FINER: Future thermal Imaging with Nanometre Enhanced Resolution

信息和通信技术（信通技术）不断增加的综合碳足迹是不可持续的，必须开发更高效的设备。热特性分析是设计优化的关键步骤之一，可确保正在开发的新电子设备的效率和可靠运行。然而，精确测量尖端电子设备的温度变得越来越困难或不可能，因为它们的尺寸很小，这就是本提案所面临的挑战。包括GaN在内的宽带隙电子器件在下一代可持续ICT和电力电子领域具有巨大的潜力，有助于减少所需的碳排放。小型化是进一步提高宽带隙电子器件的效率和性能的途径之一，将有源区尺寸减小到<200 nm，类似于硅（Si）电子器件采用的技术途径，使用诸如FinFET的概念。热管理是从器件的有源部分有效提取废热，对于实现高效可靠的纳米级电子器件尤其重要;当它们被“缩放”到纳米尺寸时，热阻增加，这是因为热导率降低和3-D器件结构中的热限制，例如鳍状。虽然对于较低功率密度的Si FinFET，自加热可以相当容易地减轻，但对于在巨大功率密度下操作的“缩放”宽带隙器件，它可能是一个重大的障碍。然而，目前没有具有足够高的空间分辨率的热成像技术（例如，拉曼热成像具有约0.5微米的衍射极限分辨率，>热点尺寸的10倍），以能够精确地测量这些新颖的纳米级宽带隙电子器件的热点温度。相反，我们目前依赖于复杂的热成像模型来估计纳米级器件的温度，具有固有的不确定性-需要测量。需要一个步骤的变化，即亚衍射极限（超分辨率）热成像技术，这是由未来热成像与纳米增强分辨率（FINER）项目解决的。我们将开发一种变革性的基于纳米量子点的热成像（nQTI）技术，首次提供纳米分辨率的热成像。为了展示新开发的技术，我们的应用重点是由我们的国家和国际合作伙伴提供的缩放宽带隙电子器件，但这种技术将被广泛应用。量子点是这种应用的理想选择：它们可以沉积在被测器件表面上，厚度为nm，发射颜色取决于温度，这就是我们用于热成像的原因。结构照明显微镜（SIM）和受激发射耗尽（STED）超分辨率技术最初是为荧光显微镜开发的，但目前不适合热成像，将被利用来实现小至50 nm的分辨率nQTI。nQTI将使纳米尺度的微扰模型得以开发和实验验证。精确的模型将进一步加深我们对纳米级自加热和热扩散的理解，反馈到改进的器件设计和新型热管理解决方案中。这项工作将在设备热成像和可靠性中心（CDTR）进行，该中心因处于高空间和时间分辨率热成像的前沿而享有国际声誉，开创了拉曼热成像。这种专业知识使CDTR成为成功交付该项目的理想选择。工业界对这一计划的慷慨支持表明，这一计划非常有必要，而且他们相信我们有能力成功地实现这一计划。

The ever-increasing combined carbon footprint of information and communications technology (ICT) is unsustainable - more efficient devices must be developed. Thermal characterisation, which feeds into design optimisation, is one of the key steps for ensuring the efficiency and reliable operation of the new electronic devices being developed. However, accurately measuring the temperature of leading-edge electronic devices is becoming increasingly difficult or impossible because of their small size, and that is the challenge addressed in this proposal. Wide bandgap electronic devices including GaN have great proven potential for the next generation of sustainable ICT and power electronics, contributing to the needed carbon emissions reduction. Miniaturization is one of the routes to further increase the efficiency and performance of wide bandgap electronic devices, decreasing the active region size to <200 nm, similar to the technology pathway that silicon (Si) electronics has taken, using concepts such as the FinFET. Thermal management, which is the efficient extraction of waste heat from the active part of the device, is especially important for achieving efficient reliable nanoscale electronic devices; thermal resistance increases as they are "scaled" to nanometre dimensions because of a thermal conductivity reduction and heat confinement in 3-D device structures, e.g. in a fin shape. While self-heating can be mitigated reasonably easily for lower power density Si FinFETs, it is potentially a significant roadblock for "scaled" wide bandgap devices which operate at enormous power densities. However there is currently no thermal imaging technique with a sufficiently high spatial resolution (e.g. Raman thermography has a diffraction limited resolution of about 0.5 micrometer, >10x the hotspot size) to be able to accurately measure the hotspot temperature of these novel nanoscale wide bandgap electronic devices. Instead we currently rely on complex electrothermal models to estimate the temperature of nanoscale devices, with inherent uncertainties - measurement is needed.A step change is required, namely a sub diffraction limit (super resolution) thermal imaging technique, which is addressed by the Future thermal Imaging with Nanometre Enhanced Resolution (FINER) project. We will develop a transformative nano quantum dot based thermal imaging (nQTI) technique to deliver nanometre resolution thermal imaging for the first time. To demonstrate the newly developed technique our application focus is on scaled wide bandgap electronic devices supplied by our national and international partners, however this technique will be widely applicable. Quantum dots are ideal for this application: They can be deposited as a nm-thickness film on the surface of the device being tested, and the emission colour is temperature dependent, which is what we exploit for thermal imaging. Structured Illumination Microscopy (SIM) and Stimulated Emission Depletion (STED) super-resolution techniques which were originally developed for fluorescence microscopy, but are presently unsuitable for thermal imaging, will be exploited to achieve a resolution as small as 50nm for nQTI. nQTI will enable nano-scale electrothermal models to be developed and experimentally verified. Accurate models will further our understanding of nano-scale self-heating and heat diffusion, feeding back into improved device designs and novel thermal management solutions. This work will be done at the Centre for Device Thermography and Reliability (CDTR) which has an international reputation for being at the forefront of high spatial and temporal resolution thermal imaging, pioneering Raman thermography. This expertise makes the CDTR ideally placed to deliver this project successfully. The generous industrial support for this programme demonstrates that there is a great need for this and their belief in our ability to successfully deliver it.