CMOS Image Sensor for the THESEUS X-ray Space Telescope

瞬态高能天空和早期宇宙勘测者（THESEUS）是由欧洲航天局提出的一项太空望远镜任务，其任务是通过x射线、伽马射线和红外波长的成像来研究早期宇宙。THESEUS将配备一个软x射线成像仪，工作在300 eV到6 keV的能量范围内，计划使用一系列专门的CMOS图像传感器（CIS）作为有源设备。独联体由于具有许多优点，越来越多地用于空间应用。与电荷耦合器件（ccd）不同，CIS在很大程度上不受辐射引起的电荷转移效率低下的影响，并且可以耐受大剂量的电离辐射。此外，CIS消耗更少的功率，并在芯片上集成了数字化和其他功能，大大简化了航天器电子设备并减少了其质量。软x射线成像仪的要求决定了传感器是建立在一个相对较厚的，完全耗尽的硅衬底，并具有大的像素尺寸（例如40微米平方）与非常低的读出噪声和图像滞后相结合。由于需求和现有CMOS技术的局限性之间的相互冲突，这给传感器设计带来了一些挑战。特别是，实现可忽略的图像滞后的解决方案使完全耗尽更加困难，并且可能使感测节点过大，从而增加读出噪声

Proposed by the European Space Agency, the Transient High-Energy Sky and Early Universe Surveyor (THESEUS) is a space telescope mission tasked with studying the early Universe by imaging in the X-ray, gamma-ray and infrared wavelengths. Onboard THESEUS will be a soft X-ray imager working in the 300 eV to 6 keV energy range, which is planned to use an array of specialised CMOS image sensors (CIS) as active devices. CIS are increasingly used in space applications due to their numerous advantages. Unlike Charge Coupled Devices (CCDs), CIS are largely immune to radiation-induced charge transfer inefficiency and can tolerate large doses of ionising radiation. In addition, CIS dissipate less power and integrate digitisation and other functions on-chip, significantly simplifying spacecraft electronics and reducing its mass. The requirements for the soft X-ray imager dictate that the sensor is built on a relatively thick, fully depleted silicon substrate, and has large pixel size (e.g. 40 micrometres square) combined with very low readout noise and image lag. This poses several challenges to the sensor design due to the conflicting interplay between the requirements and the limitations of the available CMOS technologies. In particular, the solutions for achieving negligible image lag make full depletion more difficult, and can make the sense node too large, which increases the readout noise