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60Co-γ射线和电子束对CCD辐射效应的比较研究
武大猷
学位类型硕士
导师何承发
2016-05-26
学位授予单位中国科学院大学
学位授予地点北京
学位专业微电子学与固体电子学
关键词电荷耦合器件 60co-γ辐照 电子辐照 辐射损伤 低剂量率损伤增强效应
其他摘要

CCD是一种具有高灵敏度的固态光学成像器件,其被广泛应用于空间侦查和深空探索任务中。由于器件所处的空间环境中散布着大量宇宙射线,它们轰击电子元器件会诱发辐射损伤,严重时引起性能退化、或功能失效甚至器件损毁,这严重威胁着CCD的应用性能和可靠性。同时真实空间环境中辐射的累积是一个剂量率低且漫长的过程,而地面加速辐照实验中通常采用高剂量率辐照,如果器件存在低剂量率损伤增强效应,现存地面模拟实验将高估器件在真实环境中的抗辐射能力,这将给航天任务带来极大的隐患。因此为了准确评估器件在真实环境中的抗辐射能力,有必要针对CCD在不同粒子辐照下的辐射效应和低剂量率环境辐照下的效应进行深入研究。本文针对具有埋沟工艺、复合栅结构且工作在MPP模式下的CCD进行了两种辐照源下的辐射效应研究,获得了CCD在60Co-γ射线和电子束辐照下的辐射损伤特性,其中考察的特征参数包括:电荷转移效率、暗信号、暗信号非均匀性、饱和输出电压和光谱响应,并采用科学的实验手段和合理的数据分析方法,探讨了各参数变化的原因。同时根据实验结果和半导体辐射损伤理论,获得不同粒子辐照下参数退化与辐射损伤的关系,初步确定了位移效应和电离效应对器件参数退化的贡献能力。通过研究得到以下结果:1)暗信号是60Co-γ 辐照下最敏感的参数,本款器件的暗信号存在低剂量率损伤增强效应。辐照和退火数据显示,低剂量率辐照下的暗信号增量是高剂量率辐照加等时退火后的15倍。在随后的高温100℃退火过程中,95%的暗信号可以在48小时内退火,因考MOS结构器件低剂量率增强效应主要受氧化物陷阱电荷和界面陷阱电荷的共同作用,且界面态在100℃不发生明显退火,从而初步认为界面态对暗信号的贡献度不超过5%,低剂量率损伤增强效应主要与氧化物电荷的积累有关。 2)电荷转移效率是均随电子和60Co-γ总剂量的增加而减小,且电子辐照后退化的更明显。对于电子辐照,电荷转移效率在常温退火中有明显波动,但经过高温100℃退火后电荷转移效率变得很稳定,考虑到稳定缺陷大规模退火温度在150℃以上,实验100℃退火不足以使缺陷量明显减少,因此电荷转移效率在这个过程中表现的很稳定。对于60Co-γ辐照,电荷转移效率退化主要受界面态陷阱作用的影响,由于器件工艺对界面陷阱生长有很好的抑制作用,这使的60Co-γ射线辐照下的电荷转移效率不产生明显变化。3)饱和输出电压在不同辐照环境下均随总剂量的增加而降低,且在随后的常温和高温退火中表现稳定。由于饱和输出电压主要受耗尽层深度和输出放大器的影响,而实验中氧化物陷阱电荷在高温下基本退火,因此认为氧化层电荷对耗尽层深度的影响不大,饱和输出电压的变化主要受输出放大器的影响。4)通过60Co-γ射线和电子辐照实验表明,埋沟工艺、复合栅结构及MPP工作模式的CCD可以有效的抑制界面态对在载流子的影响,同时复合栅结构对CCD抗辐射损伤起到一定作用。

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As a solid state optical imaging device with high sensibility, CCD is widely used in space exploration space surveillance and deep space exploration. Due to the substantial cosmic rays scatted in the space radiation environment, they act on the device cause radiation damage which will lead to serious degradation of performance, function failure or even device damage, all these make a serious threat to the application performance and reliability of CCD. At the same time, the accumulation of radiation in real space environment is a low dose rate and long process, but the ground accelerated radiation experiments are usually used in high dose rate irradiation. So if the device would exhibit the enhanced low dose rate sensitivity, the ground experiments will overestimate the device's anti-radiation capability in the real environment, which will minefield of potential hazard to the space mission. Therefore, in order to accurately evaluate the anti-radiation capability of the device in the space environment, it is necessary to study the effects of CCD on the radiation effects of different particles and effects of low dose rates on the ground.In this paper, the radiation effects of CCD in MPP mode are studied in this paper, which is based on the process of buried channel and the structure of the composite gate. The radiation damage characteristics of CCD under 60Co-γ rays and electron beam irradiation were obtained. The characteristic parameters above are concerned: Charge transfer efficiency, dark signal, dark signal non-uniformity, saturation output voltage and spectral response. By means of scientific experiments and reasonable data analysis methods, the reasons for the changes of the parameters are discussed. The contribution ability of displacement effect and ionization effect to the device parameter degradation was preliminarily determined.The following results were obtained through the study: 1)dark signal is the most sensitive parameter of 60Co-gamaγ radiation, and the dark signal of these device posed Enhanced Low-Dosed Rate Sensitivity. Irradiation and annealing data show that the increment of dark signal under low dose rate irradiation is 14 times higher than that of high dose rate. In the subsequent high temperature annealing process at 100℃, 95% of the dark signal can be annealed in 48 hours, due to the annealing of the massive interface traps does not occur at 100℃, So that the contribution of the interface traps to the dark signal is not more than 5%.2) Charge transfer efficiency is one of the most sensitive parameters under electron irradiation. The value decreased obviously after the electron irradiation, fluctuated considerably in the room temperature annealing, and very stable during high temperature annealing. Compared with the electron irradiation, the degradation of charge transfer efficiency under 60Co-γ is mainly affected by the interface traps. Due to the advantage of the device technology, the interface traps is suppressed well, for which the charge transfer efficiency under the 60Co-γ irradiation does not have a significant impact. Annealing temperature of the stable defect is above 150℃, As a result, the annealing can`t reduce the amount of defects significantly, Therefore, the efficiency of charge transfer is very stable.3) Saturation output voltage decreases under different irradiation conditions, and exhibits stable during annealing at room temperature and high temperature. The saturation output voltage is mainly affected by the influences of buried depth of trench and output amplifier. But oxide traps charge will be annealing at high temperatures. Therefore,it is considered that charge in the oxide layer has little effect on depletion layer depth,saturated output voltage change is mainly affected by the effects of the amplifier's output. 4) The irradiation and annealing experiments show that buried trench and MPP working modes of CCD can effectively suppress the influence of interface traps,the irradiated by 60Co-γ degenerated charge transfer efficiency very little. And at the same time,the device of composite gate structure of CCD plays a certain role in anti ionizing damage

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4564
专题材料物理与化学研究室
作者单位中国科学院新疆理化技术研究所
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武大猷. 60Co-γ射线和电子束对CCD辐射效应的比较研究[D]. 北京. 中国科学院大学,2016.
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