具有可变真空结构的物镜优化设计及性能分析  

Optimized Design and Performance Analysis of Objective Lenses with Variable Vacuum Structures

作　　者：史丽娜 王鹏飞 刘俊标[1,2] 王岩 殷伯华 韩立[1,2] Shi Lina;Wang Pengfei;Liu Junbiao;Wang Yan;Yin Bohua;Han Li(Institute of Electrical Engineering,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院电工研究所,北京100190 [2]中国科学院大学,北京100049

出　　处：《光学学报》2024年第5期193-202,共10页Acta Optica Sinica

基　　金：微纳加工技术共性关键技术研发团队项目(GJJSTD20200003);广东省重点领域研发计划(2020B0101320002)。

摘　　要：环境扫描电子显微镜(ESEM)能够在低真空环境模式下对含水、含油以及生物等样品进行高分辨率观测。由于电子束通道与样品室间存在着极大的真空压差,采用真空差分结构会导致出现物镜的工作距离增加、偏转范围缩小、电子束和气体碰撞概率增加等问题,最终影响成像分辨率和效率。针对这些问题,本文从电子光学理论出发,综合考虑了ESEM中物镜结构和真空差分结构,将两者结合在一起进行优化设计,提出了一种具有可变真空结构的物镜设计方法,并搭建了实验平台,开展了物镜磁场测试、真空压差测试和分辨率测试。测试结果表明,在目前实验条件和133 Pa的低真空环境模式下,工作距离为15 mm时,20μm×20μm的扫描场对应的成像分辨率优于50 nm。Objective Environmental scanning electron microscopes(ESEMs)are widely employed for high-resolution observation of water containing,oil containing,and biological samples in low vacuum environments.However,at present,the development of ESEMs in China is almost blank,and most of them need to rely on imports.Therefore,the research on ESEMs can help improve China s independent development capability in this field,and provide a theoretical and experimental basis for the development of ESEMs in the future.Compared with conventional electron microscopy,the sample chamber of ESEMs should be in a low vacuum or ambient state.The vacuum value is generally on the order of 100 Pa,while that of the electron beam channel and the electron gun needs to be less than 1×10^(-3)Pa and 1×10^(-7)Pa respectively.The pressure difference between the electron beam channel and the sample chamber is much larger than that between the electron gun and the electron beam channel.The conventional method is to add a throttle tube between the electron beam channel and the sample chamber.Meanwhile,since the large pressure difference remains much greater than that between the electron gun and the electron beam channel,the conventional method is to add a throttle tube between the electron beam channel and the sample chamber,but the large pressure difference will result in a long throttle tube with a small aperture.This will bring practical problems in imaging,such as the longer throttle tube leading to an increase in the working distance of the objective lens.As a result,it increases the spherical aberration,reduces the imaging resolution,and causes a smaller deflection range to a certain extent.Additionally,the long throttle tube will lead to the presence of residual gas inside the tube,the electron beam will drift in a section of the gas space where there is low gas pressure,and the probability of collision between the electron beam and the gas is high,which will have a greater effect on the resolution at low accelerating voltages.Therefore,the co

关 键 词：电子光学 物镜 可变真空结构 压差光阑 节流管 

分 类 号：TN16[电子电信—物理电子学]