Radiation-hard photodiode structures implemented in medical applications are designed in 180-nm CMOS technology. Designed photodiodes were tested against total ionizing doses (TIDs) of 100, 200, and 400 Gy(Si), respectively, and they show high stability in terms of dark current characteristics. After TID of 400 Gy(Si), the dark current increased by up to 15%, compared to the unirradiated characteristics values. TCAD electrical simulations were performed and calibrated with the dark current measurements in order to explain the impact of generated defects due to ionizing radiation. Parameters that are used to model TID radiation have been varied in physical boundaries in order to achieve the desired fitting with the measurements. It is shown that due to the filling of acceptor interface traps with electrons, the space charge region extends, but the extension is limited and partially compensated by the fixed positive charges in the silicon nitride layer. The presented photodiodes result in the improved radiation hardness over the design in 350-nm CMOS technology.

中文翻译：

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用于医疗应用的 180 纳米 CMOS 技术中光电二极管的辐射硬度评估

在医疗应用中实现的抗辐射光电二极管结构采用 180 纳米 CMOS 技术设计。设计的光电二极管分别针对 100、200 和 400 Gy(Si) 的总电离剂量 (TID) 进行了测试，它们在暗电流特性方面表现出高稳定性。在 400 Gy(Si) 的 TID 后，与未辐照的特性值相比，暗电流增加了 15%。执行 TCAD 电气模拟并使用暗电流测量进行校准，以解释由于电离辐射产生的缺陷的影响。用于模拟 TID 辐射的参数已在物理边界上发生变化，以实现所需的测量拟合。结果表明，由于受主界面陷阱被电子填充，空间电荷区扩展，但扩展受到氮化硅层中固定正电荷的限制和部分补偿。与 350 nm CMOS 技术中的设计相比，所提出的光电二极管可提高辐射硬度。