Dipartimento di Ingegneria Industriale, Università degli Studi di Trento, 38123 Trento, Italy.
Trento Institute for Fundamental Physics and Applications-Istituto Nazionale di Fisica Nucleare (TIFPA-INFN), 38123 Trento, Italy.
Sensors (Basel). 2023 May 13;23(10):4732. doi: 10.3390/s23104732.
Small-pitch 3D pixel sensors have been developed to equip the innermost layers of the ATLAS and CMS tracker upgrades at the High Luminosity LHC. They feature 50 × 50 and 25 × 100 μm2 geometries and are fabricated on p-type Si-Si Direct Wafer Bonded substrates of 150 μm active thickness with a single-sided process. Due to the short inter-electrode distance, charge trapping effects are strongly mitigated, making these sensors extremely radiation hard. Results from beam test measurements of 3D pixel modules irradiated at large fluences (1016neq/cm2) indeed demonstrated high efficiency at maximum bias voltages of the order of 150 V. However, the downscaled sensor structure also lends itself to high electric fields as the bias voltage is increased, meaning that premature electrical breakdown due to impact ionization is a concern. In this study, TCAD simulations incorporating advanced surface and bulk damage models are used to investigate the leakage current and breakdown behavior of these sensors. Simulations are compared with measured characteristics of 3D diodes irradiated with neutrons at fluences up to 1.5 × 1016neq/cm2. The dependence of the breakdown voltage on geometrical parameters (e.g., the n+ column radius and the gap between the n+ column tip and the highly doped p++ handle wafer) is also discussed for optimization purposes.
小间距 3D 像素传感器已被开发出来，以装备 ATLAS 和 CMS 探测器在高亮度 LHC 的升级的最内层。它们具有 50×50 和 25×100μm2 的几何形状，是在 p 型 Si-Si 直接晶圆键合衬底上制造的，衬底的有源厚度为 150μm，采用单面工艺。由于电极之间的距离很短，电荷俘获效应得到了很大的缓解，这使得这些传感器具有极强的抗辐射能力。在大剂量（1016neq/cm2）辐照的 3D 像素模块的束流测试测量结果确实证明，在高达 150V 的最大偏置电压下具有高效率。然而，由于偏置电压的增加，缩小的传感器结构也会产生高电场，这意味着由于碰撞电离引起的过早电击穿是一个问题。在这项研究中，使用包含先进表面和体损伤模型的 TCAD 模拟来研究这些传感器的漏电和击穿行为。模拟结果与在高达 1.5×1016neq/cm2 的剂量下用中子辐照的 3D 二极管的测量特性进行了比较。还讨论了击穿电压对几何参数（例如，n+ 列半径和 n+ 列尖端与高掺杂 p++ 处理晶片之间的间隙）的依赖性，以优化目的。
