New High Resolution Liquid Crystal Electron Beam Resists

We report the development of a new family of electron beam resists based on liquid crystalline polysubstituted derivatives of triphenylene. These new resists show excellent performance in terms of both high resolution and high durability to plasma etching. Films of the derivatives have been produced in a controlled manner via room temperature spin coating on hydrogen terminated silicon substrates. The dissolution behaviour of the derivatives in various organic solvents was altered by exposure to a 20 keV electron beam. The solubility of the derivative hexapentyloxytriphenylene, in polar solvents, was substantially increased by electron doses greater than ∼ 3 × 10-4 C/cm2 (positive tone behaviour). Doses greater than ∼ 2.5 × 10-3 C/cm2 led to negative tone behaviour in both polar and non-polar solvents. Other derivatives also demonstrated a reduction in their dissolution rate for doses between ∼ 1 × 10-3 and ∼ 7 × 10-3 C/cm2. The derivative sensitivity was found to be roughly proportional to the molecular mass. Negative tone patterns were found to have an etch durability ∼ 70 % greater than that of a conventional novolac based negative tone resist (SAL601). The performance of these new resists has been demonstrated by the definition of line and space patterns with a resolution of ∼ 14 nm, whilst structures with an aspect ratio of.∼ 50 to 1 were etched into the silicon substrate.