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During the fabrication of metal oxide semiconductor high electron mobility transistor based on AlGaN/GaN heterostructure, gate patterning is recognized as the most critical step that can lead to electrical degradation of the transistor. In this work, we performed the SiN cap layer plasma etching processes by two fluorine-based plasma processes (SF6/Ar and CHF3/CF4/Ar) with low (≈15 eV) and high (≈260 eV) ion energies. Moreover, we investigate the postetching treatment using a KOH solution in order to restore the quality of the AlGaN barrier surface after etching. The objective of this article is to evaluate the AlGaN barrier surface damage after the listed plasma etching processes and postetching strategies by using quasi- in situ angle-resolved x-ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscope. Accordingly, it is found that both high ion energy plasma processes lead to a significant stoichiometric change and modification of the AlGaN barrier layer into a 1.5 nm F-rich AlGaNFx subsurface reactive layer. The decrease in ionic energy leads to a decrease in the SiN etch rate and a significant improvement in the SiN/AlGaN etch selectivity (which becomes infinite) for both plasma chemistries. Moreover, the decrease in ion energy decreases the depth of the modification (about 0.5 nm) and reduces the stochiometric change of the AlGaN barrier layer. However, both low and high ion energy SF6/Ar plasma lead to 0.8 eV Fermi level shift toward the valence band. Furthermore, the KOH postetching treatment demonstrates complete and effective removal of the AlGaNFx subsurface reactive layer and restoration of the surface properties of the AlGaN layer. However, this removal leads to AlGaN recesses that are correlated to the thickness of the reactive layer formed during the etching.

International audience; Plasma etching techniques can result in damage and contamination of materials, which, if not removed, can interfere with further processing. Therefore, characterisation of the etched surface is necessary to understand the basic mechanisms involved in the etching process and enable process control and cleaning procedures to be developed. A detailed investigation by means of the combined use of scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM/EDS), X-ray photoelectron spectroscopy (XPS) and optical microscopy (OM) has been carried out on deep titanium trenches etched by plasma. This innovative approach has provided a further insight into the microchemical structure of the surface contamination layer on both the titanium and the nickel hard mask surfaces. The described experiments were conducted on 25 to 100-mu m wide trenches, first etched in bulk titanium by an optimised Cl-2/SF6/O-2-based inductively coupled plasma process, through an electroplated nickel hard mask. The results allow to identify chlorine, fluorine and carbon as the main contaminating agents of the nickel mask and to associate three oxidation states around the etched trenches highlighting certain specific aspects related to the passivation mechanism. These observations reinforce the scientific relevance of the combined use of complementary optical and imaging analytical techniques.

Pulse-modulated plasma etching of copper masked using SIO2 films was conducted via a CH3COOH/Ar. The etch characteristics were examined under pulse-modulated plasma. As the duty ratio of pulse decreased and the frequency of pulse increased, the etch selectivity and etch profile were improved. X-ray photoelectron spectroscopy and indicated that more copper oxides (Cu2O and CuO) and Cu(CH3COO)2 were formed using pulse-modulated plasma than those formed using continuous-wave (CW) plasma. As the concentration of CH3COOH gas in pulse-modulated plasma increased, the formation of these copper compounds increased, which improved the etch profiles. Optical emission spectroscopy confirmed that the active ingredients of the plasma increased with decreasing pulse duty ratio and increasing frequency. Therefore, the optimized pulsed plasma etching of copper via a CH3COOH/Ar gas provides better etch profile than that by CW plasma etching.

CHF3/Ar plasma was used to etch LiTaO3 crystal by inductively coupled plasmas technique. X-ray photoelectron spectroscopy was performed to investigate the etching mechanism. It was found that chemi...

Silicon oxycarbide (SiOC) film was etched using a CF4/C6F12O/O2 mixed gas plasma through an inductively coupled plasma etcher. Changes in the dielectric constant and surface chemical bonding properties were investigated using ellipsometry and Fourier transform infrared spectroscopy. Plasma diagnosis was carried out using a double Langmuir probe, ultraviolet detector, and residual gas analyzer. The physical and chemical plasma properties of CHF3 and C6F12O exhibited similar trends. However, the C6F12O mixed plasma exhibited a smaller change in dielectric constant compared to that of a conventional CHF3 mixed plasma, because of the lower ion density, ion energy flux, and UV intensity and thinner fluorocarbon-based polymer formation. Therefore, the liquefied C6F12O gas can substitute for the existing etching process gas and reduce the change in dielectric constant.

In this work, the surface modification using a two-steps plasma etching has been developed for enhancing energy conversion performance in polytetrafluoroethylene (PTFE) triboelectric nanogenerator (TENG). Enhancing surface area by a powerful O2 and Ar bipolar pulse plasma etching without the use of CF4 gas has been demonstrated for the first time. TENG with modified surface PTFE using a sequential two-step O2/Ar plasma has a superior power density of 9.9 Wm−2, which is almost thirty times higher than that of a pristine PTFE TENG. The synergistic combination of high surface area and charge trapping sites due to chemical bond defects achieved from the use of a sequential O2/Ar plasma gives rise to the intensified triboelectric charge density and the enhancement of power output of PTFE-based TENG. The effects of plasma species and plasma etching sequence on surface morphologies and surface chemical species were investigated by a field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The correlation of surface morphology, chemical structure, and TENG performance was elucidated. In addition, the applications of mechanical energy harvesting for lighting, charging capacitors, keyboard sensing and operating a portable calculator were demonstrated.

We present two different techniques for achieving low resistance ($, Comment: Accepted by Journal of Low Temperature Physics

We present a highly scalable, room-temperature strategy for fabricating vertical silicon nanotube arrays derived from a toroidal micelle pattern via a water vapor-induced block copolymer (BCP) self-assembly mechanism. A polystyrene-b-poly(ethylene oxide) (PS-b-PEO) BCP system can be self-assembled into toroidal micelle structures (diameter: 400-600 nm) on a PS-OH-modified substrate in a facile manner contrasting with other complex processes described in the literature. It was found that a minimum PS-b-PEO thickness of ∼86 nm is required for the toroidal self-assembly. Furthermore, a water vapor annealing treatment at room conditions (∼25 °C, 60 min) is shown to vastly enhance the ordering of micellar structures. A liquid-phase infiltration process was used to generate arrays of iron and nickel oxide nanorings. These oxide structures were used as templates for pattern transfer into the underlying silicon substrate via plasma etching, resulting in large-area 3D silicon nanotube arrays. The overall simplicity of this technique, as well as the wide potential versatility of the resulting metal structures, proves that such room-temperature synthesis routes are a viable pathway for complex nanostructure fabrication, with potential applicability in fields such as optics or catalysis.

Arrays of alternating metallic nanostructures present hybrid properties, which are useful for applications in photonics and catalysis. Block copolymer films provide versatile templates for fabricating periodic arrays of nanowires. Yet, creating arrays with alternating compositions or structures requires different modifications of domains of the same kind. By controlling the penetration depth of metal precursors into the film we were able to impregnate different layers of copolymer cylinders with different metals. Capitalizing on the hexagonal packing of the cylinders led to simultaneous formation of nanowires with alternating compositions and periodic arrangement on the substrate after plasma etching. Selective deposition of nanoparticles on the film enabled creating alternating bare and decorated nanowires, as well as trimetallic nanowire arrays.

A novel microwave plasma etching technique was used to reveal various types of dislocation on the C-face of 4H-SiC. Etch pits formed on the C-face of 4H-SiC by H2–O2 plasma etching were observed using a laser confocal microscope. Combining the sectional views and morphology of the etch pit, three types of threading dislocations were identified. For further verification, the Si-face was etched in molten KOH and compared with the C-face. In order to comprehend the mechanism of the microwave plasma etching of the C-face, an etching rate experiment was carried out. The etching rate exhibited Arrhenius-type temperature dependence and the activation energy was 29.5 kcal mol−1, indicating a surface reaction limited process. X-ray photoelectron spectroscopy was used to analyze the change in the chemical state of the C-face before and after plasma etching, so as to infer the chemical reaction that occurred during the etching process. This etching technique provides an affect method by which to investigate the propagation of dislocations in SiC crystals.

Plasma can be used to effectively remove coke from a metal surface. The plasma etching conditions of coke and emission spectrum characteristics on the metal surface in a complex structure can be determined in real-time using the flexible optical fiber of an emission spectrometer. In this study, the glow discharge hydrogen plasma etching characteristics of a graphite sheet covering Cu and Fe electrodes were investigated. Methane plasma and a bare Cu electrode without graphite were used to conduct experiments for comparison. The cathode was heavily etched owing to the chemical and physical reactions of abundant H and other active species. Many hydrocarbon particle shells with fuzzy boundaries of multilayer graphite were observed on the ground electrode as black dots with diameters less than 1 micron. The cracking reaction of etching process in the case of hydrogen plasma with graphite electrodes plays a leading role, but polymerization reaction is dominant for the methane plasma with bare Cu electrodes. Significant excitation peaks of the emission spectrum are observed in regions centered at 388 and 776 nm for the etching of carbon-rich electrodes in hydrogen-rich plasma. Different hydrocarbon and metal substrate bonds can exist even under strong etching conditions.

Polycrystalline silicon on silicon oxide (poly - Si/SiO x ) passivating contacts enable ultrahigh-efficiency interdigitated back contact silicon solar cells. To prevent shunt between n- and p-type-doped fingers, an insulating region is required between them. We evaluate the use of intrinsic poly - Si for this isolation region. Interdigitated fingers were formed by plasma deposition of doped hydrogenated amorphous silicon through mechanically aligned shadow masks on top of a full-area intrinsic hydrogenated amorphous silicon ( a -Si:H) layer. High-temperature annealing then crystallized the a- Si:H to poly - Si and drove in the dopants. Two mechanisms were identified which cause contamination of the intrinsic poly - Si gap during processing. During deposition of doped fingers, we show using secondary ion mass spectrometry and conductivity measurements that the intrinsic gap becomes contaminated by doped a- Si:H tails several nanometers thick to concentrations of ∼1020 cm−3. Another source of contamination occurs during high-temperature annealing, where dopants desorb from doped regions and readsorb onto intrinsic a- Si:H. Both pathways reduce the resistivity of the intrinsic gap from ∼105 to ∼10−1 Ω·cm. We show that plasma etching of the a- Si:H surface before crystallizing with a capping layer can eliminate the contamination of the intrinsic poly-Si, maintaining a resistivity of ∼105 Ω·cm. This demonstrates masked plasma deposition as a dopant patterning method for Si solar cells.

Oxygen plasma processis usually implemented for selective etching of organic films. The oxygen plasma etches the organic materials non-uniformly, the deep etching generatesthe rough surface morphol...

Fabrication of high aspect ratio microelectromechanical systems (MEMS) like comb drive structures are mostly done by DRIE (Deep Reactive Ion Etching) process. Bosch process is a type of DRIE which involves alternate repetition of plasma etching and side wall passivation to achieve deep vertical structures. A continued plasma etching may lead to tapered wall due to some lateral etching. Although, a straight and smooth wall is expected due to combined alternate processes of etching and passivation, very often the resulting walls are having surface undulations called as scalloping. So, due to slanting, scalloping and combined slanting and scalloping defects the working and performance of a MEMS device get affected. MEMS gyrocope is one such widely comercialized device, which is required to measure angular rotation wth certain accuracy. We take a simple single-axis MEMS vibratory gyroscope to study the effect on these defects on its dynamics performance. The study presented in the paper may be useful for including undesirable effects in designing MEMS vibratory gyroscopes.

The charging effect generated by the accumulation of negative charges on a mask surface strongly limits the perfect pattern transfer from the mask to the substrate during the plasma etching process, which leads to the deformation of etched features and severely damages the mask pattern. This study first verified that various placements of the holes will result in different distributions of the electric filed (E-field) and the etching rate. This work next shows that the electron angular distribution (EAD) is closely related to the damage to the mask pattern. Based on a reliable modeling framework, the effects of changing the EAD on the distributions of spatial E-field and the etching rate were examined focusing on two adjacent and asymmetrically-shaped mask holes. Specifically, both the E-field strength and the etching rate around the edge of the two mask holes can be greatly reduced by narrowing the EAD, meanwhile, the number of electrons penetrating into the bottom of two holes will be significantly increased. These results will reduce the mask pattern damage and improve the etching of high-aspect-ratio features into a substrate. In the cases of different EADs, the simulated evolution rates of these two mask holes and the E-field strength inside the holes verify these conclusions. The mechanism is discussed in detail. This work will greatly help to optimize the etching technique.

Simultaneous plasma etching of a proton-exchange membrane (PEM) and deposition of a cerium oxide layer during reactive magnetron sputtering leads to the formation of a pronounced fiber-like structure on its surface. The level of structural porosity can be adjusted by varying the working pressure during the process. A PEM treated this way can be subsequently coated with a thin layer of iridium, forming an anode-side catalyst-coated membrane (CCM) for applications in water electrolysis. Due to the significantly enlarged surface of the membrane, there is no necessity for any additional, potentially corroding, support nanoparticles to achieve efficient in-cell operation. Moreover, utilizing a rotatory frame-shaped substrate holder and a multitarget deposition apparatus, the sputter-etching process can be used in the preparation of a full anode/cathode thin-film CCM in a single vacuum entry. This structure yields remarkable performance characteristics in an electrolyzer cell, considering its low combined noble metal loading of just 220 μg cm−2. Using this completely dry process for CCM manufacturing may facilitate efficient large-scale future production.

To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin silicon carbide (SiC) wafers with a high removal rate by conventional mechanical processing because their hardness and brittleness cause cracks and chips during thinning. Therefore, the authors have attempted to thin SiC wafers using plasma chemical vaporization machining (PCVM), which is plasma etching using high-pressure plasma. PCVM has a high removal rate because of the high radical density in the high-pressure plasma, and it does not form a damaged layer on the processed surface because of the low ion energy. The authors have already achieved a very high removal rate of 15.6 μm/min by PCVM. However, many etch pits were generated on the wafer during PCVM in these high-speed machining conditions. Therefore, this study, using molten potassium hydroxide (KOH) etching, investigated the cause of such etch pits and found that they may stem from threading screw dislocation in the wafers. In addition, this research considered a process for reducing an etch pit size and succeeded in doing so by controlling wafer temperature.

In this study, the Gaussian mixture model (GMM) was modified and implemented to determine the real-time endpoint of SiO2 plasma etching using optical emission spectrum analysis. Optical emission spectroscopy (OES) signals were collected from the SiO2 plasma etching processes, and the modified GMM was applied to SiO2 etching with relative areas of 8.0, 4.0, and 1.0 %. Consequently, the sensitivity of OES signals was improved by ~5.5 times, and the sensitivity factor of the modified GMM was increased by approximately two times, compared with those of the modified K-means cluster analysis (another clustering technique). In addition, 60 peaks related to the reactants were selected out of 6144 signals to improve the sensitivity of the modified GMM with full-spectrum wavelengths. The modified GMM analysis using the 60 reactant-related peaks exhibited a higher sensitivity (~1.4 times) than that with 6144 full-spectrum OES signals. Thus, the modified GMM can be a suitable and effective clustering technique for etching endpoint detection.

In order to reduce the interconnect resistance and capacitance (RC) time delay of a semiconductor integrated circuit, a more porous dielectric material is used in recent interconnection for lower dielectric constant. However, it is difficult to use highly porous low-k dielectric materials at the narrow pitch because it is easily damaged during the plasma etching processes. In this study, as one of the plasma induced damage reduction methods in the etching of porous low-k dielectric, RF pulsed plasma methods have been investigated by using a dual frequency capacitively coupled plasma etching system. RF pulsed plasmas generated more polymerizing species and less UV compared to continuous wave plasmas and showed reduced damaged layer compared to the conventional continuous wave plasma etching. Porous SiCOH dielectric patterned with a TiN hard mask was etched using the RF pulsed plasmas and the results showed more anisotropic etching profiles with less sidewall damages, which was estimated by the thickness loss of sidewall low-k material after dipping into a diluted HF solution. Therefore, it is believed that the RF pulsed plasma etching process of ultra low-k dielectric materials can improve the RC time delay related to plasma damage for the next interconnect manufacturing technology.

The limits of occurrence and the morphology of martensite in Cu-Zn-Al alloys with 30 to 50 wt pct Zn and ≤ 1.5 wt pct Al have been investigated. In samples with concentration gradients, various conditions for the competition between martensitic and massive transformation have been observed. Microstructural details of martensite were obtained by combining vibration polishing, chemical or plasma etching and polarized light, backscattered electron channeling contrast or electron backscatter diffraction analysis. Depending on the cooling rate, martensite undergoes a morphological change from self-accommodating thin plates to lenticular shaped plates, which is documented for the first time in Cu-based alloys. The number of martensite twins in the investigated compositional range was found to be significantly smaller than that in commercial Cu-Zn-Al alloys that are used as shape memory alloys.

Superomniphobic surfaces that repel liquids of extremely low surface tension rely on carefully fabricated doubly re-entrant topographies, typically made by silicon deep reactive ion etching technology. However, previously published processes have depended on critically timed etching steps, which are difficult to downscale. We present a scalable process that eliminates the critically timed etching steps. It is based on the use of silicon-on-insulator wafers and a silicon oxide foot of the micropillar, which makes the isotropic silicon release step non-critical. The process allows easy downscaling of pillars from 20 $\mu \text{m}$ to 10 $\mu \text{m}$ and $5~\mu \text{m}$ . The downscaling increases the stability of the Cassie state. Based on the process, we are able to create superomniphobic surfaces that sustain perfluorohexane (FC-72), which has the lowest surface tension of the known liquids at room temperature ( $\gamma _{\text {lv}}=11.91$ mN/m at 20 °C), in the Cassie state at droplet diameters down to 200 micrometers. These are the smallest perfluorohexane droplets repelled to date. [2019-0207]

Methods of micro-profiling of 4H-SiC are described: formation of mesa structures with inclined walls (off-vertical wall inclination angle exceeding 45°) by reactive ion etching; etching of mesa structures with a flat bottom and inclined walls (off-vertical wall inclination angle being smaller than 45°) by ion-beam and reactive ion plasma etching. The application of etching methods in the fabrication technology of 4H-SiC-based mesa-epitaxial field-effect transistors with a Schottky gate is demonstrated.

The anisotropic nature of plasma etching is usually exploited to realize vertical nano -/micro-silicon structures by deep reactive ion etching. However, some applications require tilted instead of perpendicular profiles with respect to the substrate. Here, a controlled tilted etching is realized by introducing a set of metal electric field modulator(s), which modify the near sample surface potential. The ions from the plasma body are accelerated under the influence of the distorted electric field, and hit the silicon surface with a certain incident angle. A model is built with finite elements method, taking into account the geometry of the experiment and the chamber conditions during the etching process. The thickness and the inter-distance of Al slabs have been varied in a range of 0.5-3 mm and 10-25 mm, respectively. A tilt angle ranging from 0?degrees to 22.6?degrees has been measured and validates the simulation results, showing that a desired tilt profile can be achieved with a proper parameters tuning. Examples of 1D and 2D modulations are reported with linear and chessboard slanted gratings for X-ray imaging applications., Applied Surface Science, 588, ISSN:0169-4332, ISSN:1873-5584

Damage of the gate oxide induced by plasma processing, due to charge buildup on conductors in ohmic contact with the oxide, was studied by special test structures consisting of a small test capacitor connected to large charge collecting antennas on conducting layers. Effects of various plasma processing steps in a model complementary metal oxide semiconductor process on the gate oxide quality, as revealed by the charge to breakdown (Q bd ) measurements, after successive processing steps are reported. The most pronounced degradation of the oxide quality occurred at the metal-1 etch: ΔQ bd =-1.9 C/cm 2 or 360 pC/μm of exposed edge. About 220 pC/μm of the cumulative value is due to the metal-1 etching and 140 pC/μm is due to the partial photoresist ashing

The conductivity of single layer and bilayer graphene ribbons 0.5–4 μm in width fabricated by oxygen plasma etching is studied experimentally. The dependence of the electron concentration in graphene on the ribbon width is revealed. This effect is explained by the edge doping of graphene due to defects arranged in SiO2 near the ribbon edges. The method of the formation of abrupt p–n junctions in graphene and structures with a constant electron concentration gradient in the graphene plane with the help of edge doping is proposed.

The corrosion of ceramic chamber parts causes particles in plasma etching process, so that the production yield and the overall equipment effectiveness (OEE) at LSI mass production line are decreased. We have developed magnesium oxide (MgO)-based ceramics whose corrosion resistance in reactive plasma is higher than conventional ceramic materials. In this study, we have prepared a shower-head-type electrode by using MgO-based ceramics, and demonstrated that the number of particles generated from the electrode is much lower than that generated from a conventional electrode made from aluminium oxide. The MgO-based ceramics contributes to improvement of the production yield and the OEE.

We present an alternative route to enhance antibacterial activity of polymer matrix nanocomposites that incorporate biocidal nanomaterials, using open-air atmospheric pressure plasma etching. We applied He/O2 discharges to rapidly remove the upper organic layers of ZnO -PMMA nanocomposite coatings, thus increasing the surface concentration of ZnO. To quantify the ZnO concentration from SEM images on the surface of the nanocomposite material, we developed and employed a new nanometrology method based on local variances of pixel luminosities and found a rapid increase of surface fraction up to 30% for the first 2 min of plasma treatment. Plasma etching resulted in enhanced antibacterial activity against Gram-negative E. coli cells after 4 h incubation under dynamic conditions. The results revealed an almost exponential drop of bacterial concentration with ZnO surface fraction, thus confirming the direct correlation of antibacterial activity with the interfacial area of the biocidal nanomaterial.

The growth of epitaxial (111) NiO films on (0001) LiNbO3 substrates by reactive magnetron sputtering has been reported for the first time. X-ray diffraction analysis of the obtained films was carried out in combination with layer-by-layer plasma etching. It was shown that a low lattice mismatch allows one to obtain structurally perfect thin layers of NiO on LiNbO3 substrates. With increasing film thickness, the structural perfection of the film deteriorates due to the accumulation of dislocations due to ion bombardment during growth.

This article presents a complete plasma etching process to etch high aspect ratio patterns on III-V/Ge solar cell heterostructure with low damage for the fabrication of multijunction solar cells with a through cell via contact architecture. A SiCl4/H2 chemistry was studied with different hydrogen dilutions within the plasma (0%, up to 67%) and with different cathode temperatures (20∘C, up to 200∘C). This chemistry choice creates a SiClx-based inhibiting layer on the sidewalls that promotes anisotropic etching through the epitaxial heterostructure. The study suggests that a high hydrogen flow and a low temperature reduce the chemical reactions that create sidewall erosion. A high hydrogen flow appears to provide a hydrogen passivation of the non-radiative defects on the III-V heterostructure sidewall during the etching process. III-V/Ge triple junction solar cells with standard grid line and busbar front and back contacts have been fabricated and via-holes were plasma-etched through the active layers in order to investigate the impact of hydrogen passivation on the photovoltaic performance. The results demonstrate that the hydrogen passivation enables an open-circuit voltage increase that persists even after 5 months. This plasma process can also be used for the mesa etching step on multijunction solar cells with standard contacts. Thus, it could provide an appealing pathway to increase the conversion efficiency of state-of-the-art multijunction solar cells with standard contacts. To complete the etching process, a liner is used to protect the sidewall properties and a time-multiplexed Ge etching process is proposed to finalize the patterning and even open a pathway towards III-V/Ge plasma dicing.

SiC is commonly used in the field of high temperature, high frequency, high power and radiation-resistant semiconductor devices and ultraviolet photodetectors due to its excellent photoelectric characteristics. Plasma etching is one of the key processes in the fabrication of SiC devices. However, it is difficult to obtain a smooth and vertical etch profile due to the subtrench effect when the conventional inductively coupled plasma (ICP) is used to etch SiC with small-size patterns (such as 1 μm holes or trenches), thus affecting the subsequent process and device performance. To study microscale pattern etch of 4H–SiC, we used different mask and etch gas systems for ICP etching. The etch profile was characterized using SEM. When the chlorine gas was used, there was no subtrench but a very inclined angle between the SiC bottom and sidewalls, which is hard to improve. When we used photoresist (PR) mask–HBr system, sidewall deposition happened. SiO2 mask–HBr/Ar system could help to etch different angles but has a limitation angle of up to 80°. Compared to above systems, the etching profile was much more vertical when HBr/SF6/O2 was used. After many rounds of process debugging, we obtain a good etching profile with flat and vertical sidewalls, no subtrench in the bottom and no damage of the SiO2 mask. Our work shows a good way of microscale pattern SiC etching by ICP.

We present a study that shows the independent influence of abnormal ion trajectories in the etched hole profile on thick dielectrics used in micro-electro mechanical system (MEMS) fabrication under fluorocarbon plasma. Under fixed neutral and ion fluxes, a simple dielectric block located on the chuck electrode can control the plasma molding effect, thus creating non-symmetric incidence ion angles. Changes in nanoscale etching profiles with variations in the plasma molding effect were obtained to investigate the quantitative effects of abnormal incidence ion angles under fixed plasma conditions. We found no significant changes in abnormal etching behavior with variation in the size of the nanoscale hole. We believe that this approach will be an effective method to support quantitative data of predictive modeling for the better understanding of abnormal plasma etching behavior in nanoscale device fabrications.

Piezoelectric P(VDF-TrFE) micro-cantilevers and beams have been developed with a novel micro-electromechanical systems process very useful for low frequency vibration sensors and energy harvesters. The devices were designed and simulated using COMSOL Multiphysics simulation software to determine the resonant frequency, voltage and power output for various dimensions with length in the range 200 μm to 2000 μm, width in the range 100 μm to 400 μm and thickness 2.5 μm in all cases. Devices were fabricated on silicon wafers using a novel bulk micromachining process by suspending them using critical process steps which include: micromachining of silicon substrate from the backside using anisotropic wet etchant TMAH to define the device suspension regions with thin SiO2 diaphragm, and release of micro-cantilevers and beams by etching the SiO2 diaphragm from backside with CHF3/O2 based plasma etching. All the devices were fabricated with 2.5 μm P(VDF-TrFE) spin coated on SiO2. Laser Doppler Vibrometer was used to measure resonant frequency, voltage and power output of the devices which were operated in longitudinal mode with thermally evaporated Cr-Au interdigitated electrodes for power extraction. The experimental results obtained on fabricated devices for the first time using this process were in good agreement with those derived from simulation.

We investigate the action of ion flows from a plasma onto the surface of a flat conductor lying on an insulator, with width less than the plasma Debye length. The model allows study of the processing with a steady state or pulsed potential on the microwire. The shape of pulses has been synthesized to provide the most homogeneous distribution of the etching rate over the microwire surface.

This work investigated a two-step surface modification of polyamide meshes and nonwoven fabrics for oil/water separation and looked into the durability of such modified polyamide. The two-step modification included 1) pre-etching the polyamide surface using plasma treatment and 2) coating the pre-etched surface by eco-friendly polydopamine (PDA)/cellulose. The pre-etching increased the surface roughness, which further improved the underwater superoleophobicity of the coating. Therefore, the modified polyamide was able to separate various oil/water mixtures and showed a higher intrusion pressure than the original sample and the samples which were only etched or only coated. The grooves on the surface that resulted from the pre-etching prevented the coating from peeling off. In durability tests, after 6 repeated uses, the modified nonwoven sample lost its underwater oleophobicity due to severe oil fouling, coming to a complete failure in oil/water separation. After 19 cycles, the modified mesh was still able to separate a certain amount of oil/water but showed reduced intrusion pressure because of slight oil contamination. Filters with different structures, like meshes with one layer of pores and nonwoven fabrics with complex three dimensional pores, had different oil fouling levels that affected oil/water separation. The recoverability of filters from oil contamination should be considered for practical applications.

An inductively coupled C H 4 / H 2 plasma etching process for delineation of InAs/GaSb type-II superlattice pixels is presented. An optimised C H 4 / H 2 etch recipe without alternate O 2 plasma cleaning step showed an etch rate as high as 0.11 μm/min that results in smooth vertical sidewalls for the type-II superlattice pixel arrays with 10 μm pitch size and 2.4 μm deep trenches. At 70 K, the dark current density for the mesa etched + SU-8 polymer passivated type-II superlattice photodiodes was found to be 0.11 A/cm2 at an applied reverse bias voltage of 0.2 V. The activation energy of 13 meV obtained from the Arrhenius plot and a variable area diode array technique showed that the measured dark current is mainly attributed to bulk tunnelling current. This technique of mesa delineation for the type-II superlattice pixel arrays with small pitch size is a viable option in realising next-generation infrared focal plane arrays.

Flexible and portable supercapacitors have been intensively investigated due to their reliable energy storage performance and promising applications in wearable electronic devices. Owing to the unique pseudocapacitance property of conducting polymer and the high conductivity and stability of carbon nanotube film (CNTF), polypyrrole (PPy) was electrodeposited on He plasma etched carbon nanotube film (HCNTF) for electrodes of flexible supercapacitor with high performance. As demonstrated by Raman spectra and contact angle measurement, He plasma etching can produce amorphous carbon on the CNTF and advance the hydrophilicity of the CNTF, which promoted the electrodeposition of PPy onto the CNTFs and improved the adhesion between PPy and CNTF. All-solid-state supercapacitors were fabricated using the PPy/HCNTF electrodes and H3PO4/PVA electrolyte. Cyclic voltammetry tests showed that the capacitive performance of PPy/HCNTF is much higher than that of PPy/CNTF. The specific capacitance of the PPy/HCNTF supercapacitor determined by a galvanostatic charge-discharge method at 0.5 A g−1 is about 414 F g−1, which was maintained 92% after 5000 cycles, reflecting high cycle stability. Moreover, the PPy/HCNTF supercapacitor could remain 96% of the original capacitance when it was bent for 500 times surrounding a cylinder with a diameter of 1.5 cm, showing perfect flexibility and great potential for flexible energy storage devices.

In this study, the reaction of NF3 gas plasma with cobalt oxide (Co3O4) film grown on the Inconel base metal surface was investigated. Experimental results showed the plasma etching rate as high as 3.36 μm/min at 350 °C under 220 W of plasma power with negative 300 DC bias voltage. AES and XPS analyses revealed that reaction product is CoF2, demonstrating that the plasma processing is a fluorination reaction. Based on the linear kinetics law, the activation energy of the etching reaction was derived to be 66.93 kJ/mol. This study demonstrates that the plasma decontamination technique can be applied to efficiently and effectively remove radioactive surface contaminants such as 60Co hiding in the oxide film on the surfaces of the metallic waste generated during decommissioning of old nuclear power plants.

Dry and maskless texturing process of mono-crystalline silicon wafers using CF4/O2 plasma in a reactive ion etching (RIE) system has been developed with the aim of obtaining optimized surface texture characterized by low optical reflection loss for photovoltaic applications. In this study c-Si has been successfully subjected to plasma etching at unusual process conditions, specifically high value of substrate temperature (15 °C) coupled with high value of process pressure (40 Pa). Different c-Si surface textures are produced at different etch durations. Specifically, pyramid-like morphology appears at very short etch time and crater-like nanostructures form at longer etch time, whereas the former gives the lowest average reflectance (

Transition metal nitrides (TMN) films, fabricated by physical vapor deposition (PVD), have attracted much attention in supercapacitor electrode applications due to their high conductivity, easily-controlled composition, high structural and chemical stability, and good cycling life, which are promising candidates for flexible thin-film supercapacitors and on-chip micro-supercapacitors. The main drawback of the PVD-TMN film electrodes is that they have relatively dense structure and smooth surface, which limits their specific surface area and capacitive performance of the supercapacitors. In this work, a novel strategy was employed to modify the surface morphology of TMN films by plasma etching technology. HfN films with high conductivity were chosen to be deposited by reactive DC magnetron sputtering, followed by plasma etching using Ar and Kr gases. Effects of plasma etching on the microstructure, surface morphology and electrochemical properties of the HfN films were investigated. The results indicated that plasma etching significantly changed the surface morphology and enhanced specific capacitance of the HfN films.

International audience; Micro-concentrator photovoltaic (CPV), incorporating micro-scale solar cells within concentrator photovoltaic modules, promises an inexpensive and highly efficient technology that can mitigate the drawbacks that impede standard CPV, such as resistive power losses. In this paper, we fabricate micro-scale multijunction solar cells designed for micro-CPV applications. A generic process flow, including plasma etching steps, was developed for the fabrication of complete InGaP/InGaAs/Ge microcells with rectangular, circular, and hexagonal active areas down to 0.089 mm 2 (0.068-mm 2 mesa). Large cells (>1 mm 2) demonstrate good electrical performance under one sun AM1.5D illumination, but a degradation in the open-circuit voltage (V OC) is observed on the smallest cells. This effect is attributed to perimeter recombination for which a passivation effect by the antireflective coating partially recovers the V OC. The V OC penalty for small cells is also reduced under high-intensity illumination, from 3.8% under sun to 1.0% at 974 suns. High intensity illumination yields an efficiency of 33.8% under 584 suns for a 0.25-mm 2 and microcells are expected to show higher efficiency than standard cells under very high concentration.

We report on the nanopatterning of horizontal and vertical germanium-tin (Ge1−x Sn x or GeSn) nanowires by inductively coupled plasma reactive ion etching for gate-all-around field effect transistors. First, a chlorine based chemistry has been investigated and optimal conditions identified for GeSn 6% alloys. Then, plasma etching was optimized to etch high Sn content GeSn alloys (up to 15%) with a high anisotropy, smooth sidewalls and a high selectivity versus a hydrogen silsesquioxane hard mask. We have shown that, in order to obtain smooth surfaces after plasma etching, a HCl pre-treatment was mandatory to eliminate the native Sn and Ge oxides. This behavior was even more pronounced for high Sn contents. Finally, we succeeded in patterning 20 nm wide suspended beams from GeSn layers with Sn concentrations up to 15%.

The cleaning of two-dimensional (2D) materials is an essential step in the fabrication of future devices, leveraging their unique physical, optical, and chemical properties. Part of these emerging 2D materials are transition metal dichalcogenides (TMDs). So far there is limited understanding of the cleaning of “monolayer” TMD materials. In this study, we report on the use of downstream H2 plasma to clean the surface of monolayer WS2 grown by MOCVD. We demonstrate that high-temperature processing is essential, allowing to maximize the removal rate of polymers and to mitigate damage caused to the WS2 in the form of sulfur vacancies. We show that low temperature in situ carbonyl sulfide (OCS) soak is an efficient way to resulfurize the material, besides high-temperature H2S annealing. The cleaning processes and mechanisms elucidated in this work are tested on back-gated field-effect transistors, confirming that transport properties of WS2 devices can be maintained by the combination of H2 plasma cleaning and OCS restoration. The low-damage plasma cleaning based on H2 and OCS is very reproducible, fast (completed in a few minutes) and uses a 300 mm industrial plasma etch system qualified for standard semiconductor pilot production. This process is, therefore, expected to enable the industrial scale-up of 2D-based devices, co-integrated with silicon technology.

Tantalum coatings have wide applications including as corrosion resistant coatings and radiopaque films for biomedical implants. However, producing coatings of sufficient thickness with the desired mechanical properties remains a substantial challenge. In this study, we show that the microstructure and properties of thick Ta films deposited on NiTi wires can be controlled significantly by pre-treating the substrate surface via ultrasonication followed by Aqua Regia etchant, or by plasma-based etching alone, while maintaining overall adhesive strength. Films from plasma and chemically etched samples exhibited substantially greater bulk texturing in the direction than the control film, also yielding more elongated and columnar grains. The extent of texturing in each sample was reflected in differences in Σ3 CSL boundary density. Additionally, only plasma etching yielded a β-Ta secondary phase. These microstructural observations demonstrate that film phase composition, texturing, grain shape distribution and grain boundary characteristics can be optimised for particular applications, simply by applying different NiTi substrate pretreatment regimes. It is suggested that this bears significant implications for influencing bulk properties such as cohesive and shear strength, as well as ductility, conductivity and cohesion in thick tantalum coatings.

Optical emission spectroscopy is informative and nondisturbing technique for diagnostics of various plasmas used for material treatment. In this work the distinctive features of emission spectra of NF3/Ar plasmas of various compositions formed during the plasma chemical etching of lithium niobate were studied. It was found that the wavelength region (220–290 nm) is of a particular interest for LiNbO3 etching control because it can be used to determine "endpoint" in multistep processes with sequencing of plasma etching and wet cleaning for LiF barrier layer removal. The influence of RF Inductively Coupled Plasma (ICP) power, total pressure, bias voltage, NF3 flow rate, and temperature of the susceptor was studied for five different ratios of NF3/Ar flow rates: NF3 (1.5 sccm)/Ar(9.2 sccm), NF3(7.0 sccm)/Ar(4.9 sccm), NF3(7.8 sccm)/Ar(10.8 sccm), NF3 (9.4 sccm)/Ar(3.3 sccm), NF3(11.7 sccm)/Ar(5.4 sccm). It has been shown that a decrease in total pressure and an increase in ICP power lead to an increase in the relative intensities of both argon and fluorine lines. At the same time the variations of bias voltage and susceptor temperature did not have a significant impact on spectral lines intensity of Ar and F. Optical actinometry technique was used to determine concentration of atomic fluorine in NF3/Ar plasmas at various process conditions to demonstrate a correlation between etching rate of LiNbO3 and fluorine atoms concentration.

Fluorine-containing polymers have attracted a lot of interest due to their hydrophobic nature, which enables a number of functionalities such as low friction, self-cleaning, anti-sticking, etc. Fluorinated ethylene propylene (FEP) is a copolymer of hexafluoropropylene and tetrafluoroethylene. In contrast to polytetrafluoroethylene (PTFE), FEP is melt-processable using injection molding and it is highly transparent and resistant to sunlight. Here, we transform fluorinated ethylene propylene (FEP) surfaces to superhydrophobic using plasma processing (i.e. plasma etching with simultaneous micro-nanotexturing followed by plasma deposition). Two different plasma reactors (an inductively coupled reactor and a reactive ion etcher) and different etching conditions are used in order to micro-nanotexture FEP surfaces. Superhydrophobicity is achieved after plasma deposition of a thin (30 nm) fluorocarbon coating. Subsequently, we probe their frictional properties against water drops using a tilting stage. In particular, we demonstrate wetting control of FEP surfaces with water static water contact angle ranging from 95o to 168o and hysteresis down to 1–2 o. Video analysis of drops moving on different FEP surfaces shows that water drops exhibit reduced friction as etching time increases so that a hierarchical morphology is created. This is achieved using both plasma reactors, whereas the optimum performance is observed for the 10 min etched surface in a inductively coupled plasma reactor in which friction force becomes 0.7–1 μN, which corresponds to an ultra-low dynamic coefficient of friction (at least one order of magnitude lower to that of untreated FEP).

Organic-inorganic lead halide perovskite materials have attracted wide attention owing to their great optoelectronic properties and low-temperature solution processability. Mesostructured perovskite solar cells (PSCs) could help to further improve the photovoltaic property. However, the existing approaches by inserting a layer of metal-oxide are generally need special treatment and consume much energy. In this work, an Ar plasma etching method is employed to modify composition of the perovskite absorb material with its morphology remain unchanged, which can effectively avoid unfavorable defects and enhance the charge separation efficiency. Based on controllable pore structure and porosity, the idiosyncratic mesostructured perovskite solar cells yield an 18.7% improvement in power conversion efficiency as compared with the common planar-type counterparts. Therefore, this method offers a room temperature scheme for high-performance mesostructured perovskite solar cells, making the flexible PSC possible.

Plasmonic silver nanoparticles (AgNPs) arranged on polyimide (PI) nanopillars (AgNP/PI) were developed as a stable photothermal surface-enhanced Raman spectroscopy (SERS) platform. The AgNP/PI substrates were prepared via maskless plasma etching and metal deposition using an in situ vacuum sputtering system. The AgNP/PI with high periodicity and high areal density led to high sensitivity, with a SERS enhancement factor (EF) of 2.2 × 108, and excellent reproducibility (relative standard deviation of 7.6%), as evaluated using the high-precision Raman mapping technique. To support the high SERS EF and sensitivity, the near-field enhancements of the dense AgNP array were calculated using a finite-difference time domain method. Notably, compared with AgNPs on polyethylene terephthalate (PET) nanopillar substrates, the AgNPs formed on the thermally stable PI nanopillar substrates exhibited excellent photothermal stability under illumination with a high-powered laser. The PI and PET surface changes induced by photoinduced local heating were investigated in terms of the glass-transition temperature, coefficient of thermal expansion, and thermal conductivity. The new plasmonic SERS platform has strong potential for reliable molecular detection in practical sensing applications with high-powered laser illuminations.

Black silicon (BSi or silicon micro/nanograss) is a frequently encountered phenomenon in highly directional etching of silicon using mainstream plasma etch tools. The appearance of BSi in most studies is considered to be caused by micromasks unintentionally present on the silicon surface that locally prevent silicon from etching. Particularly, under highly directional and selective plasma etch conditions, these chaotically arranged micromasks develop into tall grasslike structures that will absorb incoming light and make the etched silicon appear black. There are many different sources that might contribute to the formation of BSi. Most of them can be prevented by proper pretreatment of the surface and careful control of the etch parameters. However, the masking related to the in situ plasma passivation (typically FC- or O-species) and insufficient ion etching of this layer causing residues at horizontal surfaces remains a resilient issue that is difficult to control or predict. This study is built on a recently developed highly directional etch procedure called CORE (meaning Clear, Oxidize, Remove, and Etch) in which the usual FC inhibitor of the Bosch process is replaced by oxygen. Due to the self-limiting property of the oxidation step, the formation and controllability of BSi in the CORE sequence is different from how BSi presents itself in the FC-based sequences. In this work, the effects of different process parameters on the creation of masks and formation of BSi are carefully investigated. The authors show that the time in the removal (R) step of the passivating oxide layer in tight combination with the undercut time in the isotropic etch (E) step are the most important parameters to consider. By manipulating these two parameters and utilizing the self-limiting property of the oxidation (O) step, the CORE process can easily be modified to create either BSi-full or BSi-free surfaces independent of the aspect ratio of the etching features. The latter distinguishes the BSi formation clearly from other directional processes. The proposed CORE process thus provides the authors a versatile tool for creating BSi anywhere anytime or—as we call it—“BSi on Demand.”