A high-speed, high-precision electron beam lithography system (electron optics)

Abstract

A variably shaped electron beam exposure system HL‐600 has been developed for both direct wafer writing and mask making. It was designed as a high‐throughput tool to cover lithography requirements down to a 0.5 μm linewidth. To achieve this high‐throughput capability, many newly developed techniques were adopted in the electron optics and in the control electronic circuits. The simplified electron beam column consists of only four magnetic lenses. The magnetic deflection for main field scanning was enlarged so as to reach up to 6.5 mm sq in order to reduce the overhead time associated with work stage movement. In addition, the design of an objective lens system with a small aberration, and an algorithm for deflection aberration correction were developed. Automatic measurement of defocusing and astigmatism aberrations at a number of sample points were performed by taking through focusing, and the third order polynomial correction function of deflection was determined. As a result, the edge resolution for the 2 μm sq beam was less than 0.2 μm over a 6.5 mm sq field. The column uses a flat‐top‐type LaB6 electron gun with high brightness and large emittance. Although the maximum beam size and current density were limited by Coulomb blurring, the gun realizes a 6.4 μm sq size and 10 A/cm2 density at the same time. It typically has a 5000 h lifetime. This HL‐600 is capable of writing more than ten 4 in. wafers per hour on the average. In addition to a summary of the HL‐600 system, this paper describes details concerning the novel techniques in optics and some exposure results.