Optimum energy for high resolution low voltage electron beam lithography — Monte Carlo simulations and experiments

Abstract

The electron backscattering coefficients of thin tri-level-process layer systems in the energy range from 2.5 to 40.0 keV have been calculated by Monte Carlo simulations. The results show a significant variation of the backscattering with the primary electron energy and the atomic number of the materials used in the layer systems. A local backscattering minimum in the region of 4–5 keV has been found for the investigated multilayer systems. Its stability to variations of the layers' parameters has been investigated. First high resolution experiments at 5.0 keV primary electron energy were carried out to determine the minimal achievable grating period with line-to-space ratio of 1:1. Using ZEP-7000 and hexaacetate p-methylcalix[6]arene resist gratings with 60 and 50 nm minimum period, respectively, were manufactured.