Atomic force microscope nanolithography on SiO2/semiconductor surfaces

We report on the fabrication of a nanometer-scale SiO2 mask on a semiconductor surface using an atomic force microscope (AFM). Layers of SiO2 5-35 nm thick sputtered on GaAs substrates are covered with very thin polymethyl methacrylate (PMMA) films by spin-coating. The AFM tips were used mechanically to modify the polymer layers. Lines with 18-nm width and holes with 20-nm diameter were successfully patterned on the PMMA films. These patterns were transferred into the SiO2 layers by wet etching in buffered HF. Linewidths as small as 40 nm have been obtained. Arrays of lines and holes with 200 nm periodicity were successfully fabricated.