Dependence of Tip Depth of Silicon Needles on Fabrication Process Conditions

Abstract

We previously developed a process for fabricating needle-shaped silicons (silicon needles) with a small tip radius and a high aspect ratio. They can be obtained by highly selective anisotropic dry etching, using the oxygen precipitation, that is, the SiO x clusters in the silicon substrate, as etching masks. The SiO x clusters can be generated by nitrogen ion implantation and the subsequent oxidation. In this article, we show the dependence of the tip depth of silicon needles on the fabrication process conditions. From experiments, it was found that the tip depth does not depend on the acceleration energy of the nitrogen ions. Instead, it depends on the temperature of the subsequent oxidation and the deposition rate of the sidewall passivation film which is produced during the dry etching to protect the silicon needles from being side-etched. The reason for the dependences will be discussed.