Fabrication and characterization of a miniaturized octupole deflection system for the MEMS electron microscope

This article describes a miniature electron beam scanning system based on an octupole electrode as the key stage of the implementation of the MEMS electron microscope. The scanning system consists of a silicon electrode with a central hole, containing 8 properly powered elements and a special electronic system controlling voltage. Octupole electrode was made using MEMS technology. First, it was examined using computer simulations, and then the operation of the octupole system was tested using a reference electron beam in the SEM JEOL microscope. The scanning system parameters depend on the electron beam energy, distance between the octupole and the sample, and the applied voltage. It is possible either to obtain an octupole scanning system resolution of 27 nm (for electron beam energy E = 4 keV and octupole observation plane distance H = 1 mm) or a large scanning area up to 2.7 mm (E = 4 keV, H = 20 mm), without any significant distortion of the sample image. Subsequently, the first model of the MEMS electron microscope microcolumn was assembled, containing the field-emission cathode, an extraction electrode, a focusing electrode, an octupole electrode, and an anode. The first images of the observed hexagonal metal grid placed on the silicon anode were recorded inside a reference high vacuum chamber.