SEM工作距离和加速电压对图像分辨率的影响

摘要

实验证明大工作距离和低加速电压会使SEM较高放大倍数的图像清晰度下降.理论研究表明,SEM图像分辨率主要取决于电子束斑和信噪比的大小,大工作距离会使电子束斑增大；低加速电压会使电子枪亮度下降、电子束流和信噪比减小,从而造成图像分辨率和图像清晰度下降.对于传统SEM,通过减小物镜光阑(电子枪栅极、阳极间距),可对大工作距离(低加速电压)时图像清晰度的提高有一定帮助,但要从根本上解决,必须采用场发射电子枪.%The experiment results show that a large work distance and low acceleration voltage can decrease the SEM image definition at higher magnification.Theoretically, the SEM image resolution mainly depends on the electron beam diameter and the SNR value.Large work distance will increase the electron beam diameter and low acceleration voltage will decrease the electron gun brightness and SNR value.Accordingly, the two aspects cause the image resolution and definition to decrease.For traditional SEM, the application of the field emission electron gun is the fundamental solution to improve the image definition, although the reduction of the object lens aperture and the spacing between grid and anode of the electron gun can play a positive role.