Exposing submicron patterns with a variable shaped electron beam machine

Abstract

There are several problems with exposing submicron patterns with the variable shaped electron beam machine. One is the proximity effect caused by the backscattered electrons from the resist and substrate. The other is the shape edge slope of the beam profile caused by the Coulomb effect, and the third is the variation of beam current density with beam size. The edge resolution depends on the shape edge slope and it is varied with the shaped beam current density and shaped beam size as discussed in this paper. Some experiments on the edge resolution have been performed by using the JEOL JBX6AII machine. Some problems such as underexposure, beam spot underlapping, and pattern infidelity in the submicron range are also discussed. It is indicated that a shape edge resolution of 0.15 μm is required for exposing 0.4 μm pattern. In order to decrease the influence of the proximity effect and improve the shape edge resolution, a series of measures on the column adjustment and the exposure parameter selection must be taken. An adjustment method which causes the increase of the shaped beam current density with a decrease of the shaped beam size has been used for partially correcting the proximity effect. Submicron patterns with 0.4 μm linewidth on the Cr plate coated with positive resist OEBR‐1000 and on the wafer coated with EBR‐9 have been obtained.