Novel GaN Power Devices and Packaging Technologies for 300 degC Ambient Operation

该提案横跨两个关键主题，高温（HT）电子和电力电子。目前的电子产品是硅基的，因此限制了最大工作结温度低于150摄氏度，这使得最大环境温度上限约为105摄氏度。市售元件（额定在高温下工作）的最大温度范围为210-225摄氏度。因此，汽车领域的电子设备，特别是新兴的电动汽车，以及航空航天领域的电子设备都尽可能远离发动机，以最大限度地降低冷却要求。同样，石油和天然气工程师，试图收获化石燃料（我们仍然高度依赖化石燃料），在驱动钻井工具马达的电子设备上面临着完全相同的问题。向电机提供数百瓦功率的电力电子设备必须在超过225摄氏度的环境中运行，在地下10公里或更深的地方运行，只有泥浆从地面泵出以冷却设备（有温度和时间限制）。让电子设备在这些环境中运行而不需要冷却的潜在好处是巨大的，从而提高效率、可靠性、节省空间、重量和重要的成本。电力电子在电力转换中起着非常重要的作用，广泛应用于交通运输、可再生能源和公用事业等领域。到2020年，80%的电力将在发电、传输、分配和消费之间的某个环节通过电力电子转换器。因此，对电力电子变换器来说，高效率、高功率密度和高可靠性是非常重要的。然而，传统的硅基电力电子器件已经达到了其潜力的极限（经过近40年的发展）。基于碳化硅（SiC）和氮化镓（GaN）的器件等宽带隙材料的出现，为实现更紧凑、更高效的功率转换器带来了明显的机会，可以在更高的电压、频率和功率下工作，以及恶劣的环境（例如300℃），因此可以满足一系列现有和新兴应用不断增长的需求。GaN器件结构和工艺技术的进步显著提高了性能，推动了这些新型功率器件在超高压（600 V）、高温（125℃）和大功率（主要是6-40kW）应用中的应用。随着技术的发展，这一趋势将继续下去。对于600V的工作，需要+3V的阈值电压（远高于目前可实现的最大值+1.6V），以提高抗噪性。此外，目前的器件架构会影响转换器的性能，例如，在半桥功率转换器模块中，通过顶部开关晶体管的电流由其浮动衬底电位调制。当这一缺陷得到解决时，所有电力电子系统的基本构建块的两个晶体管可以作为单个集成电路制造，从而减少开关路径电感，从而允许更快的开关和更小更便宜的无源元件，提高小型设备的每片开关成品率并降低封装成本。新器件和集成电路的可靠封装方法对于开发过程中所需的测试以及最终在工业HPHT应用中的开发是必不可少的。在bb0 ~ 300℃环境下所需的材料和连接方法与传统电子产品完全不同，需要开发。高温电子学和氮化镓开关/封装的这些挑战构成了这个项目的主要动机。该项目汇集了英国主要的学术和工业专业知识，协同研究HT封装和GaN功率器件，以实现强大的高性能高功率高温（HPHT）技术。

This proposal straddles two key topics, High Temperature (HT) Electronics and Power Electronics. Present electronics is silicon-based and therefore limited to maximum operating junction temperatures of less than 150 degC, which gives a maximum ambient ceiling of around 105 degC. Commercially available components (rated for operation at elevated temperature) are in the range of 210-225 degC maximum. Therefore electronics for the automotive sector, especially for the emerging electric vehicles, and the aerospace sector is kept as far from the engine as possible to minimise the cooling requirements. Similarly, oil and gas engineers, attempting to harvest the fossil fuels (which we are still highly dependent on), face exactly the same problem with the electronics that are driving the drilling tool motor. Power electronic devices delivering hundreds of Watts of power to the motor must do so in an ambient that can exceed 225 degC, operating 10 km or deeper under the ground with only slurry pumped from the surface to cool the devices (temperature and time restrictions apply). The potential benefit for having electronics operating in these environments without cooling is huge, leading to greater efficiency, reliability, saving space, weight and importantly cost.Power Electronics plays a very important role in the electrical power conversion and is widely used in transportation, renewable energy and utility applications. By 2020, 80% of electrical power will go through power electronics converters somewhere between generation, transmission, distribution and consumption. So high-efficiency, high-power-density and high-reliability are very important for power electronics converters. The conventional Si-based power electronics devices have, however, reached the limit of their potential (after almost 40 years of development). The emergence of wide-bandgap material such as silicon carbide (SiC) and gallium nitride (GaN) based devices has brought in clear opportunities enabling compact, more efficient power converters, operating at higher voltages, frequencies and powers, and harsh environments (e.g. 300 degC ambients) and so can meet the increasing demand by a range of existing and emerging applications. Advances in GaN device structure and in process technology to significantly improve performance are pushing the adoption of these new power devices for very high voltage (>600 V), high temperature (>125 degC) and high power (mainly 6-40kW) applications. This trend is set to continue as the technology evolves. For 600V operation, a threshold voltage +3V would be desirable (well above the +1.6V maximum now achievable) for improved noise immunity. Also, presently, the device architecture compromises converter performance, e.g. in a half-bridge power converter module the current through the top switch transistor is modulated by its floating substrate potential. When this deficiency can be solved, the two transistors of the basic building block of all power electronic systems can be manufactured as a single integrated circuit reducing switching path inductance thus allowing faster switching and smaller cheaper passive components, increasing switch yield per wafer for the small devices targeted and reducing packaging costs.Reliable packaging methods for the new devices and ICs are indispensable for the required testing during development, and for the eventual exploitation in industrial HPHT applications. The required materials and joining methods at >300 degC ambient environments are completely different from those of conventional electronics, and need to be developed. These challenges with HT electronics and GaN switches/packaging form the main motivations for this project.The project brings together the UK's key academic and industrial expertise to work in synergy to investigate HT packaging and GaN power devices to realise a robust and high performance High Power High Temperature (HPHT) technology.