Blanked aperture array for parallel electron beam lithography

Abstract

The blanked aperture array (BAA) is a technique for improving the throughput of electron beam lithography tools by utilizing a much larger fraction of the electron source current than single probe forming systems. The fabrication of a BAA employs standard MEMS processing. Equations are derived which optimize the blanker performance under specified constraints on source emittance and brightness and blanker modulation frequency. An electron optics column is designed to illuminate the BAA and image it onto the target. For 0.1 μm lithography at 50 kV, an objective working distance of 30 mm and a 5 mrad convergence angle, a total current of 1 μa can be delivered to the target before beam blurring due to Coulomb interactions becomes unacceptable. An electron source of brightness 2×106 A/cm2/Ω and emittance 24 μm mrad can deliver this current through a 660 beamlet BAA at a 100 MHz modulation rate.