Etching Of Materials Research Articles

Surface science studies on electron-induced reactions of NH3 and their perspectives for enhancing nanofabrication processes

Ammonia (NH3) dissociates efficiently when it interacts with an electron beam. This applies not only to single electron-NH3 collisions in the gas phase but also to electron irradiation of NH3 adsorbed on surfaces. The dissociation products include atomic hydrogen which can act as a reducing agent or NH2 radicals that can bind to suitable surfaces or to adsorbed molecules. This chemistry can be exploited in nanofabrication processes that use electron beams for deposition, etching, or modification of materials. This review describes the current state of insight regarding electron-induced reactions of NH3 adsorbed on surfaces and outlines approaches to the use of these reactions for enhancing electron beam induced nanofabrication processes. First, an overview of surface science studies on electron-induced reactions of NH3 adsorbed on single crystal surfaces is given. This is followed by a summary of studies on the use of NH3 for improving the purity of deposits prepared by electron beam induced deposition (EBID) and on the prospects of NH3 to suppress unwanted thermal surface chemistry during EBID. Finally, we discuss electron-induced reactions of NH3 that are fundamental to the modification of carbonaceous nanomaterials as well as potential application scenarios such as the functionalization of self-assembled monolayers and humidity sensing.

(Invited) Selective Wet Etching of Semiconductor Materials by Novel Catalyst-assisted Modes

Since reports in the mid-1990s on metal-induced pitting on a Si surface in microelectronics, much attention has been paid to the positive use of corrosion of a semiconductor surface loaded with a metallic catalyst in solutions, known as metal-assisted chemical etching. This paper describes two novel modes of catalyst-assisted etching. The first involves the formation of nano trenches along the atomic step edges of a Si(111) surface with the help of self-assembled metallic nanowires, enabling the separation of neighboring terraces. The second discusses the science and application of nanocarbon-assisted etching, free from noble metals, of a Ge surface in water.

Modeling and Optimization of Wet ALE Process

Wet ALE (atomic layer etch) processes are emerging as an important alternative to standard ALE processes in semiconductor manufacturing. Here we present a model for simulating an idealized wet ALE process that includes both chemical reactions and liquid flow in order to predict the amount of material etch, how much of the etching is true ALE vs continuous etch, and its uniformity across the wafer. This model is applied to both a simple test flow cell and flow across a spinning wafer in a typical wet single wafer process. Results show that etch amount and uniformity depends on timing of the dispense steps, flow parameters, and the kinetics of the specific chemical reactions.

Modeling and experiment of femtosecond laser processing of micro-holes arrays in quartz

Quartz material irradiated by femtosecond laser has increasingly attracted widespread attention for the micro-fabrication of photonic devices. Mechanism exploration is beneficial for accelerating the digital progress of laser processing. However, the mechanism between femtosecond laser and quartz is complicated and needs further theoretical investigation. This paper established the theoretical model based on the ionization model with the Drude equation to study the space–time evolution of free electron density and its influence on the absorption coefficient, reflectivity, and ablation depth. In addition, we achieved a 10 × 10 micro-holes array with a pore size less than 10 μm, cone angle less than 2° in a 0.25 mm thick quartz on the condition of a laser pulse energy Ep = 3 μJ, scanning velocity v = 0.1 mm/s, and defocusing distance Δf = −0.3 mm via the bottom-up femtosecond laser processing. The work gives a new insight into further understanding the ablation mechanism of transparent materials etching by the femtosecond laser. It provides a practical technical scheme for preparing commercial quartz photonic devices.

PbS quantum dot thin film dry etching

Many consumer products used daily contain sensors and image sensors (smartphones, cars, automated tools, etc.). There is a growing demand to enhance the capabilities of industrial products to probe their environment more efficiently, i.e., under difficult conditions (smoke, darkness, etc.). One solution is to extend the capabilities of image sensors to detect light toward the near-infrared and short-wave infrared (SWIR) regions. Because silicon has weak absorption properties in the infrared, especially in the SWIR region, manufacturers are investigating the use of new materials to build these sensors. To this end, colloidal quantum dot (QD) thin films made from the assembly of PbS nanoparticles have emerged as promising materials. They offer tunable bandgaps, favorable absorption properties, and scalability in production. However, patterning the active parts of photodiodes by plasma etching of this new material presents challenges. The etching chemistry must be selected to volatilize Pb and S without modifying the unetched active part of the PbS QD photodiode, and the etching profile should be anisotropic. In this study, we have screened several plasma operating conditions (power, pressure, and temperature) in various chemistries (H2, Cl2, HBr, and N2). To understand the etch mechanisms and profiles, ToF-SIMS and TEM/energy dispersive x-ray were employed. Our findings reveal that halogen-based plasmas cause QD material deterioration through Cl or Br diffusion deep in the film. While H2 plasmas are efficient to etch PbS QD films, they result in high roughness due to the removal of the carbonated ligands that separate PbS QDs. This ligand etching is followed by QD coalescence leading to significant roughness. However, the addition of N2 to H2 can prevent this phenomenon by forming a diffusion barrier at the surface, resulting in favorable etching characteristics.

Nanoparticles synthesis in microwave plasmas: peculiarities and comprehensive insight

Low-pressure plasma processes are routinely used to grow, functionalize or etch materials, and thanks to some of its unique attributes, plasma has become a major player for some applications such as microelectronics. Plasma processes are however still at a research level when it comes to the synthesis and functionalization of nanoparticles. Yet plasma processes can offer a particularly suitable solution to produce nanoparticles having very peculiar features since they enable to: (i) reach particle with a variety of chemical compositions, (ii) tune the size and density of the particle cloud by acting on the transport dynamics of neutral or charged particles through a convenient setting of the thermal gradients or the electric field topology in the reactor chamber and (iii) manipulate nanoparticles and deposit them directly onto a substrate, or codeposit them along with a continuous film to produce nanocomposites or (iv) use them as a template to produce 1D materials. In this article, we present an experimental investigation of nanoparticles synthesis and dynamics in low-pressure microwave plasmas by combining time-resolved and in-situ laser extinction and scattering diagnostics, QCL absorption spectroscopy, mass spectrometry, optical emission spectroscopy and SEM along with a particle transport model. We showed for the first time the thermophoresis-driven dynamic of particle cloud in electrodless microwave plasmas. We showed that this effect is linked to particular fluctuations in the plasma composition and results in the formation of a void region in the bulk of the plasma surrounded by a particle cloud in the peripherical post-discharge. We also reveals and analyze the kinetics of precursor dissociation and molecular growth that result in the observed nanoparticle nucleation.

Plasma and Gas‐based Semiconductor Technologies for 2D Materials with Computational Simulation & Electronic Applications

AbstractThe technique of plasma processing is beneficial for wafer cleaning and precision etching of integrated circuits and essential in manufacture of advanced semiconductor devices with unmatched perfection. Research on two‐dimensional (2D) materials, such as transition metal dichalcogenides(TMDs), offers a promising solution to the challenges in semiconductor miniaturization. TMDs, with their atomic layer thicknesses and silicon‐like bandgaps, can be integrated using existing plasma systems. Different 2D crystal structures, such as 1T and 2H configurations, exhibit distinctive properties. Computational approaches are also developed to provide guidelines for controlled synthesis and etching of large‐scale and high‐quality 2D materials. Plasma/gas‐surface interactions during the synthesis, etching, and phase transformation of 2D materials are explored using atomistic simulations such as density functional theory and molecular dynamics. The reaction energetics, chemical species, and associated kinetics are discovered in the simulation study. These results decipher various mechanisms of 2D materials processing at the microscopic scale and predict certain optimal process parameters. Plasma/gas‐based semiconductor technologies are crucial in electronics because they enable production of advanced semiconductors. Plasma/gas etching allows precise and selective removal of material and plasma‐enhanced chemical vapor deposition enhances chemical reactions for efficient film deposition; therefore, these processes are majorly important for harnessing 2D materials in electronic applications.

Enhancing efficiency in photo chemical machining: a multivariate decision-making approach

Non-Traditional Machining (NTM) outperforms traditional processes by offering superior geometric and dimensional accuracy, along with a better surface finish. Photo Chemical Machining (PCM) represents one such NTM process, using chemical etching for material removal. PCM finds substantial application in the creation of microchannels in pharmaceutical, chemical and energy industries. Several input parameters—such as etchant concentration, etching time and etchant temperature—profoundly influence the machining’s quality and efficiency. Therefore, the optimization of these parameters is crucial. This study presents a comparative analysis of five Multiple Criteria Decision Making (MCDM) techniques—Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), Multi-Objective Optimization on the basis of Ratio Analysis (MOORA), Additive Ratio Assessment (ARAS), Weighted aggregated sum product assessment method (WASPAS) and Multi-Attributive Border Approximation Area Comparison Method (MABAC)—for the optimization of the PCM process. Key performance metrics considered are Material Removal Rate (MRR), Surface Roughness (SR), Undercut (Uc) and etch factor (EF). The weights of these criteria were calculated using the Criterion-Induced Aggregation Technique (CRITIC) and was compared with other popular methods like MEREC, Entropy and equal weights. MRR and EF are seen as beneficial criteria, while SR and Uc are perceived as cost criteria. Optimum process parameters were identified as 850 g/L etchant concentration, 40 min etching time and 70°C etchant temperature. Two of the three employed MCDM techniques agreed on these optimal parameters, reinforcing the findings. Furthermore, a strong correlation was observed amongst the employed MCDM techniques, further validating the results.

Plasma sheath tailoring by a magnetic field for three-dimensional plasma etching

Three-dimensional (3D) etching of materials by plasmas is an ultimate challenge in microstructuring applications. A method is proposed to reach a controllable 3D structure by using masks in front of the surface in a plasma etch reactor in combination with local magnetic fields to steer the incident ions in the plasma sheath region toward the surface to reach 3D directionality during etching and deposition. This effect has the potential to be controlled by modifying the magnetic field and/or plasma properties to adjust the relationship between sheath thickness and mask feature size. However, because the guiding length scale is the plasma sheath thickness, which for typical plasma densities is at least tens of micrometers or larger, controlled directional etching and deposition target the field of microstructuring, e.g., of solids for sensors, optics, or microfluidics. In this proof-of-concept study, it is shown that E→×B→ drifts tailor the local sheath expansion, thereby controlling the plasma density distribution and the transport when the plasma penetrates the mask during an RF cycle. This modified local plasma creates a 3D etch profile. This is shown experimentally as well as using 2d3v particle-in-cell/Monte Carlo collisions simulation.

Facilitated fluorination and etching of 2D materials

Precise control of functionalization and etching have been required for surface modification and device fabrication of two-dimensional (2D) materials. Specifically, fluorination of graphene has been used to control the properties of graphene. Recently, xenon difluoride (XeF2) has been used for selective fluorination of graphene and etching of other 2D materials, such as hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs). However, there is a lack of studies on key factors that govern the XeF2 treatment, which results in inconsistent behaviors of fluorination and etching. Here, we report control over chemical reactions between XeF2 and 2D materials using a chemical mediator of Si. Even a small amount of Si can accelerate the dissociation of XeF2, leading to the formation of chemically reactive xenon fluoride (XeF) that enhances the fluorination and etching of 2D materials. Additionally, our findings show that defects in 2D materials serve as chemically unstable sites that facilitate the additional dissociation of XeF2, generating F single atoms that easily form covalent bonds on the surface of 2D materials. Our study suggests that Si can be utilized as a reaction mediator to regulate XeF2 treatment on 2D materials, which has important implications for the fabrication of 2D electronic devices.

Modeling the impact of incomplete conformality during atomic layer processing

Atomic layer processing (ALP) is a modern fabrication technique for the deposition or etching of materials, which provides precise control of film thickness, composition, and conformality on a nanometer scale. This makes it crucial for the fabrication of high aspect ratio (HAR) structures, such as 3D NAND memory stacks, as its self-limiting nature provides enhanced conformality compared to traditional processes. However, as the number of NAND stacks grows and the aspect ratio continues to increase, deviations from full conformality can often occur due to precursor desorption from the surface. In this regard, a model for surface coverage during ALD in the presence of desorption, leading to incomplete conformality, has been developed and implemented in process simulation frameworks. This work is an extension of our previous research which concentrated on developing an accurate modeling approach for ALD in HAR structures (L.Aguinsky et al., Solid State Electron. 201, 2023). The model combines existing Knudsen diffusion and Langmuir kinetics methods and includes the Bosanquet formula for gas-phase diffusivity and reaction reversibility. It has been incorporated into academic and commercial level-set-based topography simulators. The parameters for the model have been calibrated using published results for the ALD of Al2O3 from trimethylaluminum (TMA) and H2O in HAR geometries. The temperature dependence of the H2O step is likewise analyzed, revealing an activation energy of 0.178eV, which is consistent with recent experiments. In the TMA step, the Bosanquet formula leads to improved accuracy, and the same parameter set is able to reproduce multiple experiments, demonstrating that the model parameters accurately capture reactor conditions. Finally, the developed model is combined with atomic layer etching (ALE) to simulate the controlled, conformal deposition of HfO2 inside HAR 3D NAND structures.

FEATURES OF CHEMICAL ETCHING OF TRACK STRUCTURES

Abstract. It is shown that computer simulation can be used to obtain important information about the mechanisms of etching of track structures. These data are necessary for the design and improvement of track biosensors. The etching process is simulated by appropriate modification of interatomic potentials. A new approach to studying the mechanisms of chemical etching of materials has been developed. A computer simulation method is used, which allows one to change the parameters of interatomic potentials in a certain mode during the simulation of the etching process. The main feature of the method is the creation of algorithms and new computer programs that make it possible to describe the coordinated change in the parameters of interatomic potentials (their “softening”), reproducing real chemical etching. The applied method for studying the mechanisms of chemical etching can be used in various technologies of electronic materials science. In the case of creating modern track biosensors, the use of appropriate chemical etching methods is especially important for improving these devices. This is due to the fact that the parameters of a track biosensor depend on the geometry of the track, its diameter, and the defective structure of the track walls. The study was carried out taking into account the three-layer structure of the track wall. Another option for using chemical etching is to study the defective structure of a material, in particular in the manufacture of biosensors, identifying the features of the threelayer structure of the track wall. The parameters of the biosensor depend on the nature of the interaction of particles of the “carrying” flow with the walls of the track. Therefore, it is important to ensure an optimal ratio of the mechanical characteristics of different defective layers forming the track wall. This is achieved by controlling the chemical etching process. In the future, the proposed method of computer modeling of the chemical etching process will be used in the study of dislocations and interfaces of multilayer and other materials.

An Alchemist of Super‐Cooled Liquid: The Art and Craft of Danny Lane

AbstractSculpting with glass is often the choice of artist and designer Danny Lane. He can combine it with steel, timber, acid etching and numerous other techniques and materials, yet at its root Lane's life's work is glass. He teases it to its limits for artistic effect – extruding, moulding, dripping, colouring, striating, cracking and nibbling at its edges. The other partner in his arsenal is light, the way it flickers, beams, glitters and projects. In an interview with AD Editor Neil Spiller, he reveals his thoughts on his creative history, his beloved material and his influences. Danny Lane, Etruscan Chair, 2016 This design for a glass and steel chair was originally conceived in 1986, and has been through various modifications since then; 1990s glass became 25mm thick and the metal was refined, with Jimmy Choo high‐heeled shoe tips.

Wet Cleaning/Etching of NiAl Thin Film

The effect of various chemical solutions and mixtures on the etch characteristics, roughness change, and surface composition of NiAl, Al, and Ni films were investigated. Both HCl solution (1.82%) and NH4OH (0.6 and 1.45%) solutions were found to have a detrimental effect on NiAl film in terms of material etching (4-point probe results) and surface roughness change (AFM). Within the concentration range applied, adding H2O2 into the HCl or NH4OH solutions resulted in a significant increase of the etching of the NiAl film. A correlation was observed between the magnitude of etching and increase in surface roughness suggesting that a preferential etching occurred, most likely of grain boundary. Experimental results showed that in the case of 1.82% HCl-H2O2 mixture, NiAl surface can be protected up to 240 s of immersion with the use of a corrosion inhibitor such as triazole (TA).

Plasma application in atomic layer etching

Atomic layer etching (ALE) has emerged as a promising technique for the precise and controlled removal of materials in nanoscale devices. ALE processes have gained significant attention due to their ability to achieve high material selectivity, etch uniformity, and atomic-scale resolution. This article provides a perspective of the important role of plasma in ALE including thermal ALE for nanometer-scale device manufacturing. Advantages as well as challenges of ALE are discussed in contrast to classic reactive ion etching. A tally-up of known plasma-based ALE processes is listed, and novel thermal ALE processes are described that are based on the so-called ligand addition mechanism. We explain the potential of using plasma for increasing wafer throughput in a manufacturing environment, its use when it comes to anisotropy tuning, the benefits in enabling a wider range of pre-cursors in thermal ALE, and the advantages it may bring for thermal ALE of crystalline materials. The benefits and challenges of different plasma sources in ALE are discussed, and an outlook for future development is provided. Finally, applications of plasma for productivity reasons such as particle avoidance and process stability are outlined.

Precise patterning of carbon films on polyethylene terephthalate polymer substrates using femtosecond lasers

A carbon film on a polyethylene terephthalate (PET) substrate is a novel type of flexible laminated material with unique mechanical and electrical properties, making it suitable for the fabrication of various flexible electronic components. However, due to its micron-level thickness, conventional mechanical processing methods are incapable of precisely removing the carbon film without damaging the substrate. Femtosecond laser processing is an advanced technique for achieving precise etching of thin-film materials due to its non-contact, high-precision, and minimal thermal effects. Therefore, we use femtosecond lasers to achieve precision etching of carbon resistive films on PET substrates to minimize substrate damage. In this study, a series of orthogonal and single-factor experiments were conducted to optimize the laser processing parameters. Various measurement and characterization methods, including X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, ultraviolet–visible spectroscopy, and confocal microscopy, were employed to analyze the removal of the carbon layer, changes in light transmittance, surface quality, and chemical composition of the processed substrate. Furthermore, the mechanisms of carbon film removal and PET substrate damage are explained.

Selective isotropic etching of SiO2 over Si3N4 using NF3/H2 remote plasma and methanol vapor

In this study, an isotropic etching process of SiO2 selective to Si3N4 using NF3/H2/methanol chemistry was investigated. HF was formed using a NF3/H2 remote plasma, and in order to remove the F radicals, which induces spontaneous etching of Si-base material, methanol was injected outside the plasma discharge region. Through this process, etch products were formed on the surface of SiO2, and then the (NH4)2SiF6 was removed by following heating process. When the H and F radicals were abundant, the highest SiO2 etch per cycle (EPC) was obtained. And, the increase of H2 and methanol percentage in the gas chemistry increased the etch selectivity by decreasing the F radicals. The etch products such as (NH4)2SiF6 were formed on the surfaces of SiO2 and Si3N4 during the reaction step and no noticeable spontaneous etching by formation of SiF4 was observed. By optimized conditions, the etch selectivity of SiO2 over Si3N4 and poly Si higher than 50 and 20, respectively, was obtained while having SiO2 EPC of ~ 13 nm/cycle. It is believed that the cyclic process using NF3/H2 remote plasma and methanol followed by heating can be applied to the selective isotropic SiO2 etching of next generation 3D device fabrication.

Comparison between Shear Strength in Total Etch and Self Etch Adhesive material in Bonding of Stainless-steel Brackets

Bracket bonding in tooth enamel with total-etch material is a general practice procedure. The researchers combine etchant and bonding procedures in one application or called self-etch. This procedure is a solution for timesaving in bonding procedures and minimizing enamel damage without degrading the ability to sustain bond strength during the application of an orthodontic appliance. The aim of this research is to know the comparison between shear strength, ARI value, and enamel crack length between total-etch and self-etch adhesive material. Eighteenth teeth are divided into three groups which are K-1 as a control group without etchant application, K2 as the self-etch material group, and K-3 as the total etch material group. All teeth practiced shear strength test by Universal Testing Machine Autograph. After bracket removal, an Adhesive Remnant Index (ARI) test was performed and followed by cleaning the adhesive remnant with tungsten carbide burs and continued by enamel crack test by Scanning Electron Microscope (SEM). According to the OneWay Anova result, there is a difference between shear strength, ARI value, and significant enamel crack length (p<0.05) between the control group, self-etch group, and total-etch group. Total etch material has higher shear strength, higher ARI value, and higher enamel crack length number than self-etch material.

Fabrication of 4H-SiC piezoresistive pressure sensor for high temperature using an integrated femtosecond laser-assisted plasma etching method

The processing, particularly, etching of brittle, hard, and anti-corrosion materials represented by the third-generation wide bandgap semiconductor silicon carbide (SiC), is a significant challenge. Although SiC has excellent electrical, mechanical, and chemical properties, the difficulty of processing limits its application in various sensor devices. To solve this problem, in this study, an integrated processing method of femtosecond laser-assisted SiC dry etching is proposed, which realizes high surface quality and high rate etching of the SiC microstructure. Specifically, the effects of different laser processing parameters on the processing effect were first studied through orthogonal experiments. Experiments indicate that compared with laser power and laser scan times, laser processing speed has a more obvious impact on the processing effect. Subsequently, considering the elastic modulus anisotropy of SiC, a 5 MPa piezoresistive pressure sensor chip was designed. Using the proposed composite processing method, a chip sensitive diaphragm was obtained. The diaphragm thickness and diameter are 76 μm and 1700 μm respectively. The overall sensor chip dimension was 4000 μm × 4000 μm × 350 μm. Static tests demonstrated that the sensor have excellent performance with sensitivity of 6.8 mV/MPa, linearity of 0.69% FS, and repeatability of 0.078% FS. In addition, by designing high-temperature packaging, the sensor achieved a pressure test at 400 °C. This study verifies the feasibility of the composite processing method, realizes the fabrication and measurement of high-temperature pressure sensors, and provides a reference for the micro-and nanostructure processing of various SiC sensors.

High coupling efficiency waveguide grating couplers on lithium niobate.

We propose and validate a new, to the best of our knowledge, approach for high coupling efficiency (CE) grating couplers (GCs) in the lithium niobate on insulator photonic integration platform. Enhanced CE is achieved by increasing the grating strength using a high refractive index polysilicon layer on the GC. Due to the high refractive index of the polysilicon layer, the light in the lithium niobate waveguide is pulled up to the grating region. The optical cavity formed in the vertical direction enhances the CE of the waveguide GC. With this novel structure, simulations predicted the CE to be -1.40 dB, while the experimentally measured CE was -2.20 dB with a 3-dB bandwidth of 81 nm from 1592 nm to 1673 nm. The high CE GC is achieved without using bottom metal reflectors or requiring the etching of the lithium niobate material.