ELECTRON-BEAM BLANKER OPTICS

Closed form analytic solutions for electrons interacting with a double-deflection blanker have been developed and implemented as a c-language program. The double-deflection blanker has a transmission line connecting the upper and lower pairs of plates, which can reduce beam positional jitter when the signal propagation time is correctly set. Several proposed design rules for setting the delay time in terms of blanker geometry are evaluated, but these are shown to be insufficient to determine the optimum. A damped cosine function represents the voltage produced by the blanking circuit and models ringing, overshoot, and slew rate. The onset of current transmission is related to blanker voltage and aperture size. The fringe field effect can be accounted for by combining the analysis with an experimental measurement of blanker sensitivity to determine the effective blanker plate length. The design is able to support 160 MHz blanking and 7.5 V/ns slew rate in a 10-kV electron beam lithography system and maintain 0.01-mu-m positional accuracy over the entire exposure.