电子束大扫描场偏转系统设计中,像差的确定是一个必须解决的实际问题。以SDS-3电子束曝光机的磁复合偏转系统为基础,以双通道扫描原理进行扫描,分析了像差与电子束主轨迹的关系。给出了可动物镜的条件,并利用这一条件分析电子束最佳轨迹的结构和方法。并使用计算机辅助设计研究电子束曝光机聚焦偏转系统的结构。由该电子束曝光机试验结果表明,复合系统结构简单紧凑,像差小而可以不用动态校正。采用矢量描写电子轨迹,以积分式表示像差。以0.005 rad半张角,5×10-5的高压纹波,50 mm的像距,10 mm×10 mm扫描场的边脚处,使动态校正前的总像差为0.03 μm。

In the design of electron beam deflection system with a large scanning field, determination of aberration is a practical problem. The relationship between the principal trajectory of electron beam exposure and aberrations has been investigated in combined round magnetic lenses and deflection system of SDS-3 electron beam machine. The double passageway principle in scanning system is used. Conditions of moving objective lens (MOL) are given and used for improving the performance of electron beam scanning system. The construction and the way to obtain the best trajectory have been analyzed. The structure of the electron beam focusing and deflection system of electron beam exposure machine is analysed with computer-aided design (CAD). The result of scanning system of this electron beam exposure machine indicates that the aberration of superimposed focusing-deflection system is so small that the dynamic correction is unnecessary. The electron trajectories are parameter of electrostatic deflection described in the vector form, the aberrations and structure equation are described in the integral form. The arrangement with 50 mm working distance at the 10 mm×10 mm deflection field with 0.005 rad aperture and 5×10-5 beam voltage ripple produces a total aberration disk of 0.03 μm before dynamic correction.