experience and expertise to overcome these challenges. The major advantages that Aftech holds over its competitors include the capacity to build its own high temperature furnaces and systems and its experience in developing CVD systems, depositing chemicals such as tungsten carbide, aluminium gallium nitride, gallium arsenide, gallium phosphide, as well as silicon carbide. Aftech is unique in these respects and this provides us with a considerable advantage to optimise the processes of TaC coated graphite as well as manufacturing the end product. We see this as a major opportunity to bring in a new and effective product with a team headed by Dr Zoe Tolkien, who has been successfully working as our research and development officer on projects for optimising coating processes with pyrolytic graphite as well as graphite purity. She has shown great tenacity and promise in this role so far and we are confident in promoting her to develop her talents further through this project.