样品倾转角度对透射电镜表征纳米薄膜的影响  

Effect of Sample Tilting Angle on the Characterization of Nanofilms by Transmission Electron Microscopy

作　　者：张革 崔云[1,2] 赵娇玲[1,2] 王涛[1,2] 赵元安[1,2] Zhang Ge;Cui Yun;Zhao Jiaoling;Wang Tao;Zhao Yuan'an(Laboratory of Thin Film Optics,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;Key Laboratory of Materials for High Power Laser,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China)

机构地区：[1]中国科学院上海光学精密机械研究所薄膜光学实验室,上海201800 [2]中国科学院上海光学精密机械研究所强激光材料重点实验室,上海201800

出　　处：《光学学报》2024年第2期312-317,共6页Acta Optica Sinica

基　　金：国家自然科学基金(12275346);中科院青促会会员项目(2020253)。

摘　　要：以沉积在Si[100]基底的Mo/Si多层膜为例,通过透射电镜(TEM)测量了多层膜在不同倾转角度下的界面结构,并提取了多层膜的周期厚度以及单周期中Mo层和Si层的厚度。结果表明:样品沿α方向倾转时,Mo层和Si层的测量厚度几乎没有变化,但界面粗糙度增大,这是由于旋转时薄膜的厚度方向始终与电子束垂直,而电子束穿过的TEM样品厚度Z增大;样品沿β方向倾转时,由于倾转时样品截面与电子束不垂直,造成伪影严重,无法区分Mo层和Si层,多层膜的测量总厚度随倾转角的增大先增大后减小。此外,提出了样品沿β方向倾转后测量薄膜厚度的计算公式。对于较薄的薄膜,随着倾转角β的增大,测量厚度增大;对于较厚的薄膜,随着倾转角β的增大,测量厚度先增大后减小。薄膜厚度t0越小,沿β方向倾转后测量厚度的相对误差越大。当TEM样品厚度Z为10 nm时,沿β方向倾转后测量厚度的相对误差较小。Objective Accurate characterization of Mo/Si multilayer film thickness is important for process iteration and analysis.As one of the visualization methods,transmission electron microscopy(TEM)can characterize the thickness of nanofilm deposited on a single crystal Si wafer.It can be calibrated internally through the Si substrate lattice parameters,which is very accurate.However,if we do not pay attention to the crystal orientation of the Si substrate during TEM characterization or we use amorphous substrate materials such as fused quartz,it is difficult to ensure that the cross-section of the sample is exactly perpendicular to the electron beam.As a result,the two-dimensional projection imaging of threedimensional samples produces artifacts,resulting in unknown measurement errors.Therefore,it is of great significance to study the influence of sample tilting angle on the TEM characterization of nanofilms.Methods Mo/Si multilayer films are deposited by pulsed direct current sputtering.Cross-section samples for TEM characterization are prepared by ion milling.TEM images and high-resolution TEM images of the multilayer films are obtained by TEM.The TEM cross-section samples are tilted inαandβdirections by a double tilting holder.Combined with the profile curves of the images,we obtain the thickness of the multilayer film at different tilting angles,the roughness of the interface,and the thickness of the Mo and Si layers in a single period.Results and Discussions As the Mo/Si multilayer film sample tilting in theαdirection,the thickness direction of the film is always perpendicular to the electron beam direction(Z axis),so the thickness does not change.The roughness increases,because the thickness Z of the TEM sample which the electron beam passes increases as tilling in theαdirection.It implies more projective superposition at the interface layer(Fig.4).As tilting in theβdirection,the sample cross-section is not perpendicular to the electron beam direction(Z axis),resulting in artifacts during projection imaging

关 键 词：透射电镜 倾转角度 薄膜界面 膜层厚度 

分 类 号：O4-34[理学—物理]