基于GEANT4模拟分析不同能量质子在CMOS APS中的位移损伤研究

Simulation of Proton-induced Displacement Damage Effect in CMOS APS Based on GEANT4

本文针对图像传感器在空间辐射环境中电学性能退化问题,采用蒙特卡罗方法基于互补金属氧化物半导体(CMOS)APS器件建立几何模型,开展不同能量质子与靶原子的相互作用过程研究。通过研究不同能量质子辐照下初级碰撞原子的能谱分布及平均位移损伤能量沉积随质子能量的变化,讨论不同能量质子及空间站轨道质子能谱下在CMOS APS器件中位移损伤的差异。计算结果表明:随着入射质子能量的增大,辐照产生的初级碰撞原子的最大能量及核反应产生的初级碰撞原子(PKA)对位移损伤能量沉积的贡献逐步增加;对于大于1 MeV的质子辐照,CMOS APS器件中位移损伤研究可忽略氧化层的影响;不同能量的质子和CREME96程序中空间站轨道质子能谱下器件中位移损伤能量沉积分布结果显示,3.5 MeV质子与该空间站轨道质子能谱在器件敏感区中产生的总位移损伤能量沉积相近。该工作对模拟空间站轨道质子辐照下电子器件暗电流增长研究中辐照实验的能量选择,提供了参考依据。

Complementary metal oxide semiconductor(CMOS)image sensors have great application potential in space environments because of its small size,low power consumption,high integration and other advantages.In the space radiation environment,the electrical performance of devices will degrade due to the displacement damage effect caused by energetic particles,which in turn affects the reliability and stability of the spacecraft.Aiming at the problem of image sensor’s electrical property degradation in space radiation environment,Monte Carlo method was adopted to establish a geometric model based on CMOS APS device in this paper.Then the research on the interaction process between different energy protons and target atoms was conducted,and the type and number of primary knock-on atom(PKA)generated by different energy protons in the depletion zone were calculated by binary collision approximation method.By comparing the PKA energy spectra and the mean displacement damage energy at different depths for various energy of incident protons,the discrepancy of displacement damage under various energy incident protons and space station orbit proton energy spectrum was analyzed.The result shows that the PKA energy spectrum is basically the same when the incident proton energy is greater than 30 MeV.The difference is that as the incident proton energy increases,the maximum energy of PKA and the contribution to the displacement damage energy from PKA produced by nuclear reaction gradually increase.For proton with energy greater than 1 MeV,the oxide layer in CMOS APS device has so little effect on displacement damage that it can be ignored.The result of the displacement damage energy deposition distribution in the device under different energy of incident proton and space station orbit proton energy spectrum by CREME96 model shows that,the total displacement damage energy in depletion region calculated from the space station orbit proton energy spectrum is approximately equal to the total displacement damage energy produced by the single energy 3.5 MeV proton incidence.This study provides a theoretical simulation reference for the selection of the proton energy in the experimental study of the dark current growth of electronic device in the space station orbit proton energy spectrum,and the energy spectrum distribution provides input parameters for molecular dynamics simulation calculations,which can further simulate the defect caused by cascade collision at the atomic level.