Preparation of Large-Aperture Macroporous Silicon with Controllable Pore Tip Angle on Low-Resistivity p-Type c-Si Substrate by Metal-Catalyzed Electrochemical Etching

Abstract

Macroporous silicon has been widely utilized in many electronic and optoelectronic applications. However, it is quite difficult to prepare macroporous silicon with large aperture on p-type low-resistivity c-Si substrate by the conventional fabrication methods, such as reactive ion etching (RIE), electrochemical etching (ECE), and metal-catalyzed electroless etching (MCEE). Such work was realized here by metal–catalyzed electrochemical etching (MCECE). Firstly, Ag nanoparticle catalyst was fabricated on the c-Si substrate by immersing the substrate into a mixed aqueous solution of HF and AgNO3. Electrochemical etching was then performed in a HF-H2O2 solution. The synergetic effect of Ag catalyst and the external applied electric field successfully facilitated the formation of large-aperture macroporous silicon. By adjusting the specific MCECE conditions, macroporous silicon with the pore aperture large up to several micrometers was successfully obtained on p-type c-Si substrate with the low resistivity of about 0.1–3 ohm·cm. Especially, the pore tip angle could be controlled flexibly from 3.5° to 41°. The pore tip angle enlarged with the increase of the etching current density and was independent on the etching time. Thus, MCECE can provide a potential way to controllably fabricate complex microstructures on low-resistivity p-type c-Si substrate.