arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1111.1180physics.ins-det
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硅传感器的X射线辐射损伤研究

Study of X-ray Radiation Damage in Silicon Sensors

Jiaguo Zhang, Eckhart Fretwurst, Robert Klanner, Hanno Perrey, Ioana Pintilie, Thomas Poehlsen, Joern Schwandt

摘要:

欧洲X射线自由电子激光器(XFEL)每秒将提供30,000个完全相干的高亮度X射线脉冲,每个脉冲的持续时间低于100 fs。这将允许记录单个复杂分子的衍射图案和研究超快过程。硅像素传感器将用于记录衍射图像。在3年的操作中,传感器将暴露于高达1 GGy的12 keV X射线剂量。在该X射线能量下,预期硅中没有体损伤。然而,在覆盖硅的绝缘层中的固定氧化物电荷和在Si-SiO2界面处的界面陷阱将通过照射引入并随着时间积累。我们已经调查了测试结构中的微观缺陷和作为X射线剂量的函数的分段探测器的宏观电学性质。从测试结构,我们确定的氧化物电荷密度和界面陷阱的密度作为剂量的函数。我们发现,这两个饱和(甚至减少)的剂量之间的10和100毫戈瑞。对于分段传感器,由X射线引入的缺陷增加了全耗尽电压、表面漏电流和像素间电容。我们观察到在Si-SiO2界面处形成了电子积累层。其宽度随剂量增加而增加,随偏置电压减小而减小。使用TCAD模拟与剂量相关的参数从测试结构,我们能够重现所观察到的结果。这使我们能够针对XFEL要求优化传感器设计。

英文摘要:

The European X-ray Free Electron Laser (XFEL) will deliver 30,000 fully coherent, high brilliance X-ray pulses per second each with a duration below 100 fs. This will allow the recording of diffraction patterns of single complex molecules and the study of ultra-fast processes. Silicon pixel sensors will be used to record the diffraction images. In 3 years of operation the sensors will be exposed to doses of up to 1 GGy of 12 keV X-rays. At this X-ray energy no bulk damage in silicon is expected. However fixed oxide charges in the insulating layer covering the silicon and interface traps at the Si-SiO2 interface will be introduced by the irradiation and build up over time. We have investigated the microscopic defects in test structures and the macroscopic electrical properties of segmented detectors as a function of the X-ray dose. From the test structures we determine the oxide charge density and the densities of interface traps as a function of dose. We find that both saturate (and even decrease) for doses between 10 and 100 MGy. For segmented sensors the defects introduced by the X-rays increase the full depletion voltage, the surface leakage current and the inter-pixel capacitance. We observe that an electron accumulation layer forms at the Si-SiO2 interface. Its width increases with dose and decreases with applied bias voltage. Using TCAD simulations with the dose dependent parameters obtained from the test structures, we are able to reproduce the observed results. This allows us to optimize the sensor design for the XFEL requirements.

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