Improving the speed of scanning electron microscope deflection systems

Abstract

A simple technique to characterize the response of a SEM deflection system is described. By measuring the delay in the SEM video signal as the primary beam is deflected and swept over a knife-edge, the transient deflection response can be mapped out. The transfer function of the beam deflection is then approximated by exponential functions and appropriate analogue filters are designed to pre-emphasise the deflection coil drive signal in order to increase the deflection speed. This technique is used to decrease the deflection response time from typically ∼6 μs to ∼0.5 μs, thereby allowing the implementation of non-raster scanning schemes that require fast point-to-point deflection.