Nanoscale patterning on insulating substrates by critical energy electron beam lithography

This Letter describes a method to generate nanometer scale patterns on insulating substrates and wide band gap materials using critical energy electron beam lithography. By operating at the critical energy (E2) where a charge balance between incoming and outgoing electrons leaves the surface neutral, charge-induced pattern distortions typically seen in e-beam lithography on insulators were practically eliminated. This removes the need for conductive dissipation layers or differentially pumped e-beam columns with sophisticated gas delivery systems to control charging effects. Using a "scan square" method to find the critical energy, sub-100 nm features in 65 nm thick poly(methyl methacrylate) on glass were achieved at area doses as low as 10 microC/cm2 at E2 = 1.3 keV. This method has potential applications in high-density biochips, flexible electronics, and optoelectronics and may improve the fidelity of low voltage e-beam lithography for parallel microcolumn arrays.