A BACKGROUND DOSE PROXIMITY EFFECT CORRECTION TECHNIQUE FOR SCATTERING WITH ANGULAR LIMITATION PROJECTION ELECTRON LITHOGRAPHY IMPLEMENTED IN HARDWARE

A background dose proximity effect correction procedure is proposed th at utilizes the unique way image contrast is formed in scattering with angular limitation projection electron lithography (SCALPEL (R)). An electron beam is selectively scattered by a thin, high atomic number l ayer patterned on a membrane mask Some of the scattered radiation, whi ch is normally blocked at an aperture to form contrast at the wafer, i s allowed to pass through the system optics. Nominally dark regions of the mask are therefore allowed to expose the resist on a wafer. Howev er, because the scattered radiation enters the projection system at re latively large angles, it is subjected to system aberrations and is im properly focus ed at the wafer. This dispersed radiation mimics the na tural long range backscatter exposure emanating from the intentionally exposed regions, and ideally results in a constant background exposur e in the resist-similar to the GHOST background correction technique u sed in direct-write applications; However, unlike the direct-write cor rection, both the primary exposure and the correction exposure are ach ieved at the same time. Throughput is not reduced by the correction. A lthough the correction dose profile may not resemble the form of the l ong range backscatter energy deposition in the resist, the deviations of background exposure are small for mask patterns of practical intere st, in comparison with the variation of uncorrected exposures of the s ame pattern. (C) 1995 American Vacuum Society.