Nanoscale Patterning of Zinc Oxide from Zinc Acetate Using Electron Beam Lithography for the Preparation of Hard Lithographic Masks

An approach is presented for nanoscale patterning of zinc oxide (ZnO) using electron beam (e-beam) lithography for future nanoelectronic devices and for hard lithographic masks. Zinc acetate (Zn4O(CH3COO)6) films were exposed using a scanning electron microscope (SEM), causing decomposition of Zn4O(CH3COO)6 into ZnO. The exposure of Zn4O(CH3COO)6 using an electron beam was successfully utilized to fabricate 12 nm zinc oxide lines with a 40 nm pitch on silicon. The chemical composition of zinc acetate (film before e-beam exposure) and ZnO (film after e-beam exposure) was investigated using X-ray spectroscopy (XPS). The Zn 2p shift peaks and the O 1s contribution confirmed the decomposition of zinc acetate into zinc oxide after exposure. To confirm this transformation into ZnO, the optical band gap of the film was determined and the electrical resistivity of the film was measured. The electrical resistivity and the optical band gap results revealed the transformation into a ZnO film with a band gap of 3.31 eV at room temperature and an electrical resistivity of 91.5 Ω cm. The ZnO patterns were used as a hard mask to etch silicon, and it showed a good selectivity of 27:1 for dry etching silicon using SF6 and C4F8.