Fast nanopatterning of two-dimensional photonic crystals by electron beam lithography

A non-conventional low energy electron beam lithography technique for fast patterning of PMMA electron resist is presented for the fabrication of two-dimensional photonic crystal (2D-PC) devices, such as micro-cavity lasers and waveguides. Our technique consists of a single exposure to a large defocused Gaussian beam instead of the conventional pixel-by-pixel mode of approach, in which each feature is composed of an array of smaller focused spots. Experimental results are provided, which show the accurate control of the hole size with the exposure time, for different values of defocusing length. The advantages of our approach include higher (5 to 10 times) exposure speed and reusability of the same scan description for the definition of photonic crystals with different filling factors and the same lattice period. The resulting 2D-PC patterns, having the lattice period of 300 nm and radii in the range of 30-140 nm, have been morphologically characterized by scanning electron microscopy. Monte Carlo simulations of electron scattering in the resist have been carefully performed for both kinds of exposure techniques using a low energy electron beam.