Metal Etch Process Research Articles

An Improved Humidity Sensor with GO-Mn-Doped ZnO Nanocomposite and Dimensional Orchestration of Comb Electrode for Effective Bulk Manufacturing.

The measurement and control of humidity is a major challenge that affects the sensing properties of sensors used in high-precision equipment manufacturing industries. Graphene Oxide(GO)-based materials have been extensively explored in humidity sensing applications because of their high surface area and functional groups. However, there is a lack of effective bulk-manufacturing processes for the synthesis of 2D-based nanocomposites with comb electrodes. Moreover, water intercalation within the layers of 2D materials increases recovery time. This work demonstrates the enhanced sensing characteristics of a capacitive/resistive GO-MnZnO nanocomposite humidity sensor produced using a cost-effective single-pot synthesis process. The in-plane sensing layer consistently improves sensitivity and reduces response time for a wide range of relative humidity measurements (10% to 90%). Interdigitated gold electrodes with varying numbers of fingers and spacing were fabricated using photolithography on a Si/SiO₂ for a consistent sensor device platform. The choice of nanomaterials, dimension of the sensor, and fabrication method influence the performance of the humidity sensor in a controlled environment. GO nanocomposites show significant improvement in response time (82.67 times greater at 40% RH) and sensitivity (95.7 times more at 60% RH). The response time of 4.5 s and recovery time of 21 s was significantly better for a wider range of relative humidity compared to the reduced GO-sensing layer and ZnMnO. An optimized 6 mm × 3 mm dimension sensor with a 28-fingers comb was fabricated with a metal-etching process. This is one of the most effective methods for bulk manufacturing. The performance of the sensing layer is comparable to established sensing nanomaterials that are currently used in humidity sensors, and hence can be extended for optimal bulk manufacturing with minimum electrochemical treatments.

Patterning challenges for direct metal etch of ruthenium and molybdenum at 32 nm metal pitch and below

Ruthenium and molybdenum are candidate materials to replace Cu as the back-end-of-line interconnect metal for the tightest pitch features for future technology nodes. Due to their better figure of merit ρ0 × λ (ρ0 bulk resistivity, λ electron mean free path), it is expected that the resistance of <10 nm wide Ru and Mo metal lines can be significantly reduced compared to Cu. An important advantage for Ru and Mo is that both materials, in contrast to Cu, can be patterned by means of so-called direct metal etch, through reactive ion etching or atomic layer etching and can potentially be implemented without barrier. An integration scheme with direct metal etch instead of damascene patterning could simplify the overall patterning flow and eventually opens the possibility for exploring new integration concepts and patterning approaches. However, the learning on direct metal etch of Ru and Mo in the literature is scarce, especially at the relevant dimensions of today's interconnects. In this work, we will focus on the major patterning challenges we have encountered during the development of direct metal etch processes for Ru at 18 nm pitch and Mo gratings at 32 nm pitch. We have observed that the direct metal etch of Ru at these small dimensions is impacted by the growth of an oxidized layer on the sidewalls of the hard mask, which originates from the sputtering of the hard mask in combination with the O2-based Ru etch chemistry. This results in a narrowing of the trenches to be patterned and can easily lead to an etch stop in the smallest features. We will discuss several mitigation mechanisms to remove this oxidized layer, as well as to avoid the formation of such a layer. For patterning Mo with a Cl2/O2-based chemistry, the major patterning challenges we encountered are the insufficient sidewall passivation and the oxidation of the patterned Mo lines. The sidewall passivation issue has been overcome with an in situ thin SiO2-like deposition after partial Mo etch, while a possible mitigation mechanism for the Mo oxidation could be the in situ encapsulation immediately after Mo patterning.

Electrochemical performance of graphite/silicon/pitch anode composite prepared by metal etching process

Electrochemical performance of graphite/silicon/pitch anode composite prepared by metal etching process

Enhancement of Pool Boiling Heat Transfer over Plain and Rough Cylindrical Tubes

This study investigates the pool boiling heat transfer of water over cylindrical heating tubes for different orientations and surface roughness of the tubes. First, two orientations of a smooth heating tube, horizontal and vertical, were used in the boiling chamber. For a given heat flux, the heat transfer coefficient achieved with the horizontal tube was always higher than that for the vertical tube. To investigate the influence of surface roughness, a rough heating tube with a fully rough outer surface was developed through a metal etching process. Under the same range of wall superheat, the rough tube enhanced the heat transfer rate significantly compared to the smooth tube. Finally, a modified heating tube (MHT) was developed by axially roughening half of the surface of an originally smooth tube. The orientation angle of the rough surface of this MHT was varied from 0° (horizontal-upward) to 180° (horizontal-downward) in the chamber. The heat flux increased significantly with the increase of orientation angles from 0° to 90° (the maximum of 80 kW/m2 at 90°), whereas the same decreased as the orientation angle is further increased from 90° to 180°. Results revealed that the bubble dynamics over the heating tubes play a vital role in pool boiling performance.

High-resolution additive direct writing of metal micro/nanostructures by electrohydrodynamic jet printing

Patterned conductive structures have attracted significant attention as important components of printed and flexible micro/nanodevices. However, the fabrication of conductive micro/nanostructures with controlled and well-organized morphologies is a key challenge in the development and application of micro/nanoelectronic devices based on low-dimensional materials. To meet the requirements of depositing conductive structures on specific substrates, electrohydrodynamic jet (E-jet) printing, developed as a simple and effective method for fabricating micro/nanopatterns of polymers, was combined with a conventional wet metal etching process for patterning conductive metals on polymer substrates. Under optimized experimental conditions, we achieved fine straight-line patterns with a line spacing of 1 μm at a nanoscale printing resolution (average line width: 68 nm) and grid patterns with variable spacings and grid line widths, down to size of 871 nm. Furthermore, fully printed graphene photodetectors were obtained through in situ direct writing, and their photoelectric response to a change in photocurrent of 0.22 μA was demonstrated. The results suggest that combining E-jet printing with chemical etching is a promising mask-free approach for producing conductive metal patterns for micro/nanoelectronic devices.

Influence of Surface Treatment on the Interfacial and Mechanical Properties of Short S-Glass Fiber-Reinforced Dental Composites.

The influence of interfacial shear strength (IFSS) between processed short S-glass fibers (250 and 350 μm in length, 5 μm in diameter) and the dental resin (a mixture of urethane dimethacrylate and triethylene glycol dimethacrylate monomers) on the mechanical properties has been studied experimentally. The surface profile of short S-glass fibers was modified using a selective atomic level metal etching process and simple silanization process to enhance the interfacial properties. The S-glass fibers were etched in acid solutions to increase the surface roughness and selectively remove Al3+ and Mg2+ ions, which promoted the mechanical and chemical interfacial bonding reactions. The single glass fiber tensile and microdroplet pull-out tests were performed to investigate the effects of interfacial properties on the flexural strength of the resultant composites. The surface modified S-glass fibers showed an increase of 11-40% in IFSS compared to untreated glass fibers. Composites reinforced with 350 μm length glass fibers (AR-70), which were treated in piranha solution for 4 h, showed the highest improvement in overall mechanical properties, flexural strength (34.2%), modulus (9.7%), and breaking energy (51.9%), compared to the untreated fiber-reinforced composites. The modified Lewis-Nielsen equation was developed using the effective fiber length factor to accurately predict the modulus of the short fiber-reinforced composites and validated with experimental results.

A novel mask technology of glass HF etching and application in photovoltaic cells

In the process of glass etching, the design of mask and its preparation technology are very important, which directly relate to the quality of the process and the graphic structure of etching. Herein, to eliminate pinholes and minimize the side etching in the process of glass HF etching, a novel mask technology for glass deep etching was investigated. In order to compare the etching effect of glass, four different kinds of mask are prepared. They are Cu, or combinations of Cr and Cu with different thickness, respectively. The multilayer metal combination Cu/Cr/Cu/Cr with the thickness of them are 200 nm, 50 nm, 200 nm and 50 nm, is good to eliminate the pinholes and minimize the side etching, and it is proved theoretically by first principles calculation and stress simulation. This multilayer etching mask can be prepared by standard lithography and a metal etching process, and has been used successfully to fabricate light trapping regular pit arrays on the glass surface for photovoltaic cells, so this technology has broad application prospects in many fields of micro-electromechanical systems.

Application of PI-VM for management of the metal target plasma etching processes in OLED display manufacturing

Generation of the defect particles during the plasma-assisted metal dry etching process is induced by the various mechanisms. Most of these mechanisms are caused by the non-volatility of metal-halide compounds generated during the etching process. Degeneration of the metal etching process chamber condition is observed as the frequent process fault caused by the defects, but the worse condition is not recovered by itself. Because of this property of the metal etching process, proper work of the preventive maintenance (PM) to restore the process chamber or the addition of a discharge cleaning step is required periodically. However, inadequate PM or discharge cleaning by the uncertain cause analysis of the defect generation should be a just temporary remedy, and might lead the repetition of similar problems. To solve this problem, the virtual metrology (VM) model based on the plasma information (PI) parameters, known as PI-VM, was developed and applied for the defect control of the metal layer dry etching processes in organic light emitting diode (OLED) display manufacturing. To obtain the information about the generation rates of non-volatile compounds and their removal rates by the exhaustion system, PI parameters are designed with the consideration of the reaction kinetics in the metal etching plasma volume, sheath, and reacting surface using the big data of equipment engineering system (EES) and optical emission spectroscopy (OES) accumulated during the mass production process. The developed PI-VM index could be applied to a 2–3 h earlier alarm system for the defect occurrence, and had succeeded over 90% of alarm rate. This PI-VM alarm was applied to predictive control of the process by the early substitution of the discharge cleaning step or by the repair of the proper parts in the process chamber. By the control of processes based on the predicted results of the PI-VM, management of the mass production line with about 30% decreased defect was possible in OLED display manufacturing.

Enhancing the focused ion beam etch rate of Ag films by Joule heating

In this paper, the authors report on using Joule heating to increase the etch rate of focused ion beam (FIB) for etching Ag films. FIB is widely used as a tool for processing micro/nanomaterials. In this process, material atoms are expelled when the ion beam is irradiated on the material surface. On the other hand, Joule heating has been used for the structural modification of small-scale materials. Because in the FIB etching, the atoms are expected to be easily expelled by decreasing the density of grain boundaries of a metal, the FIB etch rate of the metal might be enhanced by structural modification with Joule heating. In this research, an Ag film was subjected to current-stressing, and FIB etching was carried out. It was confirmed that grains in the film grew due to Joule heating and that the FIB etch rate for Ag increased. The authors showed that the FIB etch rate for Ag could be enhanced by Joule heating. The results of this study will help in developing metal etch processes for micro/nanomaterials.

Higher‐order correlation–based multivariate statistical process monitoring

AbstractAs shallow architecture is inefficient in terms of computational elements, some incipient fault features can be characterized through the composition of many nonlinearities, ie, with deep network. In this paper, a novel approach is developed for multivariate statistical process monitoring based on higher‐order correlations. First, the correlations among monitoring variables can be learned by a multilayer learning framework hierarchically: The higher the number of layers to be stacked, the more nonlinear and abstract features can be characterized. Second, 3 monitoring statistics, SRE, M2, and C, are presented to monitor whether the process is remaining in control, and they are instructive for the identification of fault types. Moreover, only normal data are used in training phase; this can avoid the unbalance problem of different types of fault data. These capabilities of the proposed approach are illustrated with two industrial benchmarks, Tennessee Eastman process and Metal Etch process.

Simultaneous etching and transfer — Free multilayer graphene sheets derived from C60 thin films

Despite the advantage of chemical vapor deposition (CVD) for realization of large area epitaxial growth of graphene on transition metal catalysts, both etching and transfer process of CVD-grown graphene sheets still remain a big challenge. Here we demonstrate the formation of multilayer graphene (MLG) sheets tailored from C60 thin films on the top of Si/Ni substrate without etching and transfer steps based on Ni films. This self-assembled process separates the MLG sheets from the conductive Ni catalyst, embarking a possibility for direct characterizations of MLG sheets. The fine-tuned C60 films (30nm) are transformed into approximately 17 MLG sheets, thus making it large-area MLG sheets for a variety of direct applications.

Modeling micro-porous surfaces for secondary electron emission control to suppress multipactor

This work seeks to understand how the topography of a surface can be engineered to control secondary electron emission (SEE) for multipactor suppression. Two unique, semi-empirical models for the secondary electron yield (SEY) of a micro-porous surface are derived and compared. The first model is based on a two-dimensional (2D) pore geometry. The second model is based on a three-dimensional (3D) pore geometry. The SEY of both models is shown to depend on two categories of surface parameters: chemistry and topography. An important parameter in these models is the probability of electron emissions to escape the surface pores. This probability is shown by both models to depend exclusively on the aspect ratio of the pore (the ratio of the pore height to the pore diameter). The increased accuracy of the 3D model (compared to the 2D model) results in lower electron escape probabilities with the greatest reductions occurring for aspect ratios less than two. In order to validate these models, a variety of micro-porous gold surfaces were designed and fabricated using photolithography and electroplating processes. The use of an additive metal-deposition process (instead of the more commonly used subtractive metal-etch process) provided geometrically ideal pores which were necessary to accurately assess the 2D and 3D models. Comparison of the experimentally measured SEY data with model predictions from both the 2D and 3D models illustrates the improved accuracy of the 3D model. For a micro-porous gold surface consisting of pores with aspect ratios of two and a 50% pore density, the 3D model predicts that the maximum total SEY will be one. This provides optimal engineered surface design objectives to pursue for multipactor suppression using gold surfaces.

Thickness Control of Chemical Vapor Deposition-Grown Graphene Film by Oxygen Plasma Etching with Recycled Use of Ni Catalyst

Ni has been widely used as one of the most important metal catalysts for graphene growth with the chemical vapor deposition (CVD) method. Despite the many advantages, it is difficult to obtain high quality graphene from Ni due to the complexity in controlling the uniformity and thickness of multilayer graphene films. In this study, the thickness of multilayer graphene films grown on Ni was controlled by single-step oxygen plasma etching. The results show that the thickness of the graphene films proportionally decreased with an increase in the plasma etching time where the thickness was controlled from thick graphite films to thin graphene films with a transparency over 80%. Surface topology after oxygen plasma etching showed that uniform etching was achieved, for which the topmost surface of the resulting thin graphene is hydrophilic because of oxygen plasma irradiation, which is advantageous for coating organic layers in device fabrication. Moreover, because of the absence of a metal etching process, the recycled use of Ni catalysts is available, increasing the cost efficiency.

P‐211: Mechanism Analysis of SiOxNy Peeling on the OGS Organic Film Process

Comprehensive the above results, SiOxNy peeling on OC photoresist layer has a serious impact on the yield of products. This paper found that SiOxNy peeling reason is the process of acid attacking OC photoresist surface, which resulted in 200‐800Å expansion zone. The characterization confirmed that organic material was residue on OC photoresist expansion zone. The paper also shows organic substance was vaporized after high temperature and the dense SiOxNy film result in difficult to release gas, furthmore SiOxNy film bubble appearance. The experiment results show that by adding 230℃ anneal after Metal etching and Strip process, the Peeling can be solved which can improve the yield of the product.

Illumination intensity dependent photoresponse of ultra-thin ZnO/graphene/ZnO heterostructure

A heterostructure of zinc oxide (ZnO) and single layer graphene is fabricated by sandwiching a transferred graphene between two thin ZnO films (∼20 nm each). ZnO thin films were grown using decomposition of Zn(acac)2 and spin-coating technique. Graphene transfer route with PMMA temporary carrier and metal etching process was used to transfer high quality commercial graphene from copper foil on the zinc oxide surface on glass. This novel and ultra-thin heterostructure (∼40 nm) is sensitive for UV illumination and works as a photodetector (PD). In this device, both positive and negative photoconductivity (PC) were observed depends on illumination intensity and spectrum of incident light. Relatively long response and recovery times obtained in ZnO/G/ZnO structure are related to the metastable defect states of ZnO and its interfaces with graphene and/or silver contacts. The obtained results show that the transferred single layer graphene sheet between thin ZnO films could be a novel route for improvement properties this low-cost metal oxide.

Area-selective chemical vapor deposition of Co for Cu capping layer

Selective chemical vapor deposition (CVD) of Co on Cu interconnect lines is an advantageous method because it can simplify unit process and suppress side effects resulting from the metal etching process. Density functional theory calculations show that CoCp(CO)2 has a relatively higher kinetic barrier (36.2 kcal/mol) on SiO2 than that of Co2(CO)8 (22.9 kcal/mol). This indicates that CoCp(CO)2 could be a promising candidate as a Co precursor for selective CVD. Selective CVD of Co films is demonstrated experimentally by deposition on SiO2 and Cu substrates at 200 and 300 °C. To reduce C contents in the deposited film, a NH3 plasma process is adopted into conventional CVD in a cyclic CVD process. This process enables deposition of Co films with lower C content while maintaining selective deposition.

Magnetophoretic potential at the movement of cluster products of electrochemical reactions in an inhomogeneous magnetic field

An electric field arises from the influence of a nonuniform static magnetic field on charged colloid particles with magnetic susceptibility different from that of the surrounding liquid. It arises, for example, under the influence of a nonuniform static magnetic field in clusters of electrochemical reaction products created during metal etching, deposition, and corrosion processes without an external electric current passing through an electrolyte near a magnetized electrode surface. The corresponding potential consists of a Nernst potential of inhomogeneous distribution of concentration of colloid particles and a magnetophoretic potential (MPP). This potential has been calculated using a thermodynamic approach based on the equations of thermodynamics of nonequilibrium systems and the Onsager relations for a mass flow of correlated magnetic clusters under a gradient magnetic force in the electrolyte. The conditions under which the MPP contribution to the total electric potential may be significant are discussed with a reference to the example of a corroding spherical ferromagnetic steel electrode.

Effects of Fabrication Process Variation on Impedance of Neural Probe Microelectrodes

Effects of fabrication process variations on impedance of microelectrodes integrated on a neural probe were examined through equivalent circuit modeling and SPICE simulation. Process variation and the corresponding range were estimated based on experimental data. The modeling results illustrate that the process variation induced by metal etching process was the dominant factor in impedance variation. We also demonstrate that the effect of process variation is frequency dependent. Another process variation that was examined in this work was the thickness variation induced by deposition process. The modeling results indicate that the effect of thickness variation on impedance is negligible. This work provides a means to predict the variations in impedance values of microelectrodes on neural probe due to different process variations.

Self-assembly and nanosphere lithography for large-area plasmonic patterns on graphene

Plasmonic structures on graphene can tailor its optical properties, which is essential for sensing and optoelectronic applications, e.g. for the enhancement of photoresponsivity of graphene photodetectors. Control over their structural and, hence, spectral properties can be attained by using electron beam lithography, which is not a viable solution for the definition of patterns over large areas. For the fabrication of large-area plasmonic nanostructures, we propose to use self-assembled monolayers of nanospheres as a mask for metal evaporation and etching processes. An optimized approach based on self-assembly at air/water interface with a properly designed apparatus allows the attainment of monolayers of hexagonally closely packed patterns with high long-range order and large area coverage; special strategies are devised in order to protect graphene against damage resulting from surface treatment and further processing steps such as reactive ion etching, which could potentially impair graphene properties. Therefore we demonstrate that nanosphere lithography is a cost-effective solution to create plasmonic patterns on graphene.

Metal Etch in Advanced Immersion Tank with Precision Uniformity Using Agitation and Wafer Rotation

In semiconductor wafer fabrication, etching refers to the process of removing unwanted material from wafer surface through a subtractive process. Metal etching is most commonly used in the patterning of metal films for interconnects by establishing specific connection and conduction paths and can be classified by dry etching, de-plating and dissolution of the layers on various substrates such as silicon, SiO2, Si3N4, GaAs, germanium, and sapphire. Dry etching is used to produce very precise etching of vertical channels or vias forming the device features or lines which make up the conductive path because it is anisotropic or etching in one direction. Dry etching is achieved by using chemical gases and plasma in a process chamber so dry etching tools are very large, complex and expensive to purchase and operate. De-plating is a process of electro-chemically removing metal material from the surface of the wafer to an anode by creating a difference in electrical potential between the surface to be etched/de-plated (typically cathode) and the “target” or anode where the material is to be collected. De-plating in single wafer tools has also replaced immersion processing due to the better uniformity it provides. However, De-plating single wafer tools are also very large and expensive to operate and have low throughput (wafers per hour). Dissolution/Immersion is the used of recirculated chemical baths to perform the etching process. In an immersion bath chemical is used to dissolve the metal layer that is unprotected by the mask. Immersion metal etch process has been on the decline because of its isotropic etching property and poor etch uniformity caused by non-uniform chemical flow around wafers in the tank. For the most of etch processes lateral etching is undesired because it occurs on the walls of the features and makes them thinner or misshapen. As a result, most of critical etching steps are performed by dry etching systems. However, if etch uniformity is precise, immersion etching can be used for less critical features in place of complex dry etching and de-plating.