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As a non-destructive and rapid technique, optical scatterometry has gained widespread use in the measurement of film thickness and optical constants. The recent advances in deep learning have presented new and powerful approaches to the resolution of inverse scattering problems. However, the application of deep-neural-network-assisted optical scatterometry for nanostructures still faces significant challenges, including poor stability, limited functionalities, and high equipment requirements. In this paper, a novel characterization method is proposed, which employs deep-neural-network-assisted ellipsometry to address these challenges. The method processes ellipsometric angles, which are measured by basic ellipsometers, as functional signals. A comprehensive model is developed to profile nano-gratings fabricated by diverse techniques, by incorporating rounded corners, residual layers, and optical constants into an existing model. The stability of the model is enhanced by implementing several measures, including multiple sets of initial values and azimuth-resolved measurements. A simple compensation algorithm is also introduced to improve accuracy without compromising efficiency. Experimental results demonstrate that the proposed method can rapidly and accurately characterize nano-gratings fabricated by various methods, with relative errors of both geometric and optical parameters well controlled under 5 %. Thus, the method holds great promise to serve as an alternative to conventional characterization techniques for in-situ measurement.

Diamond nanostructures can have exciting applications in electronics and thermal management, but their controlled fabrication can be challenging. Here, we present a top-down approach for the fabrication of diamond nanorod (DNR) clusters, via use of metal masks (Al, Ag, Au, and Cr) and reactive-ion etching (RIE). Prolonged RIE on Ag and Cr masks yields distinct etching profiles, and DNR clusters are selectively formed from Ag masks, with individual nanorods having dimensions of ∼100 nm diameter and ∼ 1.5 μm length. Detailed electron microscopy shows thin layer of amorphous carbon (a-C) around single crystalline DNR cores. Chemical analyses also show presence of oxygen on the surface of the DNRs. Fabrication of the DNR clusters with scalable top-down approach could lead to new nanodiamond-based applications. [Display omitted] • Our study presents a top-down approach for fabricating diamond nanorod (DNR) clusters. • We uncover responses of different metal masks (Al, Ag, Au, and Cr) to plasma etching, providing valuable insights for optimizing fabrication processes. • In-situ decomposition of bulk Ag into nanoparticles during reactive-ion etching (RIE), facilitates controlled DNR formation. • Through detailed microscopic analyses, we characterize the morphology and composition of DNR clusters. [ABSTRACT FROM AUTHOR]

Anti‐icing polyimide (PI) thin films are a promising anti‐icing technology for aircraft. A processing method combining reactive ion etching with cooling and plasma chemical vapour deposition is proposed to fabricate anti‐icing PI thin films with microcolumns (PI‐M). The anti‐icing performance of PI‐M was examined. The apparent contact angle (APCA) was 153° ± 1.4°, and the APCA hysteresis was 8.5° ± 0.5°. The calculated Weber number was high, and a droplet on PI‐M rebounded within 2.56 s, whereas rebounding occurred more slowly on a smooth PI surface (PI‐S). The freezing time of droplets on PI‐M was 70% longer than that on PI‐S. The average ice adhesion force on PI‐M was 42% smaller than that on PI‐S. Repeated measurements of the ice adhesion force on PI‐M demonstrated that it was stable (deviation: ±1 N). The APCA showed that PI‐M is superhydrophobic, which indicates that droplets on PI‐M were in the Cassie state. The droplet bouncing behaviour was explained in terms of horizontal force equilibrium at the interface. The anti‐icing mechanism of PI‐M was modelled using heterogeneous nucleation theory and a contact area model. The results explained the good anti‐icing performance and suggested that PI‐M may have excellent potential for anti‐icing applications. [ABSTRACT FROM AUTHOR]

Abstract Deep reactive-ion etching (DRIE) is commonly used for high aspect ratio silicon micromachining. However, scalloping, which is the result of the alternating Bosch process of DRIE, can cause many problems in the subsequent process and degrade device performance. In this work, we propose a simple and effective method to smoothen the scalloping of DRIE trenches. The proposed method utilizes sidewall dry etching by reactive-ion etching (RIE) based sulfur hexafluoride (SF6) plasmas, following the DRIE process. To investigate the effect of the etch parameter on the scallop smoothing effect, the radio frequency (RF) power and gas flow are controlled. After the RIE treatment, the scallop smoothing effects were evaluated by measuring the average scallop depth under each condition. The scallop depth was reduced by 91% after implementing the scallop smoothing technique using RIE. Thus, our smoothening method based on SF6 plasmas would provide broad availabilities and applicability in silicon micromachining with the simple low-temperature process.

Hypothesis: Recent advances in micro- and nanotechnology have led to possible design of functional micro/nanostructured surfaces with micro/nanotopography features that can exhibit low adhesion properties. An important example of such structures is superhydrophobic surface, which is extremely water repellent. In the present work, the effects of surface microtopography on the wetting of poly(dimethylsiloxane) (PDMS) rubber film with the goal of producing superhydrophobic surface are investigated. Methods: Micropillar arrays inspired by biological structures found in nature are produced on PDMS surface using a soft microlithography technique with different pitch/width ratios. To this end, the masters are fabricated using conventional microfabrication techniques and photolithography. Master designs tested are inverted pillar shape fabricated by anisotropic etching of silicon (reactive-ion etching, DRIE), a high aspect ratio master and a low aspect ratio photoresist master.Findings: Our fabricated pillars have nano-scale ripples that arise from the series of alternating, independent silicon etching and sidewall passivation steps used in the DRIE process. The elastomeric stamps are negative replicas of the masters and they are fabricated by PDMS. The stamps have a regular array of protruding features, in order to make a pattern transfer to the target substrate during m-contact printing. Several pitch/width ratios are configured to optimize the relationship between surface topography and wetting behavior of PDMS film using static water contact angle measurements. We have correlated these structures with PDMS rubber hydrophobicity and have also characterized the transition from the composite (Cassie-Baxter) to wetted (Wenzel) states for different types of surface structures. The surface topography-dependent contact angle of water underwent a transition from Cassie-Baxter to Wenzel states at pitch size ~60 mm.

The surface photovoltage (SPV) technique was used to study the surface and electrical properties of Mg-doped, p-type AlxGa1-xN (0.06

One of the major problems with the bone implant surfaces after surgery is the competition of host and bacterial cells to adhere to the implant surfaces. To keep the implants safe against implant-associated infections, the implant surface may be decorated with bactericidal nanostructures. Therefore, fabrication of nanostructures on biomaterials is of growing interest. Here, we systematically studied the effects of different processing parameters of inductively coupled plasma reactive ion etching (ICP RIE) on the Ti nanostructures. The resultant Ti surfaces were characterized by using scanning electron microscopy and contact angle measurements. The specimens etched using different chamber pressures were chosen for measurement of the mechanical properties using nanoindentation. The etched surfaces revealed various morphologies, from flat porous structures to relatively rough surfaces consisting of nanopillars with diameters between 26.4 ± 7.0 nm and 76.0 ± 24.4 nm and lengths between 0.5 ± 0.1 μm and 5.2 ± 0.3 μm. The wettability of the surfaces widely varied in the entire range of hydrophilicity. The structures obtained at higher chamber pressure showed enhanced mechanical properties. The bactericidal behavior of selected surfaces was assessed against Staphylococcus aureus and Escherichia coli bacteria while their cytocompatibility was evaluated with murine preosteoblasts. The findings indicated the potential of such ICP RIE Ti structures to incorporate both bactericidal and osteogenic activity, and pointed out that optimization of the process conditions is essential to maximize these biofunctionalities. [ABSTRACT FROM AUTHOR]

Abstract Lab based x-ray phase contrast imaging (XPCI) systems have historically focused on medical applications, but there is growing interest in material science applications for non-destructive analysis of low density materials. Extending this imaging technique to higher density materials or larger samples requires higher aspect ratio gratings, to allow the use of a higher energy x-ray source. In this work, we demonstrate the use of anisotropic silicon (Si) etching in potassium hydroxide (KOH), to achieve extremely high aspect ratio gratings. This method has been shown to be effective in fabricating deep, uniform gratings by taking advantage of the etch selectivity of differing crystalline planes of silicon. Our work has demonstrated a method for determining Si crystalline plane directions, specific to (110) Si wafers, enabling high alignment accuracy of the etch mask to these crystalline planes. [ABSTRACT FROM AUTHOR]

Abstract State of the art grating fabrication currently limits the maximum source energy that can be used in lab based x-ray phase contrast imaging (XPCI) systems. In order to move to higher source energies, and image high density materials or image through encapsulating barriers, new grating fabrication methods are needed. In this work we have analyzed a new modality for grating fabrication that involves precision alignment of etched gratings on both sides of a substrate, effectively doubling the thickness of the grating. We have achieved a front-to-backside feature alignment accuracy of 0.5 µm demonstrating a methodology that can be applied to any grating fabrication approach extending the attainable aspect ratios allowing higher energy lab based XPCI systems. [ABSTRACT FROM AUTHOR]

Abstract High quality gratings are among the key elements for successful imaging with X-ray grating interferometry. Grating fabrication, specifically of absorption gratings, with high aspect ratio and large area, is a great challenge from a microfabrication point of view. In this paper the fabrication of absorption gratings by seedless electroplating of gold in high aspect ratio silicon moulds that are fabricated by deep reactive ion etching (Bosch process) is presented. We report on our latest results and discuss the possibility of reducing the grating period down to 1.3 μ m. In addition, the quality of the gratings is assessed by performing visibility measurements and imaging various samples on a compact in house X-ray grating interferometer. [ABSTRACT FROM AUTHOR]

Abstract Silicon nanopillar (Si NP) arrays with the axial p-n junction were formed and investigated. A method to fabricate Si NP ordered arrays by means of electron beam lithography using the negative electron resist and reactive ion etching is presented. The effect of strong resonance light scattering – change of the color of separate Si NPs - was demonstrated. One or several minima were registered in the measured reflection spectra. Thereat, the position of reflection minimum was changed with a change in Si NP diameter. A shift of the minimum position towards the longer wavelength spectral region with an increase in Si NP diameter was observed. A shift of the position of minima to the shorter wavelength spectral region with a decrease in Si NP pitch in microarrays with the same Si NP diameter was observed. The quantitative divergence in the position of reflection minima in Si NPs with calculated dependencies for Mie resonances was found. High photosensitivity of Si NP arrays with axial p-n junction to visible and near IR light was discovered. So, these structures may be used for selective photonic sensors. Highlights • Si NP ordered arrays with axial p-n junction were fabricated. • Strong resonance light scattering causes changes of Si NP color. • Arrays with axial p-n junction are highly sensitive to visible and near IR light. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • c-Si wafers have been plasma textured by using RIE process operating with CF 4 /O 2 gaseous mixtures. • Surface textures have been produced at different etch durations, utilizing room temperature and high process pressure. • Optimized surface textures gave low optical reflection loss. • The small pyramid-like structures on Si substrates can be proposed for the preparation of highly efficient Si-HJT devices. Abstract Dry and maskless texturing process of mono-crystalline silicon wafers using CF 4 /O 2 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 (<5%). Furthermore, we clearly observe a slowing down of the etching rate starting from 5 min and in correspondence with the appearance of the sponge-like structure coupled with pores formation. Geometric parameters of morphological features, such as RMS and average inclination angle of the surface features, have been correlated with some specific texture functions such as angular distribution of scattered light Ps(θ) obtained by Angular Resolved Scattering (ARS) technique. Shape and slope of the texture features strongly determine the amount of forward scattered light and, as a consequence, the amount of reflectance decrease. Surface texture obtained after only 3 min of etch and characterized both by well distributed small normal pyramids and by high average inclination angle, proves to be more effective in giving reflection reduction respect to other surface textures characterized by inhomogeneously distributed large cavities. Finally, we can well suppose that this small pyramid-like texture on Si-substrates can be used for the preparation of highly efficient heterojunction-based solar cells (Si-HJT). [ABSTRACT FROM AUTHOR]

Highlights • Determination of silicon nanomechanical properties by instrumented nanoindentation • Top-down fabrication of silicon pillar structures by nanoimprint lithography • Precise control of inductively coupled plasma cryogenic reactive ion etching • Qualitative and quantitative analysis of indentation modulus and hardness on monocrystalline silicon with different crystal orientation • Comparison of elastic-plastic response of bulk and micro-structured silicon materials Abstract Nanomechanical properties of bulk and micro-pillared monocrystalline silicon are experimentally investigated using nanoscale depth-sensing indentation technique. Silicon pillar arrays with different crystal orientations, i.e., Si<100>, Si<110>, and Si<111>, are prepared by means of a top-down approach consisting of nanoimprint lithography and cryogenic dry etching. A three-sided Berkovich tip used during the experiments has provided highly resolved load-depth-curves and imprinted hardness impressions on the silicon materials. Depending on the aspect ratio of the pillars, the axial stiffness of the objects under measurement has to be considered. Corrected values of the elastic modulus are determined revealing direct nanomechanical comparison between silicon bulk and pillar structures. In summary, enhanced comprehension of elastic-plastic-response occurred within micro-structured silicon materials is shown, providing the potential to use silicon pillar arrays as fundamental material for accurate force measurements. [ABSTRACT FROM AUTHOR]

Abstract Carbon-based materials have attracted much attention in biological applications like interfacing electrodes with neurons and cell growth platforms due to their natural biocompatibility and tailorable material properties. Here we have fabricated sputtered carbon thin film electrodes for bioelectrical measurements. Reactive ion etching (RIE) recipes were optimized with Taguchi method to etch the close field unbalanced magnetron sputtered carbon thin film (nanocarbon, nC) consisting of nanoscale crystalline sp2-domains in amorphous sp3-bonded backbone. Plasma etching processes used gas mixtures of Ar/O 2 /SF 6 /CHF 3 for RIE and O 2 /SF 6 for ICP-RIE. The highest achieved etch rate for nanocarbon was ≫389 nm/min and best chromium etch mask selectivity was 135:1. Biocompatibility of the material was tested with rat neuronal cultures. Next, we fabricated multielectrode arrays (MEA) with carbon recording electrodes and metal wiring. Organotypic brain slices grown on the MEAs were viable and showed characteristic spontaneous electrical network activity. The results demonstrate that interactions with nanocarbon substrate support neuronal survival and maturation of functional neuronal networks. Thus the material can have wide applications in biomedical research. Graphical Abstract Highlights • Plasma etching optimization for nanocarbon thin film with Taguchi-method • Successful fabrication of multielectrode array from nanocarbon thin film • Nanocarbon thin film supports neuronal culturing with similar viability as glass. • Nanocarbon multielectrode array allowed electrophysiological recordings. • Use of carbon for bioelectrical sensing is an attractive alternative to metals. [ABSTRACT FROM AUTHOR]

Abstract Nanofluidic channels with a depth of ∼100 nm were developed as a leak element, where the fluidic channels were etched on silicon wafer by reactive ion etching and then enclosed by direct silicon bonding. Instead of the Torr-seal gluing method, a tight lamination between the chip and the vacuum flange was achieved using indium gasket sealing, eliminating the influence of Torr-seal outgassing. Two leak elements with different amount of parallel channels were fabricated and their values were characterized by the difference method. The results demonstrate that the conductance of the leak elements behave in reasonable agreement with their theoretically calculated conductance with relative errors of approximately 4.9% and 42.7%, respectively. The gas flow through these leak elements realizes molecular flow at pressures ranging from high vacuum up to 105 Pa for helium, argon, and nitrogen and can therefore be used as predictable leak elements for any gas. Highlights • Nanofluidic channels with a depth of ∼100 nm are developed as a leak element and enclosed by direct silicon bonding. • A new leak element is packaged with an indium gasket to eliminate the influence of Torr-seal outgassing. • The conductance of the two leak elements is measured based on difference method. • The gas flow through the leak element is molecular flow range up to 105 Pa for helium, argon, and nitrogen. [ABSTRACT FROM AUTHOR]

The fabrication process of a microparabolic reflector using isotropic xenon difluoride (XeF2) etching technique is presented and analysed through this work for developing infrared antenna-coupled detectors. Although many parametric studies described the behaviour of this process in the literature, the non-linearity of the process and its dramatic dependency on the pattern definition result in great difficulties when adopting the process for developing a particular structure. The main focus of this work is, therefore, to present a detailed etching analysis as dictated in the proposed design providing the proper etching recipe according to the proposed structure design and its associated masking pattern. Deep insights into the process have been highlighted suggesting the necessity of the process assessment in terms of evaluating the threedimensional etched volume rather than the etched depth. This will potentially solve the non-linearity behaviour and the pattern dependency problem. The optimum etching recipe yields approximately a total volume of 0.354 mm³ through the proper patterning mask. The resultant parabolic cavities have 75 and 13mm in their diameter and depth, respectively, as required for the proposed structure. The integration of a microparabolic reflector with such detectors will potentially enhance the specific detectivity of these detectors. [ABSTRACT FROM AUTHOR]

In this work, the authors report a cost-effective fabrication method for making gallium nitride (GaN) light emitting diode (LED) arrays using SF6 plasma in a conventional reactive-ion etching (RIE) system. The etch rates for GaN were investigated with different radio-frequency power and carrier substrates. The surface roughness due to the etching was also determined for the various recipes used. The optical intensity and the temperature change during operation of the fabricated LED's were investigated. The effect of post-fabrication annealing on enhancement in the electrical and optical properties of the LED's was investigated. [ABSTRACT FROM AUTHOR]

An approach for improving sidewall roughness of high-aspect-ratio trench is developed. This method relies on the aspect ratio dependent scalloping attenuation (ARDSA) effect in Bosch process, employs reactive ion etching (RIE) process to avoid the rippled sidewall at the top of the trench, while retains Bosch process with increasing trench depth. As both the RIE and Bosch processes are recognized production techniques, this method is easy to implement. Compared with standard Bosch process, the maximum root mean square (RMS) roughness of the sidewall is brought down from 15.1 nm to 6.89 nm. [ABSTRACT FROM AUTHOR]

Metal contacts on semiconductors devices are normally defined by lift-off process, because no well-defined etch processes exist for some rare metals. In this work, an RIE process for gold contacts is introduced which requires a high-density plasma, generated by electron cyclotron resonance. The proof is given by the residual-free etching without fence-generation and micromasking in the vicinity of the mask. [ABSTRACT FROM AUTHOR]

Side etching and scalloping are unwanted but unavoidable phenomenon occurring during fabrication process of micro electro-mechanical system devices with the deep reactive ion etching technology. This paper reports the influence of deep reactive ion etching fabrication errors on the geometrical dimension (as a comb finger shape, width of the suspension beam), electrostatic force and displacement of electrostatic linear comb-drive actuators. A number of deep reactive ion etching experiments were carried out in order to find out the optimal etching and passivation time, which allows to achieve vertical and smooth sidewall, as well as acceptable side etching value. Discussion and evaluation of deviation between the theoretically calculated and measured displacements of the electrostatic linear comb-drive actuator were also reported. [ABSTRACT FROM AUTHOR]

We propose a high-performance porous metal–insulator–metal-type capacitive humidity sensor based on a functional polymer mixed with TiO 2 microparticles subjected to inductively coupled plasma (ICP) and reactive-ion etching (RIE) treatments. The humidity sensor is composed of a porous top electrode, a TiO 2 -containing functional polymer humidity-sensitive layer subjected to two types of oxygen plasma treatment, a bottom electrode, and a glass substrate. The initial O 2 ICP dry-etching utilizes higher intensity plasma for deep etching in the inlet holes on the top electrode to increase the contact area and shorten the vapor absorption path, thereby yielding high sensitivity and low hysteresis. Further, the RIE treatment leads to roughening of the polymer etching surface and further improving the performance of the humidity sensor. The functional polymer mixed with TiO 2 microparticles exhibits excellent hysteresis over a wide humidity sensing range. The fabricated sensors are tested at various relative humidity (RH) values, achieving an ultra-low hysteresis of 0.64% RH at 60% RH, a high sensitivity of 1.24 pF/% RH, a fast response time of less than 25 s, good temperature dependence, and a stable capacitance value with a maximum error rate of 0.15% over 120 h of continuous testing. [ABSTRACT FROM AUTHOR]

Inductively coupled plasma reactive-ion etching (ICP-RIE) is first applied to decrease the thickness of a Si substrate for light-addressable potentiometric sensor (LAPS) characterization. A simple and reliable process flow with the self-aligned Al layer as a hard mask layer in ICP-RIE is used to fabricate a thin semiconductor substrate with Al back-side contact. A single-side polished P-type Si wafer with a thickness of 350 μm is decreased to 100 μm by ICP-RIE from the polished side. The thickness of the thin Si substrate and the dimensions of the designed patterns determined by ICP-RIE are verified using scanning electron microscopy (SEM) and an optical microscope (OM). A selective high-dielectric constant insulator, niobium oxide (NbOx), is directly deposited on the unpolished side of the thin Si substrate as the sensing membrane of a LAPS by reactive ratio frequency (rf) sputtering. A high photocurrent was found in the ICP-RIE LAPS sample under back-side illumination, particularly in high-frequency operation. Compared to an Si substrate without ICP-RIE, 3-fold and 6.5-fold higher photocurrents were achieved by the proposed LAPS with ICP-RIE measured at 1 and 50 kHz of light modulated frequency, respectively. The highest modulated frequency of illumination was 50 kHz for an acceptable photocurrent in the LAPS with ICP-RIE, which is sufficient for two-dimensional (2D) images acquired with high-speed scanning. The NbOx layer deposited on the unpolished Si surface could automatically generate higher pH sensitivity than conventional polished Si surfaces because of the higher surface roughness. The calculated pH sensitivity and linearity were 55.8 mV/pH and 99.6%, respectively, in a pH range from 2 to 12. No clear degradation of hysteresis was found for the LAPS with ICP-RIE. For the designed patterns of the Al hard mask layer, the spatial resolution of the 2D image of the LAPS with ICP-RIE could be obtained by the difference between dimensions observed by OM and the dimensions calculated from the photocurrent versus scanning length controlled by the X-Y stage. A pattern with a length of 250 μm generated by ICP-RIE was measured as 255 μm in the LAPS with scanning step of 5 μm. ICP-RIE is demonstrated to achieve a spatial resolution of 5 μm in the Si-based LAPS. Further reduction of the thickness of an Si substrate by ICP-RIE controlling and its ability to create a dynamic 2D image are suggested for future investigation in spatial resolution optimization. [ABSTRACT FROM AUTHOR]

A microfabricated separation column designed for ultimate use in a wearable gas chromatographic micro-analytical system (μGC) for analyzing mixtures of airborne volatile organic compounds (VOC) is described. The monolithic μcolumn chip measures 7.1 × 2.7 × 0.075 cm and contains a 6-m long, 250 × 140 μm deep-reactive-ion-etched Si channel with a Pyrex cap, wall-coated with a polydimethylsiloxane (PDMS) stationary phase. Along the channel are three serial 2-m long spiral segments, each with an independent integrated resistive heater and thermal isolation features etched in the substrate. By turning the segment heaters on and off at strategic points during a separation, significant energy savings could be realized relative to heating the entire chip simultaneously (i.e., globally), with no loss in chromatographic resolution. A classical lumped element model was used as the basis for simulations of energy consumption, and a published band trajectory model was used to estimate analyte residence times in each segment. Four simple mixtures of volatile organic chemicals were used to evaluate the models and assess the energy consumed for zone heating and global heating under isothermal and temperature-ramped conditions. Modeled reductions in the required energy per analysis using zone (vs. global) heating ranged from 14 to 31% among the cases considered, depending on the heating profile (i.e., isothermal or ramped), heating schedule, and the retention times of the analytes in the mixture. Modeled energy reductions tended to underestimate experimental reductions, but differed by <2% in all cases considered. This approach to μcolumn design and operation shows promise for extending battery life in wearable μGC instrumentation. [ABSTRACT FROM AUTHOR]

This review reports the progress on the recent development of manufacturing methods of nanochannels of bio-nanofluidic chips. Various manufacturing methods including reactive ion etching, high energy beam processing method, interference lithography, nanoimprinting, thin film deposition processing technology, hot embossing, stress release processing technology, molecular self-assembly processing technology, PDMS deformation processing and biofabrication of nanochannels are illustrated and discussed. The advantages and disadvantages of each manufacturing methods are expatiated. A variety of bio-nanofluidic chips fabricated with different manufacturing methods are also expounded and analyzed. This paper will provide a particularly convenient and valuable reference to those who intend to research the fabrication of bio-nanofluidic chips. [ABSTRACT FROM AUTHOR]

Although the mechanisms of deep reactive ion etching (DRIE) of silicon have been reported extensively, very little by comparison has been discussed concerning DRIE of germanium. By directly comparing silicon and germanium etching in a time multiplexed DRIE process, the authors extract significant differences in etch mechanisms from a design of experiment and discuss how these differences are relevant to the design and fabrication of silicon and germanium collimating channel array x-ray optics. The differences are illuminated by characteristics such as reactive ion etching (RIE)-lag, aspect ratio dependent etching, and sidewall passivation. Specifically, the authors demonstrate the more severe nature of RIE-lag in germanium, especially at aspect ratios exceeding 13:1. In addition, the differences in the profile evolution between silicon and germanium are shown to be a result of differences in sidewall passivation. There is also a correlation between the different sidewall passivation and the inherent lack of scalloping in the case of germanium DRIE. [ABSTRACT FROM AUTHOR]

Novel optically-rough and physically-flat transparent conductive oxides (TCO) substrates were developed by spin-coating Al doped Zn 1−x Mg x O (AZMO) transparent conductive thin film on roughened glass substrates treated by a reactive-ion etching (RIE) process, for enhancing the light-absorption in superstrate-type solar cells without deteriorating growth of photoactive layers. These substrates possess features of high transmittance, low surface roughness and strong light-scattering behavior. A surface morphology of randomly distributed irregular cones was formed on the Corning 7059 glass substrate through the overlapping of several lens-shaped cavities etched by the carbon tetrafluoride-oxygen plasma during the RIE process. This rough interface morphology not only has light-scattering ability, but also shows an antireflection effect at the interface between the AZMO and RIE etched glass substrate. One prototype with 40 cycles AZMO coating on a RIE etched substrate showed a root-mean-square surface roughness of 4.6 nm, a sheet resistance of 75.1 Ω/sq, and a haze ratio in transmission of 12.2% at the wavelength of 700 nm. These TCO substrates were applied to the front electrode of superstrate-type hydrogenated amorphous Si single junction solar cells. The solar cells exhibited a current gain of 11% and an efficiency gain of 14% as well as similar open-circuit voltage and fill factor with respect to the ones deposited on the AZMO coated flat glass substrate. These substrates would enable an efficient light management and the growth of high quality photoactive materials simultaneously for superstrate-type thin-film solar cells. [ABSTRACT FROM AUTHOR]

The critical dimension (CD) is highly influenced by the reactive ion etching (RIE) of silicon in the CMOS technology. The CD has to be well-controlled since it is one of the most important features related to process stability and product quality. However, the RIE process involves a lot of parameters which are highly confounded and entangled and thus it is very difficult to analyze the process. To study and extract the influences of these parameters in terms of CD variation, screening experiments are carried out to obtain the necessary factors to develop a CD-related model. An elaborated model, based on the selected parameters, is then built up via applying the design of experiments and response surface optimization. This model is validated to be capable of characterizing the process as well as predicting the CD. [ABSTRACT FROM AUTHOR]

A row-column addressable 128 x 128 InAs/GaSb type-II superlattice midwave infrared photodiode array of 8 µm square pixels with 2 µm interpixel separation is fabricated with SU-8 polymer isolation after reactive ion etching pixel delineation. The dark current of the mesa etched + SU-8 passivated 8 x 8 µm² pixel is found to be ~800 nA at an applied reverse bias voltage, V = 0.3 V. The photoresponse of the same 8 µm square pixel under 2 ns pulsed condition shows a peak responsivity of ~0.03 A/W at λ ~3.8 µm at a temporal width of ~6 ns. This enables integration of the photodiode array with a winner-takes-all read out circuit for high speed tracking applications. [ABSTRACT FROM AUTHOR]

We report our findings in developing a low-power etching recipe using a newly acquired reactive-ion etching (RIE) tool (RIE-10NR, Samco, Japan), with the aim of achieving smooth and vertical sidewalls in micropatterned silicon substrate. We used a combination of CF4, SF6, and O2 gases, which at low power (30 W) and low pressure (2 Pa) allowed for vertical silicon etching (aspect ratio ~2). We used photoresist and silicon oxide as the etching masks. As it is a continuous etching process, scalloping effects were not present, which is contrary to the process done with an inductively coupled plasma-based "Bosch" approach. We also show a successful use of these microstructures as master mold in soft-lithographic techniques for producing devices in elastomeric materials that have applications in mechanobiology. To the best of our knowledge, the recipe we present here has the lowest combination of power and pressure for etching silicon with vertical profile using a standard, parallel plates RIE tool. [ABSTRACT FROM AUTHOR]

The authors investigated the inductively coupled plasma reactive-ion etching (ICP-RIE) of β-Ga2O3 using different fluorine and chlorine-based plasmas. Sn-doped (-201) oriented β-Ga2O3 substrates were etched using SF6/Ar, CHF3/Ar, O2/Ar, BCl3/Ar, and Cl2/Ar based ICP-RIE. Appreciable etch rates were obtained only with chlorine and boron-trichloride based plasmas, and the authors performed a comprehensive study on the composition and temperature-dependence of ICP-RIE of β-Ga2O3 in BCl3/Cl2/Ar plasmas in a temperature range of 22 to 205 °C. In general, the etch rate decreased with increasing Cl2 content in BCl3/Cl2/Ar plasmas. A high etch rate of 144 nm/min with a smooth surface morphology was obtained in BCl3/Ar plasmas, compared to 19 nm/min in Cl2/Ar plasmas. The etching behavior of Ga2O3 shows more similarity to that of Al2O3 than to that of GaN. [ABSTRACT FROM AUTHOR]

Parylene-C (PC) is one of the most frequently used materials for flexible implantable electrode. Its interface with metal or other PC layer is critical in PC–metal-PC “sandwich” implantable neural electrodes in relation to their long-term reliability. In this study, we aim to develop a method to improve metal-PC and PC–PC adhesion in PC-based neural electrodes. “Nano-forest” structure, composed of nanopillar array is fabricated on the surface of bottom PC by oxygen reactive ion etching (RIE). The contribution of this layer of nano-structure to mechanical adhesion and sealing property are evaluated respectively. The results verify that for PC based “sandwich” electrode, not only the mechanical adhesion among three layers, but also the sealing ability between PC layers are significantly improved. [ABSTRACT FROM AUTHOR]

We focused on inductively coupled plasma and reactive ion etching (ICP-RIE) for etching GaN and tried to fabricate distinctive GaN structures under optimized chemical etching conditions. To determine the optimum chemical etching conditions, the flow rates of Ar and Cl2, ICP power, and chamber pressure were varied in the etching of c-plane GaN layers with stripe patterns. It was determined that the combination of Ar and Cl2 flow rates of 100 sccm, chamber pressure of 7 Pa, and ICP power of 800 W resulted in the most enhanced reaction, yielding distinctive GaN structures such as pillars with inverted mesa structures for c-plane GaN and a semipolar GaN layer with asymmetric inclined sidewalls. The selectivity and etching rate were also investigated. [ABSTRACT FROM AUTHOR]

The reactive gas cluster injection process is an etching method that uses a neutral cluster beam without plasma. Low-damage Si etching can be realized with this method because of the very low irradiation energy; the product is free of charge-up problems and vacuum UV light damage. The ClF3-Ar neutral cluster injection system for angled etching was constructed with a nozzle that was placed at 45° from the sample normal. The angled anisotropic Si etching is demonstrated with a high aspect ratio. The lever structure, which is often used in microelectromechanical systems (MEMSs), was fabricated by double-angled etching with reactive gas cluster injection. A simple fabrication process for the lever structure was achieved by double-angled etching with reactive gas cluster injection. These results show that various three-dimensional (3D) structures can be fabricated by repeated anisotropic etching with varying angles and directions. It is expected that the angled anisotropic etching process will enable the creation of unprecedented structures for use in MEMSs or photonic crystals. [ABSTRACT FROM AUTHOR]

Molecular structures at the surface and buried interface of an amorphous ultralow-k pSiCOH dielectric film were quantitatively characterized before and after reactive ion etching (RIE) and subsequent dielectric repair using sum frequency generation (SFG) vibrational spectroscopy and Auger electron spectroscopy. SFG results indicated that RIE treatment of the pSiCOH film resulted in a depletion of ~66% of the surface methyl groups and changed the orientation of surface methyl groups from ~47° to ~40°. After a dielectric recovery process that followed the RIE treatment, the surface molecular structure was dominated by methyl groups with an orientation of ~55° and the methyl surface coverage at the repaired surface was 271% relative to the pristine surface. Auger depth profiling indicated that the RIE treatment altered the top ~25 nm of the film and that the dielectric recovery treatment repaired the top ~9 nm of the film. Both SFG and Auger profiling results indicated that the buried SiCNH/pSiCOH interface was not affected by the RIE or the dielectric recovery process. Beyond characterizing low-k materials, the developed methodology is general and can be used to distinguish and characterize different molecular structures and elemental compositions at the surface, in the bulk, and at the buried interface of many different polymer or organic thin films. [ABSTRACT FROM AUTHOR]

This paper reports the deep reactive ion etching of femtosecond laser–machined high-aspect graphitic channels through diamond. To begin, two chemical vapor deposition-grown diamond plates, one single-crystal and the other polycrystalline, are processed using the bulk microstructural modification technique of femtosecond-pulsed laser machining. Multiple laser parameters are varied in processing the polycrystalline sample, including laser pulse frequency, pulse energy, and number of pulses per micron step size between the back and the front of the diamond, whereas a constrained set of parameters is used with the single-crystal sample. Over the range of parameters evaluated for the polycrystalline diamond, Raman analysis exhibits photoluminescence from defects created near the surface through the laser machining process, but little, if any, graphite-like features. However, a Raman signal from graphite-like material is observed on the surface of the graphitic channels for the single-crystal diamond, from which it is determined that greater diamond to graphite-like phase conversion is obtained with a larger number of pulses per translation step and with a higher laser pulse energy. Further, a larger number of pulses per step results in strong luminescence, observed during Raman investigation. Subsequent deep reactive ion etching of the samples reveals that the laser–machined channels etch considerably faster near the surface than the surrounding diamond, and that a high relative etch rate is obtained even when graphite-like features are absent from the Raman spectra. The highest relative etch rate of the single-crystal sample was 1.61 μm/min. [ABSTRACT FROM AUTHOR]

Microfluid cooling solution is one of the most effective techniques for thermal management of high heat fluxes. A jet-based Si microcooler with multiple drainage microtrenches (MDMTs) has been developed for microelectronic thermal management. Integrated with MDMT in hybrid microcooler, the negative cross-flow effect between nearby nozzles is eliminated, and thus fully developed jet impingement can be enabled for each nozzle. An inlet/outlet flow arrangement layer has been introduced to achieve uniform pressure distribution. The effects of three types of arrangement structures on the hydraulic and thermal performance of microcooler have been analyzed and compared. Two different thermal/fluid simulation models have been constructed for microcooler design. The test vehicle with the new nozzle/trench layer is fabricated using double-side deep reactive-ion etching process. Assembly of the stacked microcooler and Si thermal test chip is finished through two-steps optimized thermal compression bonding process. With 0.05-W pumping power for the microcooler, the heat dissipation of 260 W/cm2 has been demonstrated, and the chip temperature can be maintained under 51 °C. Excellent agreement has been obtained between experimental and simulation results. With the MDMT, enhanced-microjet array impinging has been achieved, and uniform chip temperature distribution is obtained. [ABSTRACT FROM PUBLISHER]

The authors investigated the field emission characteristics of printed carbon nanotubes (CNTs) on KOVAR substrates with micro- and nanosize line patterns. Microsized line patterns were fabricated using photolithography techniques followed by an inductive coupled plasma-reactive ion etching process, and laser interference lithography techniques were used to fabricate uniform nanosized patterns over a relatively large area. CNTs were printed on the patterned substrate using a screen printing method. The field emission characteristics of each patterned substrate were compared to those of a nonpatterned substrate. Results revealed that varying the pattern size has an influence on the field emission characteristics. The reduction of the pattern size results in an increase in the total surface area. This surface patterning is found to provide additional areas for CNTs to adhere to the substrates, which, in turn, results in better adhesion of CNTs. As the size of the pattern is reduced, the field emission properties are improved. Specifically, substrates with nanosized patterns exhibited both the lowest turn-on field and the highest field enhancement factor (β). [ABSTRACT FROM AUTHOR]

Si-based solar cells with vertically aligned p-n junctions operating at high voltage were designed and fabricated. The plasma treatments and antireflection coating deposition on the working surfaces of both single- and multijunction cells were made using the special holders. It was shown that additional treatment of solar cells in argon plasma prior to hydrogen plasma treatment and deposition of diamond-like carbon antireflection films led to the improvement of the cell efficiency by up to 60%. Radio frequency waves support plasma generation and improve photoelectric conversion mainly due to reduction of internal stresses at the interfaces. Application of reactive ion etching technique removes the broken layer, reduces elastic strain in the wafer, decreases recombination of charge carriers in the bulk, and provides cell efficiency increase by up to ten times. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS) elastomer has emerged as one of the most frequently applied materials in microfluidics. However, precise and large-scale surface micromachining of PDMS remains challenging, limiting applications of PDMS for microfluidic structures with high-resolution features. Herein, surface patterning of PDMS was achieved using a simple yet effective method combining direct photolithography followed by reactive-ion etching (RIE). This method incorporated a unique step of using oxygen plasma to activate PDMS surfaces to a hydrophilic state, thereby enabling improved adhesion of photoresist on top of PDMS surfaces for subsequent photolithography. RIE was applied to transfer patterns from photoresist to underlying PDMS thin films. Systematic experiments were conducted in the present work to characterize PDMS etch rate and etch selectivity of PDMS to photoresist as a function of various RIE parameters, including pressure, RF power, and gas flow rate and composition. We further compared two common RIE systems with and without bias power and employed inductively coupled plasma and capacitively coupled plasma sources, respectively, in terms of their PDMS etching performances. The RIE-based PDMS surface micromachining technique is compatible with conventional Si-based surface and bulk micromachining techniques, thus opening promising opportunities for generating hybrid microfluidic devices with novel functionalities. [ABSTRACT FROM AUTHOR]

Conjugated polymer etching is a key step in the integration of electro-chemical devices into microsystems, and one of the most important challenges for this type of material is to achieve fast etching with commercially available equipment. Conjugated polymer electrochemical devices are promising as they are used in different devices such as OLED, sensors, supercapacitors and actuators. The recent emergence of conducting interpenetrating polymer network actuators (IPN) based on poly(3,4-ethylenedioxythiophene) (PEDOT) has allowed operation frequencies of over 1 kHz to be attained, thus pushing the limits of the conjugated polymer technology. The plasma dry etching step of these PEDOT-based active mechanical devices, with high etching rates of around 2 μm min −1 , enables the production of these electrochemomechanical devices. To understand the high etching rate of these materials a systematic study of the chemical degradation mechanism of each polymer has been carried on. From the analysis of the etching of all the polymer actuator components, a chemical self-degradation mechanism is proposed to explain the surprisingly high etching rate obtained for PEDOT based materials. Finally, to conclude this study, the usefulness of this fast etching is demonstrated with the operation of standalone micro-beam actuators. [ABSTRACT FROM AUTHOR]

The reactive-ion-etching (RIE) characteristics of phase change material GeTe in CHF3/O2 plasma for back end of nonvolatile phase change memory devices were investigated in this paper. The etch rate and surface root-mean-square (RMS) roughness of crystalline GeTe and amorphous GeTe films were studied with various etching parameters, such as gas mixture ratio, chamber gas pressure, and power. It is found that the etch rate first increases with the increasing concentration of O2 and get at peak value 68.5 nm/min at 12% O2/(CHF3+O2), then decreases from 12% to 20% of O2 fraction. The surface RMS roughness slightly increases with the increasing oxygen content. By changing the gas pressure, the etch rate of GeTe films increases approximately linearly with increasing gas pressure up to 50 mTorr. In addition, the etch rate increases approximately linearly with increasing power below 400 W. The XPS spectra shows that some non-volatile GeFx, GeOx, TeFx, and TeOx by-products were left on the etched film surface. From these results of etched TiN films and GeTe films, the result of RIE with one step recipe shows the formation of under-cut on the profile of etched film. However, the result of RIE with two steps recipe shows better vertical characteristic and few residues were left on the profile of etched film. [ABSTRACT FROM AUTHOR]

A two-channel gas chromatography column and a single-channel column were made by deep reactive-ion etching technology. The two short columns were coated with different stationary phases, and then linked without a modulator. This is to aim at increasing the sample capacity and achieving a higher separation efficiency in complex environments. The results show that the capacity of the connected column is approximately 4 and 1.5 times larger than that of the single- and two-channel columns, respectively. The linked column was utilized to separate a six-component mixture, composed of three simulants of nerve and blister agents and three interfering vapors. The results demonstrate that the combined column has a remarkably higher separation efficiency than the individual columns, and an acceptable resolution is achieved although the total length of the linked column is only 1.5 m. [ABSTRACT FROM AUTHOR]

A nanoforest of black silicon was prepared using a method combining aluminum-induced crystallization (AIC) and reactive-ion etching (RIE). During the AIC period, a rough layer, incorporating AlSix intermetallics, was formed. This layer acted as an etch mask for the RIE step. X-ray photoelectron spectroscopic (XPS) measurements were performed to further analyze the formation of black silicon. Compared to Si 3 N 4 and polysilicon, the black silicon exhibits a high degree of infrared absorption for wavelengths of about 3 to 5 μm and 8 to 14 μm, respectively. In addition, black platinum overlaid on the base of black silicon further improves the infrared absorption. This nanostructure forests of black silicon could be incorporated into the fabrication process for gas detectors, photovoltaic devices, and imaging applications to improve the infrared absorption characteristics. [ABSTRACT FROM AUTHOR]

Al mask combined with DRIE, which was etched by IBE and conventional RIE, were used to fabricate silicon micro-trench structures with high aspect ratio (HAR) for MEMS capacitors application. And the effects of IBE and RIE on mask and further on HAR structures are discussed. For Al mask, IBE produces smooth profile while RIE induces irregular breaches at the opening edge. For HAR structures, the sample affected by IBE shows less critical dimensional loss, lower sidewall roughness, and higher aspect ratio than that by RIE. Origin of these phenomena is that RIE is dominated by chemical reaction and aided by physical sputtering, and shows isotropy trendy, while IBE which is performed by pure physical sputtering exhibits anisotropy. In addition, etch rate shows a linear dependence on well-controlled process parameters and is uniform in IBE; in contrary, it shows coupling of uncertain variables and induces nonlinear performance in RIE. Consequently, the HAR trench structures with the average width of 5.98 μm, the aspect ratio of 24.4, and the verticality of 1.17 μm have been successfully fabricated by the synergetic effects of IBE and DRIE. [ABSTRACT FROM AUTHOR]

In this work, a silicon-based micro-probe array was fabricated using multi-step deep reactive ion etching (DRIE) and reactive ion etching (RIE) processes. The micro-probe structure was implemented using a micromachining technique through a combination of two anisotropic DRIE and two isotropic RIE processes with a single etch mask. The cone-shaped tip height and tapered tip-end angle were experimentally varied with respect to the first DRIE depth. As the first DRIE depth was decreased, the micro-probe tip height increased and the sharpness consequently improved. The conductive layer was exposed only at the tip ends of the micro-probe to form a conical ultra-micro electrode, and it was characterised via cyclic voltammetry measurements. [ABSTRACT FROM AUTHOR]

A facile one-step oxygen plasma irradiation in reactive ion etching (RIE) configuration is employed to nylon 6,6 fabrics with different mesh sizes to achieve surface nanostructures and improved wettability for textile and filtration applications. To observe the effects of power and irradiation time on the samples, the experiments were performed using constant irradiation time in varying power and using constant power in varying irradiation times. Results showed improved wettability after the plasma treatment. The FTIR spectra of all the treated samples exhibited decreased transmittance of the amide and carboxylic acid groups due to surface etching. The changes in the surface chemistry are supported by the SEM data wherein etching and surface nanostructures were observed for the plasma-treated samples. The etching of the surfaces is enhanced for higher power plasma treatments. The thermal analysis showed that the plasma treatment resulted in decreased crystallinity. Surface chemistry showed that the effects of the plasma treatment on the samples have no significant difference for all the mesh sizes. However, surface morphology showed that the sizes of the surface cracks are the same for all the mesh sizes but samples with larger mesh sizes exhibited enhanced etching as compared to the samples with smaller mesh sizes. Higher power induced higher negative DC self-bias voltage on the samples that favored anisotropic and aggressive etching. [ABSTRACT FROM AUTHOR]

A process based on the silicon-migration technology for the monolithic integration of micromechanical devices and complementary metal–oxide–semiconductor (CMOS) circuits is described. A cavity sealed with a silicon cover-diaphragm is first formed without the need of a sacrificial layer etch. The transistors are next fabricated. The issues of material and process incompatibility inherently present in many schemes of microsystem integration are largely avoided using this technique. The technology was demonstrated with the design, fabrication, and characterization of a $16 \times 16$ active-matrix tactile sensor integrated with a 16-stage CMOS ring counter for row scanning. [2014-0082] [ABSTRACT FROM AUTHOR]

We present microwave-frequency NbTiN resonators on silicon, systematically achieving internal quality factors above 1M in the quantum regime. We use two techniques to reduce losses associated with two-level systems: an additional substrate surface treatment prior to NbTiN deposition to optimize the metal-substrate interface and deep reactive-ion etching of the substrate to displace the substrate-vacuum interfaces away from high electric fields. The temperature and power dependence of resonator behavior indicate that two-level systems still contribute significantly to energy dissipation, suggesting that more interface optimization could further improve performance. [ABSTRACT FROM AUTHOR]

In this work, the thermal reactive ion etching (TRIE) technique for etching hard-to-etch materials is presented. The TRIE technique employs a self-heated cathode and a thermally insulated aluminum plate is placed on the cathode of a regular reactive ion etching (RIE) system. By optimizing the beam size to support the sample stage, the temperature of the stage can be increased to a desired temperature without a cathode heater. The technique was used to etch a bulk titanium plate. An etch rate of 0.6 µm/min and an etch selectivity to nickel of 100 were achieved with SF6 plasma. The proposed technique makes a regular RIE system a more powerful etcher without the use of chlorine gas, a cathode heater, and an inductively coupled plasma source. [ABSTRACT FROM AUTHOR]

Different etching rates subjected to the poly-Si/W gate-stacks of state-of-the-art inner-gate-recessed-channel-array-transistor under HBr/O2 plasma environment result in the asymmetrical SiBrx deposition on the sidewalls of the gate-stacks, causing both the fluctuation of the critical dimension (CD) and the degradation of electrical properties as a consequence. If a HF cleaning process either cannot completely remove SiBrx or was postponed for a certain period of time after finishing the reactive ion etching of the gate-stacks, asymmetrically deposited SiBrx residue unexpectedly reacted with air toform the oxidized etching residue such as SiOxBry. The growth of SiOxBry film on the sidewalls can eventually affect the gate CD and the overlap capacitance, resulting in the degradation of both saturation current and propagation time (tPD). A simple model for the diffusion of the SiBrx by-product during the asymmetrical etching process and the growth of SiOxBry film as a function of time delay is suggested. [ABSTRACT FROM AUTHOR]