Mass transfer analysis of a concentration-regulated metal-assisted chemical etching system and its application in Si nanohole fabrication

Abstract

This study aims to characterize the mass transfer characteristics of a novel concentration-regulated metal-assisted chemical etching (MACE) system and investigate its application in the controllable fabrication of ∼ 600 nm diameter silicon (Si) nanohole arrays. A concentration-regulated MACE system for Si nanohole etching is established, and the CFD simulations of fluid flow, mass fraction evolution, and mass transfer are conducted. Results reveal that the mass fraction distributions from simulations and experiments are in good agreement. As the inlet velocity increases, the average velocity and vorticity significantly increase, the mass fraction approaches the target concentration more quickly, and the mass transfer coefficient increases by 1.51 to 6.72 times compared to conventional MACE. The concentration-regulated MACE system with a fine pore array demonstrates good concentration regulation performance due to its stable mass fraction evolution process, minimal standard deviation of mass fraction, and uniform mass transfer coefficient. Utilizing the concentration-regulated MACE system, the etching rate of Si nanoholes increases by approximately 27.78 % under mass transfer enhancement, and large-area, uniform, high aspect ratio, and controllable tortuous Si nanohole arrays are successfully fabricated for the first time.