The Physics and Engineering of Oxide Semiconductors for Large-Area CMOS

在过去的二十年里，电子学和光子学改变了人们的日常生活：硅微处理器在一个可以装在口袋里的设备中提供了巨大的处理能力，液晶显示器使我们能够在手掌上的高分辨率显示器上看到信息，光纤使我们能够长距离高速传输数据。其结果是，我们基本上都是连续连接到互联网，这使我们能够相互沟通，并立即访问信息。其结果是生活的几乎每个方面都发生了深刻的变化，包括工作实践，购物，医疗保健，银行，交通甚至关系。然而，虽然我们是“连接”的，但我们日常生活中的物体世界却不是，下一个大的转变将是将这些物体连接起来。这就是“物联网”的愿景。用英国首相大卫卡梅隆的话来说，“我认为物联网是一个巨大的变革性发展，是一种提高生产力、让我们更健康、提高交通效率、减少能源需求、应对气候变化的方式。”我们正处于新工业革命的边缘。“技术的进步是这种工业革命的驱动力，物联网需要将传感器，RFID，电源，逻辑，显示器，照明和通信集成到我们周围的日常物品中，其形状因素不会对物品的主要功能产生不利影响，无论该物品是我们的汽车，我们的冰箱，我们的衣服，这将需要新一代的电子产品，这种电子产品可以在几乎任何衬底上的大面积上透明地生产，并且是灵活和坚固的。这种基于非晶硅的玻璃基板上的“大面积电子器件”（20世纪70年代诞生于邓迪大学的技术）已经成为平板显示器发展的关键。然而，非晶硅不是光学透明的，并且具有相当差的电子性质（最显著的是低电子迁移率）。非晶离子氧化物由于具有上级的电子性能，近年来已成为显示器应用中非晶硅的替代品。特别地，非晶铟镓锌氧化物（a-IGZO）已经发展到这样的程度，其将很快开始用于商业产品。然而，这种复杂的材料只能制成n型而不能制成p型半导体，因此不能实现互补逻辑，结果是功耗高。此外，它还具有不稳定性，这限制了它的寿命。因此，这种材料不太适合物联网。本项目旨在开发比a-IGZO稳定性更好的更简单的n型非晶离子氧化物半导体，以及互补的p型非晶离子氧化物半导体。这将需要详细了解这些材料的物理特性，特别是杂质的电子作用。我们将对单个材料和由这些材料制成的设备进行广泛的物理测试，包括红外光谱，使我们能够在其应用环境中研究设备。这是至关重要的，因为薄膜器件的性能通常由其表面决定。这将使我们能够开发新的材料和模型的设备，这是至关重要的电路和系统的设计和仿真。如果要应用这项技术，这一点至关重要。我们将通过设计、模拟、制造和测试塑料基板上的四位RFID标签来证明我们的材料、工艺、模型及其应用的有效性。生产这些设备的成本最终应该与印刷相似，允许在英国与其他物体进行在线制造。

Electronics and photonics has transformed everyday life over the last twenty years: the silicon microprocessor provides vast processing power in a device that can fit inside a pocket, the liquid crystal display allows us to see information on a high resolution display that can sit on the palm of our hand, and the optic fibre allows us to transmit data at high speeds over long distances. The result is that we are all essentially continuously connected to the internet, and this allows us to communicate with each other and access information instantly. The result has been a profound change in almost every aspect of life including working practices, shopping, healthcare, banking, transport and even relationships. However, whilst we are 'connected', the world of objects that are so much part of our everyday lives are not, and the next big transformation will be to connect these too. This is the vision of the 'Internet of Things'. In the words of Prime Minister David Cameron, 'I see the Internet of Things as a huge transformative development, a way of boosting productivity, of keeping us healthier, making transport more efficient, reducing energy needs, tackling climate change. We are on the brink of a new industrial revolution.'Advances in technology are the driver for such industrial revolutions, and the Internet of Things needs sensors, rfID, power supplies, logic, displays, lighting and communications to be integrated together onto the everyday objects around us with a form factor that does not adversely affect the prime function of the object, whether that object is our car, our refridgerator, our clothes, our purse or our toothbrush.This will require a new generation of electronics which can be produced transparently over large areas on almost any substrate, and which is flexible and robust. Such 'large-area electronics' on glass substrates based on amorphous silicon (a technology born in Dundee University in the 1970s) has already been critical for the development of flat panel displays. However, amorphous silicon is not optically transparent and has rather poor electronic properties (most nobably a low electron mobility). Amorphous ionic oxides have emeged as a replacement for amorphous silicon for display applications in recent years as it has superior electronic properties. In particular, amorphous indium gallium zinc oxide (a-IGZO) has been developed to such a point that it will shortly start to be used in commercial products. However, this complex material can only be made as a n-type and not a p-type semiconductor, and so complemetary logic cannot be realised with the result that power consumption is high. Also, it suffers from instabilities which limits its lifetime. As a result, this material is less well suited to the Internet of Things.This project aims to develop a more simple n-type amorphous ionic oxide semiconductor with an improved stability over a-IGZO, and a complementary p-type amorphous ionic oxiide semiconductor. This will require detailed understanding of the physics of these materials, and in particular the electronic role of impurities. We will subject both the individual materials and devices made from these materials to a wide range of physical tests, including infrared spectroscopy, allowing us to study the device in its applied environment. This is critical as the performance of a thin film device is often dominated by its surfaces. This will enable us to develop both new materials and models for devices which are critical for the design and simulation of circuits and systems. This is critical if the technology is to be applied. We will demonstrate the validity of our materials, processes, models and their application by designing, simulating, fabircating and testing a four-bit rfID tag on a plastic substrate. The cost of producing these devices should end dup being similar to printing, allowing in-line manufacture with the rest of the object they are enabling in the UK.