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

目前快速扩大的更好的功率半导体市场由硅和氮化镓半导体提供。功率半导体在高电压下开关器件中的电流，从而转换和控制电流。碳化硅（SiC）半导体的使用正引起人们的兴趣，因为它们可以在更高的功率负载和温度下工作，从而减少能量损失并延长设备的寿命。碳化硅功率半导体应用于汽车、消费电子、信息通信、军事航空航天、电力等多个行业。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半导体是通过一种称为MOCVD（金属有机化学气相沉积）的工艺在反应器中生长的。作为该工艺的一部分，SiC晶圆被安装在涂层石墨衬底上。一种常用的涂覆石墨衬底的方法是化学气相沉积（CVD）。涂层形成保护屏障，防止石墨中的杂质影响生长过程。由于碳化钽（TaC）具有高熔点的无孔材料的特性，最近的发展表明碳化钽（TaC）作为石墨涂层具有很大的前景。与目前使用的其他复合涂层相比，这些特性产生了极其可靠和耐用的低成本保护涂层。结果是一个更可靠和高效的生长过程，增加了SiC半导体的产量。世界领先的碳化硅半导体MOCVD反应器制造商爱思强（Aixtron）已与先进炉技术公司（Aftech）接洽，以优化其用于碳化硅半导体生产的MOCVD反应器的TaC涂层石墨部件的工艺。这种成功项目的潜力将提高Aftech和英国在碳化硅半导体应用（如太阳能和风能）以及电动汽车的增长市场中的地位。目前，亚太地区主导着全球市场，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）。爱思强找Aftech来开展这个项目有两个主要原因。首先，爱思强目前的供应商，即韩国和美国的失败。这些问题包括TaC涂层从石墨基板上剥离（脱落），以及由于熔炉尺寸有限和缺乏建造新的合适仪器的能力而无法按比例制造零件。其次，Aftech拥有克服这些挑战的相关经验和专业知识。Aftech相对于竞争对手的主要优势包括有能力建造自己的高温炉和系统，以及在开发CVD系统、沉积碳化钨、氮化铝镓、砷化镓、磷化镓和碳化硅等化学品方面的经验。Aftech在这些方面是独一无二的，这为我们优化TaC涂层石墨的工艺以及制造最终产品提供了相当大的优势。我们认为这是一个重要的机会，可以与佐伊·托尔金博士领导的团队一起推出一种新的有效产品，佐伊·托尔金博士作为我们的研发官，在优化热解石墨涂层工艺和石墨纯度的项目中取得了成功。到目前为止，她在这个职位上表现出了很强的韧劲和潜力，我们有信心通过这个项目让她进一步发挥自己的才能。

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.