Resists and processes for 1 kV electron beam microcolumn lithography

Low-voltage electron beam lithography has been considered for some time for high-resolution lithography because of reduced proximity effects, increased resist sensitivities, and reduced substrate damage. An accelerating voltage of 1 kV is being considered for the operation of microcolumns that are being developed for use in an innovative, high-speed, high-resolution electron beam lithography system. The development of resists and processes for use at 1 kV then becomes one of the essential components in this developing technology. Since 1 keV electrons have a penetration depth of approx.60 nm in organic polymers, the resists used for electron beam exposures must be correspondingly thin. This makes the development of processes for pattern transfer a challenge. Here, we report on three resist and processing schemes for use at 1 kV which can be used to produce 50-100 nm wide structures. Structures as small as 50 nm wide with 3 to 1 aspect ratios, and trenches 300 nm deep and less than 100 nm wide have been successfully transferred into Si substrates. Despite the use of very thin resists, the transferred patterns do not suffer from noticeable defects.