Abstract
Precise measurements of focused electron beam diameters are usually performed by measuring the beam current distribution using a mechanical knife edge line scan. In the measurements, the positioning resolution of the knife edge affects the beam diameter accuracy, which is not so highly reliable because of the difficulty of the installation of a precise measurement instrument in the vacuum chamber of scanning electron microscopes (SEMs). Against this backdrop, a compact laser interferometer with a piezodriven micro mechanical scanner is installed in an SEM to realize accurate knife edge positioning. The interferometer has a resolution of 0.4μm (1/1600 of He-Ne laser wavelength - 0.633μm), which corresponds to the sampling interval of the current distribution measurement. From experimental results for different acceleration voltages and probe currents, a maximum standard deviation of the measurement of 3nm was obtained for beam diameters of a couple nm through dozens of nm.
