非聚焦电子束照射SiO2薄膜带电效应

采用考虑电子散射、俘获、输运和自洽场的三维数值模型, 模拟了低能非聚焦电子束照射接地SiO₂薄膜的带电效应. 结果表明, 由于电子的迁移和扩散, 电子会渡越散射区域产生负空间电荷分布. 空间电荷呈现在散射区域内为正, 区域外为负的交替分布特性. 对于薄膜负带电, 电子会输运至导电衬底形成泄漏电流, 其暂态过程随泄漏电流的增加趋于平衡. 而正带电暂态过程随返回二次电子的增多而趋于平衡. 在平衡态时, 负带电表面电位随薄膜厚度、陷阱密度的增大而降低, 随电子迁移率、薄膜介电常数的增大而升高;而正带电表面电位受它们影响较小.

Charging effects of SiO2 thin films under defocused electron beam irradiation

Based on a three-dimensional self-consistent numerical model with consideration of electron scattering, trapping and transport, the charging effects due to low-energy defocused electron beam irradiation are simulated for a SiO₂ thin film with a grounded conductive substrate. The results show that because of electron drift and diffusion, electrons can transit the electron scattering region, forming negative space charges. The space charge is, therefore, positive and negative within and outside the scattering region, respectively. Some electrons can flow to the conductive substrate, forming the leakage current, and the transient negative charging process tends to equilibrium as the leakage current increases. In comparison, the transient positive charging process approaches equilibrium with the number of returned electrons increasing due to the positive surface potential. In the equilibrium state, the surface potential of the film negatively charged decreases with film thickness and trap density increasing; it increases with electron mobility and dielectric constant. However, the equilibrium surface potential of the film positively charged varies slightly with film parameter.