高能透射电子束照射聚合物薄膜的带电效应  

Charging effect of polymer thin film under irradiation of high-energy transmission electron beam

作　　者：霍志胜 蒲红斌[1] 李维勤[1,2] Huo Zhi-Sheng;Pu Hong-Bin;Li Wei-Qin(School of Automation and Information Engineering,Xi’an University of Technology,Xi’an 710048,China;Department of Electronic Science and Technology,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安理工大学自动化与信息工程学院,西安710048 [2]西安交通大学电子科学与技术系,西安710049

出　　处：《物理学报》2019年第23期19-28,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11175140);陕西省自然科学基金(批准号:2019JM-340);西安理工大学科研计划(批准号:2015CX030)资助的课题~~

摘　　要：高能透射电子束照射下聚合物薄膜的带电效应严重影响其电子显微学检测的可靠性.采用数值计算方法研究了聚合物薄膜的带电效应.基于Monte Carlo方法模拟了电子的散射过程,采用有限差分法处理电荷的输运、俘获和复合过程,获得了净电荷、内建电场、表面出射电流、透射电流等动态分布特性,分析了薄膜厚度、电子束能量对相关带电特性的影响.结果表明:由于近表面电子的出射,样品内部净电荷、空间电位沿入射方向均呈现先为正、后为负的分布特性,导致部分出射电子返回表面以及内部沉积电子向基底输运形成电子束感生电流;随着电子束照射,由于薄膜带电强度较弱,透射电流随时间保持不变,实际出射电流及样品电流分别下降和上升至一个稳定值.薄膜厚度的增加使带电过程的瞬态时间增加,引起表面电位下降以及实际出射电流、样品电流增大;电子束能量的升高使透射电流增大,样品电流减小,引起表面正电位下降及实际出射电流的减小.The serious charging effect of polymer film with a thickness of the order of microns under the radiation of high-energy transmission electron beam, on the reliability of the micro-nano electronic device in electron microscopy detection is investigated. The charging effect of the polymer film is numerically calculated in this paper. The scattering process is simulated by the Monte Carlo method. The elastic scattering is calculated with the Rutherford scattering model. The inelastic scattering is simulated with the fast secondary electron(SE)model and the Penn model. The transport, the capture, and the recombination process of the charges are treated with the finite difference method. The fourth-order Runge-Kutta method is used to solve the trajectory of the emitted SEs. The dynamic distributions of the net charge, the built-in electric field, the surface emission current, and the transmission current are investigated, and the influence of the film thickness and the beam energy on the charging characteristics are analyzed. The results show that due to the emission of electrons near the sample surface, the distribution of the net charge in the sample is first positive and then negative along the incident direction. In addition, under the irradiation,higher charge quantity is deposited in the sample, and the net charge density increases gradually. However, with long-time irradiation, the deposited electrons transport to the surface under the action of built-in electric field which reduces the surface net charge density. Therefore the net charge density tends to a stable value. The space potential is positive in the surface and negative inside the sample. Therefore some emitted SEs return to the surface, resulting in the electron beam-induced current. With the irradiation, the positive surface potential increases and tends to a stable value. Hence the actual surface emission current decreases to a stable value and the sample current increases to a stable value. The sample current remains unchanged due to the weak char

关 键 词：带电效应 数值模拟 透射电流 输运 

分 类 号：TB3[一般工业技术—材料科学与工程]