改善场发射扫描电镜分辨本领的原理和展望

Principle and prospect to improve the resolution of field emission scanning electron microscope

本文讨论了改善场发射扫描电镜分辨本领的原理。分析结果表明 ,仪器的分辨本领主要依赖于物镜的球像差系数 Cs。如果等效球像差系数能降低到 0 .1× 10 -2 cm的水平 ,则二次电子像的分辨本领为 0 .3 2 2 nm(当扫描电子束的加速电压 VA=3 0 k V)。此外 ,在 Cs=0和扫描电子束的半开角 α=5× 10 -2 rad,本文估计场发射扫描电镜的极限分辨本领可望达到 0 .178nm(当 VA=3 0 k V)。

In present paper, the principle to improve the resolution of FE-SEM ha s been discussed. The analysis results indicate that the resolution of the instr ument mainly depends on C s ( C s—the spherical aberration coefficient o f the objective lens).If the equifinal spherical aberration coefficient can be d ecreased to the level of 0.1×10 -2 cm, the resolution of the secondary elec tron image would be about 0.322 nm at V A=30kV. Furthermore, the limit res olution of FE-SEM evaluated by present paper can be achieved to the level of 0. 178 nm at V A=30kV under the conditions of C s=0 and α =5×10 -2 rad. (α—the semi-angle of the scanning electron beam).