Silicon Nanostructuring Using SF6/O2 Downstram Plasma Etching: Morphological, Optical and Sensing Properties

Abstract

Silicon (Si) nanostructures were prepared in the downstream of radiofrequency SF 6 /O 2 mixture plasma generated in 13.56 MHz hollow cathode discharge system. Depending on the oxygen percentage in the mixture, the obtained Si nanostructures were characterized for their different properties: etching rate, morphology, optical reflectance, photoluminescence, spectral response and humidity sensing. It is found that the etching rate exhibits a maximum value when the O 2 ratio reaches 5%. An interesting defect-induced "violet" luminescence is reported from the Si nanostructures, whose intensity depends on their density. The obtained Si nanostructures have shown to induce a spectral response (SR) enhancement, in comparison with a smooth Si substrate, of about 100 times at 1100 nm wavelength. A very short response time (1 sec) to the humidity was measured for 5% O 2 in the SF 6 /O 2 plasma mixture, which was found to be well-correlated with the porosity of the Si nanostructures.

Effect of surface modification on the properties of plasma‐polymerized hexamethyldisiloxane thin films

“…Commercial Ar and He gases with 99.999% purity, SF 6 gas (99.99% purity), O 2 gas (99.9999% purity), and HMDSO (from Sigma‐Aldrich) with 98% purity grade have been used in our experiments. Since our system is a remote plasma configuration, therefore, the concentrations of ions and electrons are relatively low and the concentration of free radicals is relatively high in the remote region far from the primary plasma …”

“…Since our system is a remote plasma configuration, therefore, the concentrations of ions and electrons are relatively low and the concentration of free radicals is relatively high in the remote region far from the primary plasma. 28…”

“…Van Hest et al and Rich et al reported that atomic oxygen reacts easily with SiCH 3 , SiH, Si, and CH 3 groups of the pp‐HMDSO film. SF 6 plasma, providing the reactive etchant fluorine atoms, was previously and successfully used for the enhancement of polymers hydrophobicity, while for pp‐HMDSO thin film surface modification, an elevated etching rate (≈90 nm/min) of this material in SF 6 plasma was reported, making it a potential candidate in the area of designing high–aspect ratio microelectromechanical systems…”

“…27 Van Hest et al 20 and Rich et al 25 reported that atomic oxygen reacts easily with Si-CH 3 , Si-H, Si, and CH 3 groups of the pp-HMDSO film. SF 6 plasma, providing the reactive etchant fluorine atoms, 28 was previously and successfully used for the enhancement of polymers hydrophobicity, [29][30][31] while for pp-HMDSO thin film surface modification, an elevated etching rate (≈90 nm/min) of this material in SF 6 plasma was reported, making it a potential candidate in the area of designing high-aspect ratio microelectromechanical systems. 32 The technological motivation behind our present work, which deals with the surface modification of pp-HMDSO thin films by two reactive plasmas (SF 6 and O 2 plasmas), is to investigate, besides the already reported properties mentioned above, particularly in O 2 plasma, other films properties, such as film density and thickness, optical band gap, and electrical resistivity.…”

The Reflectance Characteristics of an Inverse Moth-Eye Structure in a Silicon Substrate Depending on SF6/O2 Plasma Etching Conditions

“…Under pure SF 6 plasma, the etch rate of the silicon substrate is about 530 nm/min, and the surface roughness (root mean square, RMS) is 85.74 nm. As the amount of O 2 gas is increased, the etch rate and surface roughness goes through a maximum and slightly decrease [ 36 , 37 ]. The etch rate and the roughness were at their maximum of 780 nm/min and 104.41 nm, respectively, when 20 sccm of O 2 gas was added.…”