The structural and optical properties of black silicon by inductively coupled plasma reactive ion etching

Abstract

Black Silicon nanostructures are fabricated by Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE) in a gas mixture of SF6 and O2 at non-cryogenic temperatures. The structure evolution and the dependency of final structure geometry on the main processing parameters gas composition and working pressure are investigated and explained comprehensively. The optical properties of the produced Black Silicon structures, a distinct antireflection and light trapping effect, are resolved by optical spectroscopy and conclusively illustrated by optical simulations of accurate models of the real nanostructures. By that the structure sidewall roughness is found to be critical for an elevated reflectance of Black Silicon resulting from non-optimized etching processes. By analysis of a multitude of structures fabricated under different conditions, approximate limits for the range of feasible nanostructure geometries are derived. Finally, the technological applicability of Black Silicon fabrication by ICP-RIE is discussed

Self-organized, effective medium Black Silicon for infrared antireflection

“…Besides the possibility to fabricate periodic ARS by deterministic methods [3,4,5,6], in the case of silicon as substrate material also statistical "Black Silicon" ARS obtained by a self-organized Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE) process are of great interest since they offer an excellent cost-value ratio and are potentially easier applicable to non-flat substrates [7,8].…”

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

“…4 This passivation layer is not very stable and dissociates by heating or under the ion bombardment of the plasma. 9,10 Since our system is a remote plasma configuration, where 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, 17 the behavior of the etching rate as a function of O 2 content in the SF 6 /O 2 plasma, may be related to the fact that the passivation layer resists the degradation by plasma ions bombardment in the downstream etching region. Thus, this layer plays a significant role in the etching rate lowering beyond 5% O 2 content.…”

“…SF 6 /O 2 plasma mixture, providing the highly reactive etchant fluorine atoms, is widely used for silicon surface nanostructuring, [9][10][11][12][13][14] where the resulted Si nanostructures exhibited remarkable enhanced antireflective surface and light trapping efficiency, which is of great importance for photovoltaic applications to enhance the light absorption in Si solar cells. 10,11,13 The technological motivation behind our present work is to investigate, besides the light anti-reflection property, other potential applications of the Si nanostructures using the maskless SF 6 /O 2 plasma etching, such as light emitting (photoluminescence), photo-sensing (spectral response) and humidity sensing. In addition, this contribution will focus on the possibility of tuning these properties through varying the percentage of oxygen in SF 6 /O 2 plasma mixture, and on the relationship of different obtained properties to the etching rate, the surface morphology and the SiO x F y self-masking layer formation.…”

Wideband ‘black silicon’ for mid-infrared applications

“…All-silicon efficient narrowband and broadband absorbers have been studied recently [19][20][21]. In addition to these absorbers, needle-like black silicon structures emerged as interesting material with broadband absorbance of more than 99% [22,23]. Several methods are used to obtain black silicon including chemical etching, (deep) reactive ion etching, and laser treatment [24].…”