Nanolithography on thin layers of PMMA using atomic force microscopy

Abstract

A new technique for producing nanometre scale patterns on thin layers(<30 nm thick) of PMMA on silicon is described. The method consists of inducing the localmodification of the PMMA by applying a positive voltage between the silicon and anatomic force microscope (AFM) tip. At voltages larger than 28 V, it is observed that a holeis directly produced on the PMMA. The silicon surface is simultaneously oxidized even inthe case where a hole has not been created. Monitoring of the electrical current through theAFM tip during the application of the voltage allows elucidating the mechanism of thePMMA removal. The process is used to define nanometre scale electrodes by combining theAFM lithography with electron beam lithography, metal deposition and lift-off processes.