LOW-VOLTAGE ALTERNATIVE FOR ELECTRON-BEAM LITHOGRAPHY

The current trend in electron beam lithography for patterning submicron features is towards the use of higher beam voltages (20-100 keV). Among the problems often perceived to be associated with the use of low voltages are the poorer resolution, the lower brightness, and the greater sensitivity to electric and magnetic interference. Both by simulation and by experiment at 2 kV it is shown: (1) features of less than 100 nm are clearly resolved iii resist of about the same thickness; (2) such features are clearly resolved in both sparse and dense pattern; (3) such features in sparse and dense areas are clearly resolved over a twofold range of exposure doses; (4) such delineation is largely independent of substrate material; (5) there is no evidence of alternating-current magnetic interference: (6) the lower beam brightness at low voltages is compensated by the increased sensitivity of resists to lower energy electrons. The remaining concerns about low voltage lithography are the reliability of resist with an imaging layer less than 100 nm thick and the extent and effect or charging of such a resist.