ACS applied materials & interfaces | 2019
CMOS Compatible Catalyst for MacEtch: Titanium Nitride Assisted Chemical Etching in Vapor Phase for High Aspect Ratio Silicon Nanostructures.
Abstract
Metal-assisted Chemical Etching (MacEtch) is an emerging anisotropic wet chemical etching technique that has been used to fabricate high aspect ratio semiconductor micro- and nanostructures. Despite of its advantages in unparalleled anisotropy, simplicity, versatility, and damage-free nature, the adaptation of MacEtch for silicon (Si) based electronic device fabrication process is hindered by the use of gold (Au)-based metal catalyst, as Au is a detrimental deep level impurity in silicon. In this report, for the first time, we demonstrate CMOS compatible titanium nitride (TiN)-based MacEtch of silicon by establishing a true vapor phase MacEtch approach in order to overcome TiN-MacEtch specific challenges. While inverse-MacEtch is observed using conventional liquid phase MacEtch due to the limited mass transport process resulted from the strong adhesion between TiN and Si, the true vapor phase MacEtch leads to forward MacEtch and produces Si nanowire arrays by engraving the TiN mesh pattern in Si. The etch rate as a function of etch temperature, solution concentration, TiN dimension, and thickness is systematically characterized to uncover the underlying nature of MacEtching using this new catalyst. Vapor Phase MacEtch represents a significant step towards scalability of this disruptive technology because of the high controllability of gas phase reaction dynamics. It may also have direct implications in embedded TiN-based plasmonic semiconductor structures for photonic applications.