Reactive Ion Etching Method Research Articles

Wide‐Range Wavelength Light Scattering from Black Silicon Layers: Profits for Perovskite/Si Tandem Solar Cells

This study investigates the optical properties (light reflectance, absorptance, transmittance, and scattering) of black silicon (b‐Si) layers formed using reactive ion etching method. The corresponding spectra are determined across the visible, near‐infrared, and near‐ultraviolet wavelength ranges (250–1400 nm). It is demonstrated that b‐Si layers reduce the reflectance, and increase the absorptance and light scattering due to the disordered distribution of the nanoneedles. Increasing the etching duration strengthens this trend. It is shown that b‐Si layers etched for 10 min can be considered perfect light scatterers upon reflection at wavelengths less than 700 nm. Based on the obtained results, the possible profits of light scattering from the b‐Si interlayer for perovskite/Si tandem solar cells are analyzed. It is substantiated that the b‐Si interlayer can increase the useful absorptance not only within the bottom Si solar subcell but also in the top perovskite solar subcell. The prospects for future research directions and challenges are also provided.

High-performance uncooled PbSe/CdSe nanostructured mid-infrared photodetector with tunable cutoff wavelength

Room-temperature (RT) high-performance mid-wavelength infrared (MWIR) Lead Selenide (PbSe)/Cadmium Selenide (CdSe) heterostructure nanocrystal photoconductors are designed and fabricated on commercial silicon dioxide on silicon (SiO2/Si) wafer via vapor phase deposition. Tunable absorption edges at 3.75 and 4.0 μm are demonstrated with different sizes of the nanostructure. The devices are annealed in oxygen to make the thin film much more sensitive to MWIR light. The detectors are etched by the reactive ion etching method to define an active area of 17.5 × 20 μm2. All devices exhibit external quantum efficiencies exceeding 100%, a clear indication of photoconductive gain. 1/f noise is the dominating noise source, and it follows Hooge's empirical relation for a homogeneous semiconductor. RT peak specific detectivity (D*) of 2.17 × 1010 and 1.61 × 1010 Jones is achieved for pixels with absorption edge at 3.75 and 4 μm, respectively.

Brushy C-Decorated BiTe-Based Thermoelectric Film for Efficient Photodetection and Photoimaging.

Current strategies for simultaneously achieving high thermoelectric performance and high light absorption efficiency still suffer from complex steps and high costs. Herein, two kinds of amorphous thermoelectric films of n-type Bi2Te3 and p-type Bi0.5Sb1.5Te3 with high Seebeck coefficients were prepared by pulsed laser deposition (PLD) technology. In addition, C-decorated films with excellent light absorption efficiency at the junction of the thermoelectric legs were prepared by simple drop coating and reactive ion etching (RIE) method. The TE/C-RIE composite device exhibits excellent photodetection performance under the conditions of simulated natural light, monochromatic light, and high-frequency chopping. The maximum responsivity and specific detectivity of the device can reach 153.58 mV W-1 and 6.97 × 106 cm Hz1/2 W-1 (under simulated natural light), respectively. This represents an improvement rate of 85.91% compared to that of the pure TE device. Benefiting from the excellent photodetection efficiency of the device and integration advantage of PLD technology, the composite structure can be expanded into integrated photoimaging devices. The accurate identification of patterned light sources with letters (T, J, and U) and digitals (0-9) was successfully realized by associating the response electrical signals of each electrode with the position coordinates. This work provides valuable guidance for the design and fabrication of wide-spectrum photodetectors and complex optical imaging devices.

Atomic Depth Image Transfer of Large-Area Optical Quartz Materials Based on Pulsed Ion Beam.

The high-efficiency preparation of large-area microstructures of optical materials and precision graphic etching technology is one of the most important application directions in the atomic and near-atomic-scale manufacturing industry. Traditional focused ion beam (FIB) and reactive ion etching (RIE) methods have limitations in precision and efficiency, hindering their application in automated mass production. The pulsed ion beam (PIB) method addresses these issues by enhancing ion beam deflection to achieve high-resolution material removal on a macro scale, which can reach the equivalent removal resolution of 6.4 × 10-4 nm. Experiments were conducted on a quartz sample (10 × 10 × 1 mm) with a specific pattern mask using the custom PIB processing device. The surface morphology, etching depth, and roughness were measured post-process. The results demonstrated that precise control over cumulative sputtering time yielded well-defined patterns with expected average etching depths and surface roughness. This confirms the PIB technique's potential for precise atomic depth image transfer and its suitability for industrial automation, offering a significant advancement in microfabrication technology.

Plasmonic Titanium Nitride Nanohole Arrays for Refractometric Sensing.

Group IVB metal nitrides have attracted great interest as alternative plasmonic materials. Among them, titanium nitride (TiN) stands out due to the ease of deposition and relative abundance of Ti compared to those of Zr and Hf metals. Even though they do not have Au or Ag-like plasmonic characteristics, they offer many advantages, from high mechanical stability to refractory behavior and complementary metal oxide semiconductor-compatible fabrication to tunable electrical/optical properties. In this study, we utilized reactive RF magnetron sputtering to deposit plasmonic TiN thin films. The flow rate and ratio of Ar/N2 and oxygen scavenging methods were optimized to improve the plasmonic performance of TiN thin films. The stoichiometry and structure of the TiN thin films were thoroughly investigated to assess the viability of the optimized operation procedures. To assess the plasmonic performance of TiN thin films, periodic nanohole arrays were perforated on TiN thin films by using electron beam lithography and reactive ion etching methods. The resulting TiN periodic nanohole array with varying periods was investigated by using a custom microspectroscopy setup for both reflection and transmission characteristics in various media to underline the efficacy of TiN for refractometric sensing.

Black Silicon: Breaking through the Everlasting Cost vs. Effectivity Trade-Off for SERS Substrates

Black silicon (bSi) is a highly absorptive material in the UV-vis and NIR spectral range. Photon trapping ability makes noble metal plated bSi attractive for fabrication of surface enhanced Raman spectroscopy (SERS) substrates. By using a cost-effective room temperature reactive ion etching method, we designed and fabricated the bSi surface profile, which provides the maximum Raman signal enhancement under NIR excitation when a nanometrically-thin gold layer is deposited. The proposed bSi substrates are reliable, uniform, low cost and effective for SERS-based detection of analytes, making these materials essential for medicine, forensics and environmental monitoring. Numerical simulation revealed that painting bSi with a defected gold layer resulted in an increase in the plasmonic hot spots, and a substantial increase in the absorption cross-section in the NIR range.

A study on the functionalisation of transparent anti-icing surface: A new approach

In this study, the author presented a novel approach to manufacture a transparent anti-icing surface through Deep reactive ion etching (DRIE) method on the glass substrate. Tested anti-icing parameters include: adhesive strength and freezing time on samples with different wettability, including as-received (untreated), superhydrophilic, hydrophilic, non-hydrophobic, and superhydrophobic. The results demonstrated the outstanding performance given by the superhydrophobic surface compared to the other samples, confirming the superiority of the non-wetting phenomenon and the important role of the surface treatment. In addition, by introducing a uniformed truncated structure that mimics the moth’s eye structure, the fabricated surface illustrated a significantly higher transmittance in the visible region compared to the as-received sample. This new study proposes a fast and highly applicable fabrication method for functional surfaces operating in harsh environments and outdoor optical applications.

A Thermal and Electro-Magnetic Hybrid MOEMS Microscanner With Integrated Spatial Light Modulation and Metalens for Resolution Enhancement of Infrared Imaging Systems

This article describes the development of a novel integrated thermal and electromagnetic hybrid microoptoelectro mechanical system (MOEMS)-based scanning actuator. Determining the optical architecture and components used for scanning are significant points of the study. A metalens and a coded mask, both of which can be produced by microfabrication methods, are used in the optical part of the actuator. In this context, a metalens consisting of nanoholes was designed and fabricated as the first alternative. Second, a specific coded mask was designed and applied to the center of the MOEMS structure for obtaining spatial light modulation. Captured scene images including the coded mask are processed and reconstructed by using the compressive sensing image processing algorithms. Silicon-on-insulator (SOI) is the substrate of structure and deep reactive ion and wet etching methods were used to fabricate the integrated actuator. To increase the optical transmission, the optically transmissive coded mask zone was coated with antireflective coating at the midwave infrared band. The magnetic field for obtaining Lorentz force on the actuators was achieved by using the neodymium permanent magnet located beneath the structure.

Transparency and icephobicity of moth eye-inspired tailored omniphobic surface

ABSTRACT In this work, we presented a facile method to introduce a transparent and anti-icing omniphobic surface fabricated on the glass substrate. The uniform moth eye-inspired structure was generated by the Deep Reactive Ion Etching method and followed by an additional wet etching step to enhance the sharpness of the nanostructure. A hydrophobe compound was assembled on the rough substrate by chemical vapor coating to achieve remarkable liquid-repellent properties. The tensile strength test was conducted using a designed apparatus to evaluate the anti-icing performance of functional surfaces compared to the as-received one. In addition, the optical performance in terms of transmittance and reflectance also was tested and revealed significant optical enhancement owing to the unique design of nanoarrays. The results demonstrated the great potential and proposed design for multifunctional surfaces.

High-Density Patterning of InGaZnO by CH4: a Comparative Study of RIE and Pulsed Plasma ALE.

InGaZnO (IGZO)-based thin-film transistors and selector diodes are increasingly investigated for a broad range of applications such as high-resolution displays, high-density memories, and high-speed computing. However, its potential to be a key material for next-generation devices is strongly contingent on developing patterning processes with minimal damage at nanoscale dimensions. IGZO can be etched using CH4-based plasma. Although the etched by-products are volatile, there remains a concern that passivation─an associated effect arising from the use of a hydrocarbon etchant─may inhibit the patterning process. However, there has been limited discussion on the CH4-based etching of IGZO and the subsequent patterning challenges arising with pitch scaling (<200 nm). In this work, we systematically investigate dry chemical etching schemes to pattern an IGZO film into densely packed nanostructures using CH4. Straight IGZO lines, ∼45 nm in width at a pitch of ∼135 nm, are produced by employing the traditional reactive ion etching method. While the passivating effect of CH4 does not impede the etching process, any further shrinkage of feature and pitch dimensions amplifies reactive ion etching-induced damage in the form of profile distortion and residue redeposition. We show that this is efficiently addressed via atomic layer etching (ALE) of IGZO with CH4 using a pulsed plasma. The unique combination of ALE and plasma pulsing enables controlled reduction of ion-assisted sputtering and redeposition of residues on the patterned IGZO features. This approach is highly scalable and is successfully applied here to achieve well-separated IGZO lines, with critical dimensions down to ∼20 nm at a dense pitch of ∼36 nm. These lines exhibit steep profiles (∼80°) and no undesirable change in IGZO composition post-patterning. Finally, ALE of IGZO under pulsed plasma, reproduced on 300 mm wafers, highlights its suitability in large-scale manufacturing for the intended applications.

Damage and residual layer analysis of reactive ion etching textured multi-crystalline silicon wafer for application to solar cells

As part of the surface texturing process of multi-crystalline silicon solar cells, isotropic etching is performed by using an acidic solution. Furthermore, metal catalyst chemical etching (MCCE), reactive ion etching (RIE), and laser etching are used to further decrease surface reflectance. This study aimed to increase the power conversion efficiency of the solar cell by improving the short-circuit current density (Jsc) using MCCE and RIE. During RIE, a byproduct and a plasma damage layer are formed on the silicon surface, which decrease the efficiency of the solar cell and therefore need to be identified and effectively removed. Transmission electron spectroscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses were performed to identify the byproducts formed during RIE to confirm that it was amorphous silicon oxide. Furthermore, an etching process using acidic and alkaline base solutions was used to remove the plasma damage layer and the Jsc loss was calculated using the reflectance. As a results, confirm a difference of up to ∼ 1.6 mA/cm2, and an improvement of approximately 0.6% was observed in the solar cell efficiency. These results show a method of minimizing Jsc loss and removing surface damage in a silicon solar cells fabricated using the RIE method.

Side edge emission from a waveguide substrate.

In this study, we fabricated embedded titanium dioxide (TiO2) nanograting structures with slanted cross section on a silicon dioxide (SiO2) substrate using electron beam lithography (EBL) and reactive ion etching (RIE) methods, and we analyzed their optical signals. The surface morphologies of the embedded TiO2 nanograting structures were monitored by a scanning optical microscope (SEM). By focusing the transverse electric (TE) polarized beam with the wavelength λ=633nm at the incident angle θ=22.0∘ from the rear side of TiO2 face, we could observe +1st and -2nd diffraction orders with diffraction efficiencies (I/Itotal): I1=23% and I2=19%, respectively, on a SiO2/TiO2 interface. Diffraction beams were waveguided to both left and right directions in a SiO2 substrate via total internal reflection (TIR); next, two guided beams were emitted from the side edges of the substrate. This work is expected to develop a highly efficient two-way waveguide optical interconnector.

Producing Silicon Carbide Micro and Nanostructures by Plasma‐Free Metal‐Assisted Chemical Etching

AbstractSilicon carbide (SiC) is a wide bandgap third‐generation semiconductor well suited for harsh environment power electronics, micro and nano electromechanical systems, and emerging quantum technology by serving as hosts for quantum states via defect centers. The chemical inertness of SiC limits viable etching techniques to plasma‐based reactive ion etching methods; however, these could have significant undesirable effects for electronic and photonic devices. This paper presents a plasma‐free, open‐circuit, photo‐induced metal‐assisted chemical etch for fabricating micro and nanoscale features without the inherent high energy ion‐related surface damage. The method presented herein utilizes above bandgap ultraviolet light, patterned noble metal (Pt), and a solution consisting of an oxidant potassium persulfate (K2S2O8) and an acid, hydrofluoric acid, to spatially define the etching morphology. The parameter space is comprehensively explored to demonstrate the controllability and versatility of this technique to produce ordered arrays of micro and nanoscale SiC structures with porous or solid sidewalls, and to elucidate the etching mechanism.

Optical properties of stepped-cone silicon nanostructures fabricated by nanosphere mask and RIE method

ABSTRACT Highly ordered silicon nanostructures were fabricated using the nanosphere mask and reactive ion etching method. A self-assembled SiO2 nanospheres monolayer obtained by spin-coating method was used as an etching mask for pattern transfer onto the Si substrate. The shape and height of these nanostructures were precisely controlled by the etching time. The optical properties of as-prepared nanostructure were investigated by experiments and simulation. Experimental results showed that the average reflectance in wavelength range of 400–1000 nm decreased from 33.6% to 4.6%. Simulation results were in good agreement with experimental results. Accordingly, this novel method is therefore considered to be an easy approach to fabricate different nanostructures for broadband antireflective surfaces for solar cells.

Gap-dependent SERS effect of ordered composite plasmonic nanoparticle arrays and its application for detection of sodium saccharin

Sodium saccharin (SS) is usually used in the field of synthetic sweeter food processing. Excessive consumption of SS may cause many health problems. Therefore, it is very necessary to achieve rapid and highly sensitive detection of SS. Here, method based on surface enhanced Raman scattering (SERS) effect using high density ordered gold wrapped polystyrene spheres ([email protected]) composite plasmonic nanoparticle arrays as substrate, can achieve quantitative detection of SS in aqueous solution within a certain concentration range. The gap distance between two adjacent [email protected] can be well controlled. Such arrays are fabricated by a magnetron sputtering deposition method on ordered separated PSs arrays manufactured through reactive ion etching (RIE) method. Due to the high density of sub-10 nm gaps contained in such arrays, the structure exhibits strong SERS activity. Finite difference time domain (FDTD) method calculation also confirms that the fabricated substrate possess enhanced electromagnetic field at the gap site. SERS measurement shows that the limit of detection (LoD) for SS is 10−7 M, which is far below the national standard (≤5 mg/kg ≈ 2.07 × 10−5 M). Further study shows a good linear relationship between SERS peak intensity and SS concentration in the range of 10−7 M～10−3 M. This study provides a new and highly sensitive SERS substrate for the simple, rapid, low cost and highly efficient detection of the SS.

Electron beam lithography inscribed varied-line-spacing and uniform integrated reflective plane grating fabricated through line-by-line method

A varied-line-spacing (VLS) and uniform integrated reflective plane grating was inscribed by electron beam lithography (EBL) and reactive ion etching method, and its displacement sensing characteristics was tested. For the VLS grating, the groove density was varied from 868 to 442 L/mm over the device, according to the designed linear density function, and the device was coated with an aluminized surface to reflect light. For the uniform grating, the groove density was 655 L/mm. A Y-type twin-core fiber with a collimator head was used to input light from a broadband source and collect reflected light from the integrated grating for analysis by an optical spectrum analyzer. The inscribed integrated grating length and width were 50 × 10 mm, and the input light angle was fixed at 23°.The integrated grating displacement characteristics was varied, when the light spot was irradiated at VLS and uniform grating simultaneously, with the result that as the light spot moved to different grating positions, two peaks of diffracted light were collected. For 0–35 mm displacement changes in 5 mm increments, for the VLS grating, the diffracted light wavelength changed from 945.3 to 1612.2 nm with sensitivity of 18.68 nm/mm, and linearity of 0.975; for the uniform grating, the wavelength shift was less than 3.2 nm.

Deep Reactive Ion Etching of Z-Cut Alpha Quartz for MEMS Resonant Devices Fabrication.

Quartz is widely used in microelectromechanical systems (MEMS). Especially, MEMS quartz resonators are applied to sensors and serve as sensitive elements. The capability of deep etching is a limitation for the application. Presented in this paper is a deep and high accuracy reactive ion etching method applied to a quartz resonator etching process with a Cr mask. In order to enhance the capability of deep etching and machining accuracy, three kinds of etching gas (C4F8/Ar, SF6/Ar and SF6/C4F8/Ar), bias power, inductively coupled plasma (ICP) power and chamber pressure were studied in an industrial reactive ion etching machine (GDE C200). Results indicated that the SF6/C4F8/Ar chemistry gas is the suitable and optimal choice. Experiment results indicate that Cr (chromium) mask can obtain a higher selectivity than aluminum and titanium mask. A “sandwich” structure composed of Al layer-Cr layer-Al layer-Cr layer was proposed. The Al (aluminum) film can play the role of releasing stress and protecting gold electrodes, which can enhance the thickness of metal mask. An optimized process using SF6/C4F8/Ar plasmas showed the quartz etching rate of 450 nm/min. Meanwhile, a microchannel with a depth of 75.4 µm is fabricated, and a nearly vertical sidewall profile, smooth surface is achieved.

A novel method to fabricate on-chip ultra-high-Q microtoroid resonators

Fabricating an optical microtoroid with ultra-high quality factor is an indispensable procedure both for scientific research and engineering. Here, HF/HNO3 wet etching is specially tailored to form silicon pillars for ultra-high quality factor microtoroids instead of xenon difluoride (XeF2) or reactive ion etching (RIE) methods. This is a low-cost, easily maintained and time-saving method. The method uses a very simple etching device and is robust to temperature variations and humidity changes at room temperature(20–25 °C). Anisotropy in isotropic HF/HNO3 etching, which may limit the quality factor, is minimized in the experiment. Quality factor dependence on silicon orientation is experimentally investigated and theoretically explained with group theory, which shows that [111] oriented silicon wafers are superior to [100] and [110] in the wet etching method. The maximum quality factor observed at 1550 nm waveband in the experiment is 1.05 × 108. We believe this technique will have great influence both on laboratory and future production use.

Rapidly Thinning Silicon Carbide By Anodization

SiC is a semiconductor material used to fabricate electronic devices that can operate under severe conditions, such as high temperatures, and which have some advantages over silicon-based devices (for example, high frequency and high power). The hardness of SiC is quite high (Mohs=9.5) and strong chemically inert, making it difficult be thinned. Up to now, since the majority carriers of n-type SiC are electrons, its application is more extensive, but it is also more difficult to thin. An effective etching method is by the reactive ion etching (RIE) method, which may produce satisfactory results in a smooth surface. In addition, according to reports, an efficiently etching processing can be performed by a high temperature (>700 C) molten alkali metal hydroxide (for example, NaOH). However, the equipment cost, operation convenience and thinning speed of these etching approaches are not as well as electrochemical etching, i.e., anodization. However, n-type SiC is very difficult to be anodized because of the lack of electric holes which are the key species for etching. In our report, we used a wafer bonding processing to form a temporary p-n junction by jointing to a p-type silicon, so that minority carriers, electric holes, in the mated p-type silicon can easily transfer to the SiC surface via a bias, resulting in a HF-based electrochemical etching. By the processing, the n-type SiC can be quickly thinned. After thinning, the p-type silicon subatrate can be easily removed without the chemical contamination on the thinned SiC substrate.Figure: The anodized surface of n-type SiC. Figure 1

Study of Nano Texturing on Multi-crystalline Silicon Solar Cells

Nano texturing has been confirmed as an effective structure to improve the efficiency of multi-crystalline silicon solar cells by reducing optical loss. In this study, nano textured solar cells are fabricated by the Reactive Ion Etching (RIE) method based on a conventional production line. Several characterization methods are employed to evaluate the morphology, minority carrier lifetime, quantum efficiency and electricity performance of both nano textured and micro textured solar cells. The results show that nano textured solar cell has the highest efficiency of 19.21 % and an average efficiency of 18.86%, which is 0.57 % higher than that of micro textured solar cells. Thus, the RIE method is an effective way to manufacture nano textured solar cells. It can demonstrably improve the photoelectric conversion efficiency of mass-produced solar cells and reduce the production cost, which is significant to the development of solar cell industry.