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 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.

Producing Microscale Ge Textures via Titanium Nitride‐ and Nickel‐Assisted Chemical Etching with CMOS‐Compatibility

“…Two types of the inverted pyramid array were prepared as illustrated in the blue and green boxes in insets of Figure 7. Since TiN catalyst is hard to remove by chemicals without damaging Ge, [22] we characterized the inverted pyramid array (width/spacing: 6/2 µm) with the platform area covered by TiN (Figure 2a), marked as Pyramid (TiN) in Figure 7. Sample marked as Pyramid in Figure 7 was the one without Ti/Ni catalyst.…”

“…[24] This puts forward difficulties for forward MacEtch where the catalyst sinks down while etching occurs. [22] However, Ge MacEtch is intrinsically i-MacEtch, [9] which indicates that the usage of TiN might even boost the mass transport and the etching outside TiN covered area. Another potential CMOS-compatible catalyst is nickel (Ni), which has been widely used to form silicide and germanide for low contact resistance.…”

“…[19] These properties make it also suitable as the catalyst which can boost various chemical reactions. [20,21] As the pioneering work employing TiN as catalyst in wet etching, Kim et al [22] have proven its effectiveness in the fabrication of highly ordered Si nanopillars. However, etching characteristic of TiN-MacEtch is different when compared with typical Au-MacEtch.…”

Low dimensional freestanding semiconductors for flexible optoelectronics: materials, synthesis, process, and applications

“…Conventional or deep RIE has employed to fabricate various semiconductor NWs. Recently, metalassisted chemical etching (MacEtch) has drawn much interest as an alternative top-down technique to form various semiconductor nanostructures such as vias, pillars, NWs, pyramids, fins, and nano-groves [33][34][35][36][37]. The typical Si MacEtch starts by depositing the noble metal catalyst on the substrate.…”

Heteroepitaxial β‐Ga2O3 on Conductive Ceramic Templates: Toward Ultrahigh Gain Deep‐Ultraviolet Photodetection

“…[ 15 ] Given its compatibility with complementary metal–oxide–semiconductor (CMOS) processes, low resistivity, high thermal stability, and mechanical durability, TiN has emerged as a particularly critical element in the semiconductor microelectronics industry. It has been used as an electromigration blocking layer for metal interconnects in modern integrated circuit chips, [ 16–18 ] providing conductive channels between a device's metal contacts and its active region while acting as a diffusion barrier to prevent the diffusion of metal atoms into the substrate. TiN crystallizes as a diamond cubic crystal structure (Pearson symbol: cF8; cubic crystal family, all face‐centered with 8 atoms in its unit cell) as sodium chloride (NaCl) does.…”