CMOS-Compatible Catalyst for MacEtch: Titanium Nitride-Assisted Chemical Etching in Vapor phase for High Aspect Ratio Silicon Nanostructures.

Metal-assisted chemical etching (MacEtch) is an emerging anisotropic chemical etching technique that has been used to fabricate high aspect ratio semiconductor micro- and nanostructures. Despite 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 a gold (Au)-based metal catalyst, as Au is a detrimental deep-level impurity in Si. In this report, for the first time, we demonstrate CMOS-compatible titanium nitride (TiN)-based MacEtch of Si by establishing a true vapor-phase (VP) MacEtch approach in order to overcome TiN-MacEtch-specific challenges. Whereas inverse-MacEtch is observed using conventional liquid phase MacEtch because of the limited mass transport from the strong adhesion between TiN and Si, the true VP etch 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. VP MacEtch represents a significant step toward scalability of this disruptive technology because of the high controllability of gas phase reaction dynamics. TiN-MacEtch may also have direct implications in embedded TiN-based plasmonic semiconductor structures for photonic applications.