Novel fabrication for vertically stacked inverted triangular and diamond-shaped silicon nanowires on (1 0 0) single crystal silicon wafer

Abstract

The vertical integration of multiple silicon nanowires (multi-SiNWs) has an outstanding ability to enhance drive current, sensitivity and noise immunity by maximizing nanowire density. However, the crystal plane of the SiNW prepared by the present technology for the vertical stacked integration is indeterminate and has plasma damage. In this paper, a novel fabrication method for vertically stacked SiNWs with inverted triangular and diamond-shaped cross-sections on (1 0 0) single crystal silicon wafer is developed and presented, using conventional micromachining processes. The fabrication is based on the crystal plane distribution and anisotropic etching characteristics of (1 0 0) single crystal silicon. An iteration process of self-aligned dry etching and wet etching is first designed to form vertically stacked triangular and diamond-shaped silicon columns. After thermal oxidation thinning and removal of the oxide layer, the vertically stacked triangular and diamond-shaped SiNWs without plasma damage are obtained in the double silicon columns. The vertically integrated approach not only precisely controls the position and shape of the SiNWs but also determines the crystal plane and orientation of the SiNWs. In addition, the triangular and diamond-shaped SiNWs have a larger surface-to-volume ratio than circular and rectangular-shaped SiNWs with the same cross-sectional area and the same length. Therefore, this method can provide a novel, controllable, and economical way to vertically stack more SiNWs with larger surface-to-volume ratio into one chip for high-performance device applications.