Custom design of optical-grade thin films of silicon oxide by direct-write electron-beam-induced deposition

Abstract

This work describes a rapid fabrication approach of thin silicon oxide films on confined areas by electron-beam-induced deposition. This maskless direct-write process utilizes a localized chemical vapor deposition (CVD) on specific areas utilizing a focused electron beam. The deposition from siloxane vapor in the presence of oxygen is initiated by the energy of an electron beam of 1nm diameter. By scanning the beam, thin films with arbitrary geometries and three-dimensional structures were deposited. In contrast to blanket deposition with conventional methods such as thermal CVD or plasma-enhanced CVD, the lateral confined layers can be fabricated at room temperature. With a maskless process, the final structure is fabricated within a single process step. The process was optimized towards a high deposition rate and high material purity. The influence of process parameters on the deposition efficiency is discussed. A characterization of the chemical composition and of the surface roughness was performed with auger electron spectroscopy, energy-dispersive x-ray, and atomic force microscopy, respectively. The optical properties were investigated by transmission measurement at 248nm. The correlation to processing conditions and the growth mechanism induced by the electron beam is discussed. This work illustrates the flexibility of this maskless method and the potential to control material properties via the process parameters. The fabrication of exemplary structures such as three-dimensional silicon oxide pillars and transparent films illustrates the application potential of this versatile direct-write method.