Sharp Silicon Nano-Needles Based on Boron Etch-Stop in TMAH Solutions

Operations on biological living cells and molecular devices have driven research towards implementation of high-aspect-ratio nano-needles. However, current nano-needle fabrication is complicated to control the sizes and angles. In this work, we develop a simple method to fabricate repeatable and integrated circuit (IC)-compatible sharp silicon nano-needles based on boron etch-stop in tetramethyl ammonium hydroxide (TMAH) solutions, and the needle angles can be accurately controlled. An analytical model is proposed to efficiently predict the needle sizes and explain the etching evolution of silicon nano-needles.