Nanofabrication of high aspect ratio (∼50:1) sub-10 nm silicon nanowires using inductively coupled plasma etching

Abstract

The development of nanofabrication techniques for creating high aspect ratio (∼50:1) sub-10 nm silicon nanowires (SiNWs) with smooth, uniform, and straight vertical sidewalls using an inductively coupled plasma (ICP) etching process at 20 °C is reported. In particular, to improve the quality and flexibility of the pattern transfer process for high aspect ratio SiNWs, hydrogen silsesquioxane, a high-resolution, inorganic, negative-tone resist for electron-beam lithography has been used as both the resist for defining sub-10 nm patterns and the hard mask for etching the underneath silicon material. The effects of SF6/C4F8 gas flow rates, chamber pressure, platen power and ICP power on the etch rate, selectivity, and sidewall profile are investigated. To minimize plasma-induced sidewall damage, moderate plasma excitation power (ICP power of 600 W) and low ion energy (platen power of 6–12 W) were used. Using the optimized etch process at room temperature (20 °C), the authors have successfully fabricated sub-10 nm SiNWs, which have smooth vertical sidewall profile and aspect ratios up to ∼50:1. This optimized etch combined with a controlled thermal oxidation allows the realization of consistent, reproducible, and reliable SiNW devices with nominal widths from 100 nm down to sub-5 nm in silicon on top of SiO2 fabricated on silicon on insulator substrates.

Analysis of Ge micro-cavities with in-plane tensile strains above 2 %

“…The structures were subsequently dry etched in a mixed SF 6 and C 4 F 8 recipe through to the Si layer, with an etch recipe which has previously demonstrated low electrical [18,19] and optical damage [4] to devices. A wet etch in tetramethylammonium hydroxide (TMAH) and isopropyl alcohol (IPA) was used to selectively etch the Si thereby undercutting the structures.…”

Germanium-on-silicon waveguides for mid-infrared photonic sensing chips

“…The grating coupler and rib waveguides were dry etched at the same time using a mixed gas process (SF6 / C4F8). This etch process has been optimized to be highly anisotropic and to produce ultra-smooth sidewalls [5]. Next a trench is etched through the remaining Ge slab at the output facet of the rib waveguide, before an SU8 polymer block is subsequently patterned and cured.…”

Fabrication of mid-infrared plasmonic antennas based on heavily doped germanium thin films

“…The process was optimised to obtain a vertical sidewall profile, minimum edge roughness and a reasonably fast etching time, which we reached with a flux of 30/90 sccm for SF 6 /C 4 F 8 . The platen power was set to 12 W, the coil power to 600 W and the pressure was set to 1.6 Pa [22]. The etching process was assisted by a laser interferometer detection system to stop the process at the interface between the germanium and the silicon.…”