Disruptive Technologies for Electron Bombarded Active Pixel Sensors

各种类型的传感器已在电子轰击模式下运行，包括CCD CMOS传感器和硅传感器（像素化光电二极管）与有源像素传感器（例如Medipix [2]）。该项目旨在为TDCpix [3]开发光子计数能力，TDCpix是一种新开发的具有出色时序分辨率的像素传感器。它是PIPSS和BBSRC与CERN合作开发多通道光子计数探测器的基础，该探测器具有皮秒事件定时，用于生命科学应用。我们最初的IPS项目使用了一个微通道板探测器，并配备了CERN开发的ASIC和时间数字化ASIC。最近由CERN的同一小组开发的TDCpix有源像素传感器提供了可比的时间分辨率（100 ps合并，电子分辨率~ 30 ps），但像素数要高得多（40 x 45 pixel 2，12 x 13.5 mm 2），通过将整个电子设备集成到芯片上，实现了更高水平的小型化，以及每个ASIC ~130 Mcount/s的大幅提高的总体计数率能力，电子轰击的TDCpix将提供无与伦比的性能，并具有商业潜力，可用于时间相关单光子计数（TCSPC）应用如高容量细胞筛选和生命科学领域的其他扩展领域，用于遥感的激光雷达仪器，以及其他各种事件定时应用，其中只有小型阵列的单个光电倍增管是标准的。我们在这个项目中的目标是确定和开发一种使用电子轰击硅器件的光子计数探测器技术，以便将有源像素传感器从真空管中移除，从而大大简化设计、降低制造工艺的风险并提高性能。从管中去除芯片将消除不期望的元素，例如高密度真空电馈电线、具有差真空兼容性的材料以及内部凸块、引线和芯片接合，并且将解除这些对管处理施加的限制，这些限制影响制造产量、器件可靠性以及最终的传感器寿命。鉴于这个项目的成功结果，我们打算提出一个后续的IPS项目，其目标之一是将一个额外的，相对较低（x20）的增益级，使用线性模式电子雪崩过程中的每个像素的硅传感器，匹配的电子轰击操作的要求。这将使电子轰击增益降低，将管工作电压降低到更安全的水平，并减少危及生命的辐射损伤。电子轰击探测器设计的其他元件，包括光电阴极的真空管和硅传感器，将由我们的工业合作伙伴提供; Photek Ltd.，和Micron Semiconductor Ltd。Photek在设计和制造定制真空探测器方面拥有丰富的经验，在电子轰击模式器件方面具有特定的专业知识，已经制造了电子轰击Medipix探测器。美光半导体拥有丰富的经验和传统，为CERN LHC和其他类似实验的恶劣辐射环境生产大量定制像素化硅传感器。特别是对于这个项目，他们开发了一种薄入射窗技术，这是非常理想的电子轰击模式，以尽量减少光电子能量损失。他们目前可用的Type-9.5窗口的厚度为500埃，Type-10窗口正在开发中，厚度目标为200埃。Micron还具有互连开发所需的凸点键合能力。

A variety of sensor types have been operated in electron bombarded mode, including CCDs CMOS sensors, and silicon sensors (pixellated photodiodes) in conjunction with active pixel sensors (e.g. Medipix [2]). This project aims to develop a photon counting capability for the TDCpix [3], a newly developed pixel sensor with exceptional timing resolution. It follows on from a previous PIPSS and BBSRC-funded collaboration with CERN to develop a multi-channel photon-counting detectors with picosecond event timing for life science applications. Our original IPS project utilized a microchannel plate detector with CERN-developed preamplifier and time-to-digital ASICs. The recent development of the TDCpix active pixel sensor by the same group at CERN offers comparable time resolution (100 ps binning, and electronic resolution ~30ps) but with a much higher pixel count (40 x 45 pixel2, 12 x 13.5 mm2), a much higher level of miniaturization provided by integration of the entire electronics on to the chip, and a greatly increased overall count rate capability of ~130 Mcount/s per ASIC, an order of magnitude higher per unit area than its microchannel plate based predecessor.An electron bombarded TDCpix would offer unrivalled performance with commercial potential for applications using time-correlated single photon counting (TCSPC) such as high content cell screening and other expanding fields in the life science sector, LIDAR instruments for remote sensing, and a variety of other event timing applications where only small arrays of individual photomultiplier tubes are the norm.Our aim in this project is to identify and develop a technology for photon counting detectors using electron bombarded silicon devices, in order to remove the active pixel sensor from within the vacuum tube, thus greatly simplifying design, de-risking the manufacturing process, and enhancing performance. Removing the chip from the tube will eliminate undesirable elements such as high density vacuum electrical feedthroughs, materials with poor vacuum compatibility, and internal bump, wire, and chip bonding, and will lift the restrictions imposed by these on tube processing which impact manufacturing yield, device reliability, and ultimately, sensor lifetime. Given a successful outcome to this project, we intend to propose a follow-on IPS project, one of whose goals would be to incorporate an additional, relatively low (x20) gain stage using a linear mode electron avalanche process within each pixel of the silicon sensor, matched to the requirements of electron bombarded operation. This will allow the electron bombardment gain to be lowered, reducing the tube operating voltage to safer levels, and reducing the lifetime-threatening radiation damage.The other elements of an electron bombarded detector design, the vacuum tube including photocathode, and the silicon sensor, will be provided by our industrial collaborators; Photek Ltd., and Micron Semiconductor Ltd, respectively. Photek have extensive experience of design and manufacture of custom vacuum-based detectors with specific expertise in the electron bombarded mode devices, having manufactured an electron bombarded Medipix-based detector. Micron Semiconductor have substantial experience and heritage producing large quantities of custom pixellated silicon sensors for harsh radiation environments at CERN LHC and other similar experiments. Specifically for this project, they have developed a thin entrance window technology which is highly desirable for electron bombarded mode to minimize photoelectron energy loss. The thickness of their currently available Type-9.5 window is 500 Angstroms, and a Type-10 window is under development with a thickness goal of 200 Angstroms. Micron also have a bump-bonding capability necessary for the interconnect development.