Scaling the Aspect Ratio of Nanoscale Closely Packed Silicon Vias by MacEtch: Kinetics of Carrier Generation and Mass Transport

Abstract

Metal-assisted chemical etching (MacEtch) has shown tremendous success as an anisotropic wet etching method to produce ultrahigh aspect ratio semiconductor nanowire arrays, where a metal mesh pattern serves as the catalyst. However, producing vertical via arrays using MacEtch, which requires a pattern of discrete metal disks as the catalyst, has often been challenging because of the detouring of individual catalyst disks off the vertical path while descending, especially at submicron scales. Here, the realization of ordered, vertical, and high aspect ratio silicon via arrays by MacEtch is reported, with diameters scaled from 900 all the way down to sub-100 nm. Systematic variation of the diameter and pitch of the metal catalyst pattern and the etching solution composition allows the extraction of a physical model that, for the first time, clearly reveals the roles of the two fundamental kinetic mechanisms in MacEtch, carrier generation and mass transport. Ordered submicron diameter silicon via arrays with record aspect ratio are produced, which can directly impact the through-silicon-via technology, high density storage, photonic crystal membrane, and other related applications.

Interfacial Contact is Required for Metal‐Assisted Plasma Etching of Silicon

“…Si covered by the noble metal catalyst etches significantly faster than uncovered Si, transferring the pattern of the deposited metal catalyst to the underlying Si. MACE proceeds through electrochemical and mass transport reactions predicated on the reduction of H 2 O 2 at the metal surface and extraction of electrons from underlying Si, thus injecting holes, at the Si–metal interface to create electron‐poor depletion regions in Si that are more susceptible to etching by HF …”

Highly Efficient Nano-Porous Polysilicon Solar Absorption Films Prepared by Silver-Induced Etching

“…Another facile method to control the morphology of texture structure on the surface of Si materials is metal-assisted chemical etching (MaCE) [6,7]. The nanowires or micropillars [8], vertical trenches [9], or via array structures [10,11] can be obtained by controlling the size and the distribution of metal catalyzed particles or films, and the concentration of oxidants (typically hydrogen peroxide, H 2 O 2 ) and hydrofluoric acid (HF). The metal catalyst is a micro-cathode, which reduces H 2 O 2 on the metal catalyst surface into H 2 O and holes that are generated in the metal catalyst.…”

“…The metal catalyst is a micro-cathode, which reduces H 2 O 2 on the metal catalyst surface into H 2 O and holes that are generated in the metal catalyst. The generated holes inject from metal catalyst into Si, which induce the dissolution of Si volumes surrounding metal catalyst by HF [6,7,9,10]. The MaCE process incudes two mechanisms of the mass transport (MT) of reactants and products, and the charge transport (CT) of generation and recombination of holes [9,10].…”

“…The generated holes inject from metal catalyst into Si, which induce the dissolution of Si volumes surrounding metal catalyst by HF [6,7,9,10]. The MaCE process incudes two mechanisms of the mass transport (MT) of reactants and products, and the charge transport (CT) of generation and recombination of holes [9,10]. The geometry of metal catalyst controls MT, while the concentration of H 2 O 2 and HF dominates CT [9,10].…”

“…The MaCE process incudes two mechanisms of the mass transport (MT) of reactants and products, and the charge transport (CT) of generation and recombination of holes [9,10]. The geometry of metal catalyst controls MT, while the concentration of H 2 O 2 and HF dominates CT [9,10]. Large size metal catalyst limits the reaction near the center of metal/Si interface.…”