Fast timing silicon pixel detectors for new applications

硅传感器在许多领域都是必不可少的，从前沿研究（例如粒子物理，化学，材料科学）到工业（农业，制造业）和日常设备（相机，安全）。它们是我们电子世界的眼睛。随着我们开发出更精确的传感器，例如像素更小的相机，这些设备的潜在覆盖范围也会增加，从而可以研究更多的过程，并提供更多的细节。目前这种传感器的分辨率在微米级。然而，由于在为硅中的信号分配时间方面存在重大的技术挑战，时间精度相对要差得多。小像素硅传感器的最佳精度是纳秒级（ns）。相比之下，光每秒传播30万微米。由于时间精度的限制，我们观察许多过程的能力受到很大的阻碍。对于快速（持续时间约1ns）的过程，将皮秒级（1ps = 0.001ns）的时间添加到微米级的空间测量中，可以有效地对应静止图像和视频之间的差异，因此有可能开辟全新的研究领域。例如，在粒子和核物理学、化学和材料科学中就会发生这样的过程。该项目的最终目标是开发传感器，首次同时在空间上达到微米级精度，在时间上达到皮秒级精度：用于最小可观测尺度的高速摄像机。我们从过去十年才发展起来的一种新型传感器开始：低增益雪崩探测器（LGAD）。通过在硅上添加特殊处理的半导体层，信号采集时间显著缩短，使其精度达到~30ps。然而，迄今为止开发的唯一设备是大（毫米大小）的pad，而不是像素。我们的研究计划将集中在如何将这些设备转化为像素传感器，通过考虑新的几何形状和掺杂方法，以及薄传感器。关键是在像素内保持尽可能均匀的电场，以确保快速的信号发展。我们已经开始了初步研究，包括原型设备的制造，现在我们准备进入积极的研发阶段。来自格拉斯哥大学和曼彻斯特大学的研究人员将与一家商业半导体制造商（美光）合作，设计和制造一系列新的LGAD传感器，并使用几种高科技方法（“瞬态电流技术”- TCT和“双光子吸收”- TPA）分析它们的性能。同时，我们将使用TCAD模型开发探测器的真实模拟，以预测不同设计下的传感器特性。这些模拟将使用我们测量的TCT和TPA结果进行验证。我们所有的研究结果都将发表在开放获取的期刊上，使我们离“4D”精密传感器的梦想又近了一步。同时，我们将开发这些新设备的潜在受益者网络，特别是在材料科学和质子治疗领域。我们已经同这些领域的代表建立了联系，他们将从两个专门的讲习班开始，帮助我们建立网络。这些将用于构建定义所需技术性能的规范文档。他们还将使我们能够进一步在英国和其他地区发现这项新技术的更多潜在用户。

Silicon sensors are essential in a range of fields, from cutting-edge research (e.g. particle physics, chemistry, materials science) to industry (agriculture, manufacturing), and everyday devices (cameras, security). They are the eyes of our electronic world. As we develop more precise sensors, for example cameras with smaller pixels, the potential reach of these devices increases, allowing more processes to be investigated, and with more detail.Currently the resolution of such sensors is at the micrometre level. However, the time precision is relatively much worse, due to significant technological challenges in assigning times to the signals in the silicon. The best precision for small-pixel silicon sensors is at the nanosecond (ns) level. By comparison, light travels 300,000 micrometre per ns. Our ability to observe many processes is significantly hampered by limitations in time precision.For fast (~1ns duration) processes, adding picosecond-level (1ps = 0.001ns) timing to micrometre-level spatial measurements effectively corresponds to the difference between still images and video, and hence has the potential to open up entire new fields of research. Such processes occur, for example, in particle and nuclear physics, chemistry, and materials science. The ultimate aim of this project is to develop sensors that for the first time simultaneously reach precision at the micrometre-level in space, and picosecond-level in time: a high-speed video camera for the smallest observable scales.We start from a new type of sensor only developed in the past decade: Low Gain Avalanche Detectors (LGAD). By adding specially-treated semiconductor layers to the silicon, the time of signal collection is significantly reduced, making it possible to reach ~30ps precision. However, the only devices so far developed have large (mm-size) pads rather than pixels. Our programme of research will focus on ways to transform these devices into pixel sensors, by considering new geometries and doping approaches, and thin sensors. The key is to maintain as uniform an electric field as possible within the pixel, to ensure fast signal development. We have started preliminary studies, including fabrication of prototype devices, and now we are ready to push forward with an aggressive research and development phase.Researchers from the Universities of Glasgow and Manchester will work with a commercial semiconductor manufacturer (Micron) to design and fabricate a range of new LGAD sensors, and analyse their performance using several high-tech methods ('transient current technique' - TCT and 'two photon absorption' - TPA). In parallel, we will develop realistic simulations of the detectors using TCAD models, to predict the sensor characteristics under different designs. These simulations will be validated using the TCT and TPA results from our measurements. All of our results will be published in open-access journals, taking us a step closer to the dream of '4D' precision sensors.In parallel, we will develop a network of potential beneficiaries of these new devices, in particular for the fields of materials science and proton therapy. We have already established connections with representatives within these areas, who will help us to build the network, starting with two dedicated workshops. These will be used to build a specifications document where the required technology performances are defined. They will also enable us to reach further to identify more potential users of this new technology, in the UK and beyond.