Formation of nanometer-scale structures in SiO2 thin films by means of MeV-ion irradiation

Abstract

Future nanometer-scale electronic applications will require the engineering and modification of new materials on the atomic and molecular scale. In this article, we explore the possibility of using MeV heavy-ion irradiation to induce physical modifications on the materials of choice of the existing microelectronic technology, such as SiO2, metals and silicon, to form nanometer-scale structures. Micrometer-sized trenches or H-shaped structures were machined using focused ion-beam milling in Al/SiO2 and Au/SiO2 bilayers on crystalline Si. These samples were irradiated with a 4.6 MeV O2+ beam at room temperature, and the structures were studied by scanning electron microscopy. The micrometer-scale SiO2 structures underwent an anisotropic deformation induced by the electronic energy loss of the MeV incoming ions, leading to a major flow of SiO2 which fills the trench region. The target dimensions perpendicular to the beam direction increased, and the trench width or the micrometer-sized gaps of these structures decreased down to the nanometer scale as a function of the ion fluence. In the case of Al/SiO2 and Au/SiO2 bilayers, only the SiO2 film underwent the plastic deformation, and there is no flow of either the silicon substrate or the metallic layer.