p+深层扩散结构提高p-in-n硅微条探测器抗辐照性能的机理研究

Silicon micro-strip detectors are employed for vertex detectors and track detectors by the international physical laboratories because of its high resolution both in energy and space, wide linearity range, fast response and small volume. They are also largely used in the external target facility in HIRFL-CSR in IMPCAS. The Microelectronics Technology Lab in IMPCAS has developed p-in-n silicon micro-strip detectors, but they are very sensitive to structural damage. Because of their poor resistance to radiation, we expect to develop deep p+ diffusion structure micro-strip detectors using deep p+ diffusion technology to form gradient of the effective space charge distributing near the p-n junction in the detectors, which could make the charge multiplication take place in the irradiated detectors in low bias voltage. Therefor the signal amplitude and also the radiation hardness would be improved. The performance between structural and technical parameters and radiation properties would be obtained by the process simulations and irradiation experiments, which could provide the efficient data support for improving the detection performance of this kind. Our study could provide p-in-n silicon micro-strip detectors for Lanzhou Spectrometer with better radiation hardness and longer lifetime.

硅微条探测器具有能量、位置分辨高，体积轻巧等优点，国际上各高能物理实验室的大型实验谱仪相继采用了硅微条探测器作为顶点探测器和径迹探测器。中国科学院近代物理研究所的HIRFL-CSR外靶终端实验谱仪也需要大量使用硅微条探测器。近物所微电子工艺实验室成功研制了p-in-n硅微条探测器，但该类探测器对辐照损伤很敏感。本项目针对目前现有探测器抗辐照性能差的特点，在不改变原有硅衬底的基础上，拟采用p+ 杂质深层扩散在探测器pn结附近产生具有梯度分布的有效空间电荷的方法，研制P+深层扩散结构硅微条探测器，使其在辐照损伤后，在较低的反向偏压下，能实现电荷倍增效应，提高探测器信号幅度，增强探测器的抗辐照性能。我们通过工艺模拟和辐照损伤实验，获得结构及工艺参数与抗辐照性能之间的变化规律，从而为进一步提高该类探测器性能提供数据支持。该研究可为兰州实验谱仪提供一种抗辐照性能好、寿命长的p-in-n硅微条探测器。

国内外各高能物理实验大型谱仪，都需要使用大量的硅微条探测器。核物理实验谱仪要求硅微条探测器能够应对高强度、高通量的辐照，能够长期稳定工作。然而常规硅微条探测器的缺点是对辐照损伤比较敏感。随着入射粒子辐射通量的增加，探测器灵敏度下降，性能变差。本项目通过模拟、计算、制备及测试，研究了一种新型的p+ 深层扩散结构p-in-n硅微条探测器的电学性能和探测性能。基于pn结电荷雪崩倍增的理论和方法，研究了该类型探测器实现电荷倍增，从而增大其辐照损伤后的灵敏度和信号幅度的机理。主要成果包括：首先，研制了灵敏面积为10mm×10mm的单面硅微条探测器，p+ 注入条条宽64μm，p+ 深层扩散区宽度10µm，栅宽96μm。该结构探测器在45V全耗尽偏压下，各条的反向漏电流均小于1.3nA，对241Am α粒子的能量分辨约为2.6%，相邻条之间的相互影响(crosstalk)为4%。其次，通过计算确定了p+ 深层扩散结构发生雪崩倍增的关键参数，给出了在较低偏压下实现电荷倍增所需探测器结构、工艺和外加偏压条件。深入研究p+ 深层扩散结构p-in-n硅微条探测器的抗辐照机理，对提高辐照损伤探测器的灵敏度，延长探测器使用寿命具有重要研究价值。同时，能为更薄衬底和p型衬底硅微条探测器抗辐照研究提供新的思路和理论依据。