Etching Parameters Research Articles

Surface microtexturing design, laser-etching and adhesive failure of aluminum alloy single-lap-joint: Experiment and simulation

This study investigates the design and laser etching of surface microtextures on Al substrate to significantly improve the adhesive performance. Microstructures with different patterns were designed and fabricated. Also laser etching parameters such as etching power, line space and number of scans were thoroughly studied. The obtained microstructures exhibit excellent hydrophilicity, which is beneficial for the permeation of adhesives and formation of micromechanical interlocking. When testing the shear strength of the Al single-lap-joint, the results show great improvement compared with unetched specimens. In terms of the significance of laser parameters and textures on shear strength, power is the most significant, followed by number of scans, and finally line space and textures. The specimen designed with X-texture and etched by 20 W with scan space of 0.2 mm and number of 2 scans achieves the highest shear strength of 24 MPa and presents an improvement of 1225% in shear strength. In addition, multi-scale simulations were conducted to effectively demonstrate the interfacial bonding behavior and damage process of Al single-lap-joint. The proposed method shows great potential in improvement of bonding performance.

Role of etching parameters on the performance of porous silicon based photodetector devices

This work demonstrates the high speed porous silicon (P–Si) based photodetector with varying the etching parameters. The P–Si samples were fabricated using electrochemical etching. The microstructural characterization was performed using SEM, contact angle, FTIR and Raman spectroscopy. Further, these nanostructured samples were tested as photodetectors in the visible wavelength spectrum. The optimized sample based photodetector shows a higher photo to dark current ratio (PDCR) of 1.27 × 103 and less dark current as compared to the other tested photodetectors. Moreover, it also offers a higher detectivity of 5.97✕1011 Jones and rise/fall time of 0.017/0.010 s. The developed nanostructures and photodetectors are shown to have excellent process scalability and repeatability. These results demonstrate the potential applications of P–Si photodetectors for optoelectronic devices.

Weldability improvement of immiscible polycarbonate/GFRP by femtosecond laser surface treatment

Poor miscibility is an important reason for the non-weldable performance of most dissimilar polymers and their composites, and traditional surface treatments cannot effectively improve the weldability of dissimilar polymers. Therefore, the non-weldability of dissimilar polymers is one of the important factors that limit the application of polymers and their composites. We proposed a surface modification scheme of laser ablation or etching to improve the weldability of immiscible polymers effectively. Experimental studies on femtosecond ultraviolet (UV) laser ablation/etching, mid-infrared laser transmission welding (LTW), and related characterization and mechanical tests were carried out. The experimental results showed that laser ablation induced the deposition of abundant polar oxygen-containing groups on the surface of polycarbonate (PC), which improved the miscibility of PC and polyamide 66 with a glass fibre volume ratio of 30% (PA66GF30) and reduced the weak boundary layer (WBL), thereby improving their chemical bonding performance. Using the compatibilization mechanism induced by laser ablation, the bonding strength of the PC/PA66GF30 joint obtained by LTW was 13.7 MPa, which was much higher than that of the untreated joint (1.4 MPa). However, the grooves generated by laser etching could induce macro-anchoring effect of the hybrid joint. Based on the compatibilization mechanism and macro-anchoring effect, with the selection of appropriate welding power and etching parameters, the bonding strength of the PC/PA66GF30 joint was further increased to 29.7 MPa. This work has demonstrated the feasibility of laser surface treatment (especially etching) to significantly improve the welding strength of immiscible polymers and their composites.

Wet etching of gold on graphene for high-quality resist-free graphene surfaces

Wet etching of gold on graphene is challenging due to the weak adhesion of the resist mask to graphene. We report an operating procedure for alkali ion-free wet etching of gold on graphene using a mixture of hydrochloric and nitric acids (aqua regia) with a high lateral resolution down to 100 nm. We investigate the role of positive and negative resists, electron beam lithography (EBL) dose, hard-bake, oxygen etching, aging, and sensitivity to the etch parameters, such as the freshness of dilute aqua regia, etch time, and the order of etched samples. The negative-tone resist provides the best results. The over-dosed EBL exposure can enhance the resist adhesion, as hard-bake below the glass-transition temperature and well-defined wet etch of the resist-residua-free gold surface. We also present a cleaning procedure to avoid bubble formation after the hard bake. Our results demonstrate that wet etching of gold on graphene using aqua regia is a viable method for achieving high-quality resist-free graphene surfaces. This method has potential applications in graphene nanoelectronics and nanophotonics, where high-quality graphene surfaces are essential for device performance.

Comparison between etching techniques for solid-state nuclear track detector (CN-85) to develop alpha tracks

The present work aims to estimate and compare the etching parameters of Solid-state nuclear track detector (SSNTD) CN-85 with different etching techniques (Water bath, Ultrasound, Microwave, Oven and Plasma (Dry Etching)). CN-85 detectors were exposed in a direct contact to the sensitive face (notated face) for 15 s to alpha particles emitted from the radium-226 source (226Ra) of 4.87 MeV energy and 5 μCi activity. Small pieces with area (1 × 1) cm2 of CN-85 detectors were used. Using an optical microscope (model, N-200M). It has magnification of 400× to count the alpha tracks of CN-85 detectors. Tracks density and tracks diameters of CN-85 detector at different etching time from the five etching techniques were estimated. In addition, based on the experimental results, etching parameters related to the maximum track densities for CN-85 track detector are calculated. With etching efficiency value of ∼ 73%, microwave technique is the most efficient technique follow with plasma technique with (∼59%). The other three techniques had efficiencies three times less than microwave technique. Therefore, it can conclude that microwave etching technique is recommended for CN-85 detectors.

Enhancing the specific capacitance of a porous silicon-based capacitor by embedding graphene combined with three-dimensional electrochemical etching

A porous silicon-based capacitive structure with high specific capacitance is fabricated by three-dimensional electrochemical etching. As well as conventional planar electrochemical etching in two dimensions on the surface of a silicon chip, the lateral side walls of trenches engraved by a laser beam are also etched (third dimension). Platinum is deposited on both sides of the porous silicon film to create a capacitive structure that allows for stable measurement of the equivalent permittivity and specific capacitance of the trench-structured, layered porous silicon material. To eliminate the large parasitic effect due to the high roughness and air gaps between the metal layer and the porous silicon layer, nano-scale graphene is embedded into the surface pores of the porous silicon to enable good contact. After preliminary experiments, an etching approach based on a continuously decreasing current is adopted to obtain a strong porous silicon structure with long silicon pillars. Various laser engraving patterns were compared to determine the effect of three-dimensional etching. The results show that the increase in specific capacitance due to the laser trenches is positively correlated with the extent of lateral etching. The proposed method is suitable for improving the equivalent permittivity of the porous silicon layer without changing the device geometry or electrochemical etching parameters, and is also compatible with Si-VLSI technology.

Arrays of nano and micro inverted silicon structures via copper catalyzed chemical etching for effective light trapping

Nano/micro structuring of silicon (Si) via chemical approaches have currently acquired a lot of research interests owing to their excellent light trapping abilities in broad spectral range. Here, a comprehensive study on the fabrication of nano/micro-inverted structures via one-step copper (Cu) catalyzed chemical etching (CuCCE) of solar grade n-Si wafers employing the aqueous solution of Cu(NO3)2/HF/H2O2 in various compositions and their light trapping ability are reported. Influence of etch parameters, namely, Cu2+ ions concentration, HF/H2O2 compositions and surface properties of the wafers are systematically investigated on the evolution of different inverted nano- and micro-structured Si surfaces. Arrays of micron-sized inverted pyramids (μ-IP) and nano-micro-hybrid inverted pyramids (n-μ-HIP) have been fabricated on partial polished and as-cut solar grade Si wafers respectively in an optimized compositions of the solution (Cu(NO3)2, HF and H2O2 at 5 mM, 4.6 M and 0.55 M respectively) at 50 °C after 15 min. The surfaces exhibit solar weighted reflection as low as <7% and <5% respectively for a broad spectral range (400–1000 nm; AM1.5G). The n-μ-HIP-Si arrays also exhibited ∼8 fold enhanced Raman signal. Isotropic thinning of Si wafers, nano-porous, and craters like Si structures could also be obtained under appropriate etch conditions. Mechanism of the formation of such inverted structures under different etch conditions have been explained based on the Cu catalyzed, self-controlled electrochemical redox reactions and balancing act of anisotropic-isotropic etching of Si in the CuCCE etch bath. The excellent light trapping properties of the nano/micro structures is also explained. Moreover, the ‘proof of concept’ of application of the inverted nano/micro light trapping structures in the PEDOT:PSS/n-Si hybrid heterojunction solar cells with enhanced performance has also been shown. The Si surfaces via simple yet effective CuCCE process may find applications in other photosensitive devices as well as surface enhanced Raman spectroscopy.

Microlens array device for laser light shaping in laser scanning smart headlights.

We present, what we believe to be, a novel microlens array (MLA) scheme for laser light shaping in laser scanning smart headlight. The laser spot has a Gaussian distribution that may reach a high peak power density in the central part, which is called hot spot. When the laser beam is applied to a phosphor plate for luminous conversion, the hot spot of Gaussian beam causes thermal quench and decreases luminous efficacy. To avoid this effect, an MLA is used, so as to achieve a uniform energy distribution. In this study, we propose a laser scanning smart headlight fabricated by a new MLA structure, with an arrangement providing both light uniformity and shaping. The novel MLA is designed by two-dimensional micro-concave lens array yielding a flat-top beam. The flexible fabrication process employs laser drilling to shape the micro-hole array on the glass substrate surface and then etch it to form MLA without requiring any mask lithography process. The full-width half maximum (FWHM) of light output distribution can be adjusted by the glass etching parameters, and the light distribution could be controlled by the arranged layout of the array. Thus, beams with FWHM divergence ranging from 5° to 34° has been fabricated and characterized. The typical pixel shape is a rectangle with two different FWHMs in two orthogonal directions, and the fabrication method achieves this goal as well. This novel design and unique maskless process of the MLAs is a promising tool for development the next generation laser scanning smart headlight.

Investigations on black silicon nanostructures fabricated by reactive ion etching on highly curved surfaces

A large amount of valuable research on black silicon (b-Si) nanostructures has pushed its use further into application in recent years. However, the research results to be found are all related to plane substrates. For an investigation of b-Si structures on curved surfaces, they were fabricated on hemispherical silicon lenses using inductively coupled plasma reactive ion etching. It was possible to achieve different structure morphologies according to the selected etching parameters, analogous to their fabrication on Si wafers. Scanning electron microscopy inspections of the structure morphology were carried out to study the homogeneity across the lens surface as well as the orientation of the structures. Simulations of the bent electric field within the etching chamber and the resulting ion trajectories explain the underlying etching process that creates structures approximately perpendicular to the curved lens surface. Optical reflectance measurements confirm the findings on homogeneity and orientation.

Controllable Fabrication of Silicon Nanopore Arrays by Two-Step Inductively Coupled Plasma Etching Using Self-Assembled Anodic Aluminum Oxide Mask

Silicon nanopore arrays (SiNPs) were prepared by a two-step inductively coupled plasma (ICP) etching process using a self-assembled anodic aluminum oxide film mask. The influence of etching parameters (first-step etching time, Cl2 proportion in the etching gas, etching pressure, ICP power, and radio frequency (RF) power) on the morphology of the SiNPs were systematically investigated. The results revealed that the first step of ICP etching can effectively remove the barrier layer of the mask. Higher Cl2 proportion and lower etching pressure increase the chemical corrosion and physical bombardment of ICP etching, respectively, which may damage the porous morphology. ICP power affects both chemical reaction etching and physical bombardment, but the RF power mainly affects physical etching. The etching rate is positively correlated with Cl2 proportion and RF power, and negatively correlated with etching pressure. The optimized first-step etching time, Cl2/Ar ratio, etching pressure, ICP power and RF power for high-quality SiNPs are approximately 10 s, 60%, 7 mTorr, 900 W and 100 W, respectively. Precise control of the pore size and depth of the SiNPs can be achieved using this controllable growth process. These results demonstrate a simple and controllable way to achieve good quality SiNPs with desired sizes.

Sensitivity reduction and track parameters fading of PADC irradiated to high energy ions after twenty-seven years

PADC track etching parameters measured in 1994 and 2021 were compared. Track fading over the longest time (27 years) was determined. The etching conditions of the samples were reproduced as closely as possible, namely 6.25M NaOH and 50 °C. The difference in track parameters of diameter, bulk, track etch rate, and detector sensitivity with detector depth for 1.89 GeV N, 0.96 GeV C, 19.2 GeV Ar, 46.48 GeV Fe, and 17.7 GeV Ni have been measured. Track diameter growth with etching time, te was observed for N, C, Ar, Fe, and Ni tracks and compared with 1994 data. Clear larger bulk and track etch rates have been observed for the current measurements compared to the previous ones for the 5 ions under investigation. A significant reduction in PADC sensitivity due to fading was observed after these twenty-seven years. The higher the ion's LET, the more the fading. The reduction rate was calculated, and a sensitivity correction formula was introduced. Detector sensitivity at any previous time can be calculated from the current sensitivity by the suggested equation. The physical and chemical explanations for the fading changes in different track parameters were suggested.

Optimization of fs + ps double-pulse sequence parameters for laser-assisted chemical etching of microchannels in fused silica

Developing laser fabricating technology to improve the etching rate of microchannels is of great significance for the development of microfluidic devices. In this paper, the laser processing parameters of the fs + ps double-pulse sequence, including temporal delay and pulse energy ratio, have been investigated to optimize the fabrication of microchannels, in order to obtain a high etching rate. As a result, the optimal energy ratio could be obtained at Efs:Eps = 2:1 in negative delays. Furthermore, the etching rate of microchannels was significantly improved by 40.8% compared with those written by fs + fs double-pulse sequence with an energy ratio of 1:1. This improvement is possibly because fs sub-pulse excited seed electron may trigger impact ionization via an efficient energy absorption process within the following ps sub-pulse, this energy accumulation and subsequent thermal diffusion lead to an increase of the modified area. The aforementioned results possibly offer an effective route to improve the etching rate of microchannels which is in favor of accelerating the fabrication of three-dimensional microfluidic devices.

In situ diagnostics of the Si etching structures profile in ICP SF6/C4F8 plasma: Macrostructures

In this work, we studied the influence of technological parameters of plasma chemical etching of silicon on silicon etching rate, photoresist etching rate, etching selectivity of silicon in relation to a photoresist, and sidewall angle of etched structures. It was found that the silicon etching rate increases with raising percentage of SF6 in the gas mixture (25%–50%), pressure (1–2.5 Pa), high-frequency (HF) power (1000–2000 W), and bias voltage module (15–75 V) and decreases with a raising total flow rate of the gas mixture (5–35 SCCM) due to the increasing passivation efficiency of the sample surface. The etching selectivity increases with a raising percentage of SF6 and pressure and decreases with the raising total gas flow rate, HF power, and bias voltage module due to different influences of technological parameters on the photoresist etching rate. In addition, based on the obtained results, a common regularity between the sidewall angle and the optical emission spectra was revealed. The method of in situ diagnostics was proposed, namely, controlling the sidewall angle by a ratio of emission intensities of a carbon line (517.1 nm) to a fluorine line (685.8 and 703.9 nm) designated as parameter X. It was found that the sidewall angle of etched structures takes certain values depending on the value of the X parameter. The ranges of X values at which the sidewall angle is acute, right, and obtuse were estimated. So, at values of X from ≈0.15 to ≈0.35, an acute angle (from 81° ± 0.5° to 89° ± 0.5°) is obtained; at X from ≈0.35 to ≈0.42, a right angle is obtained (90° ± 0.5°); and at X from ≈0.42 to ≈0.75, the values of the sidewall angle are in the range from 91° ± 0.5° to 94° ± 0.5°, no matter which technological parameters were set. Experiments were conducted for etching windows with linear dimensions from 0.5 × 20 to 2 × 20 mm.

Large‐Scale Formation of Uniform Porous Ge Nanostructures with Tunable Physical Properties

AbstractPorous germanium (PGe) nanostructures attract a lot of attention for various emerging applications due to their unique properties. Consequently, there is an increasing need for the development of low‐cost synthesis routes that are compatible with large‐scale production. Bipolar electrochemical etching (BEE) is a widely used solution for producing porous Ge layers. However, the lack of controllable production of large‐scale uniform PGe layers is the limiting factor for mainstream applications. Large‐scale homogeneous PGe layers formation is demonstrated by improving the BEE process. The PGe structures demonstrate excellent homogeneity in thickness and porosity, with a relative variation of below 2% across the 100 mm wafer. Furthermore, this process enables accurate tuning of the PGe's physical properties through variation of the etching parameters. PGe structures with porosity ranging from 40% to 80% and an adjustable thickness, while preserving low surface roughness are demonstrated, giving access to a large variety of PGe nanostructures for a wide range of applications. Ellipsometry and X‐ray reflectivity are employed to measure the porosity and thickness of PGe layers, providing fast and non‐destructive methods of characterization. These findings lay the groundwork for the large‐scale production of high‐quality PGe layers with on‐demand characteristics.

Comparative study on traditional and new etchants for radon monitoring using Poly(allyl diglycol carbonate) (PADC) and identification of (Na3H(CO3)2.2H2O) in etched products

A comparative study is conducted on Traditional Etchants (NaOH/H2O, KOH/H2O) and New Etchants viz. NaOH/Methanol, NaOH/Ethanol and NaOH/1-propanol for Poly(allyl diglycol carbonate) (PADC) used in Radon monitoring. Molar concentration of traditional etchants NaOH/H2O and KOH/H2O is varied from 1 M to 6 M and etching temperature is varied from 30 °C to 80 °C to verify optimal etching parameter. Etching is done for 8 to 9.5 h in the steps of 30 min. An average bulk etch rate (Vb) of 1.4μm/h and 1.7μm/h for NaOH/H2O and KOH/H2O is calculated respectively under optimal etching conditions. Optimal reported concentrations of 1.5 M, 1.5 M and 1 M respectively, are used to make standard NaOH/Methanol, NaOH/Ethanol and NaOH/1-propanol solutions. Track densities, track diameters, bulk etch rate (Vb), track etch rate (Vt), etching time, variation in mass and thickness for both traditional and new etchants are calculated and compared. Traditional etchants take much longer time (5 to 7 h) for etching with initial swelling due to absorption of etchant on the surface of detector due to broken molecular chains, causing increase in mass and thickness of detectors for initial 0.5 to 1 h of etching which are measured with digital balance (±0.0001 g) and digital micrometer (±0.001 mm) respectively. New etchants take short time for etching (30 min approx.). There is no initial increase in mass and thickness of detectors due to short etching time and high Vb of new etchant. Traditional etchants give high track densities with low Vb and Vt while new etchants gives low track density with high Vb and Vt. New tracks formation is rare in new etchants as compared to traditional etchants. An average radon concentration level of 21.8 kBqm−3 is calculated from detectors etched in traditional etchants while new etchants do not provide any useful information about radon track density to calculate radon concentration for the given samples. Trona i-e Na3H(CO3)2.2H2O is identified as a common product formed in the etched products of PADC etched in either of the etchants i.e. traditional etchants and new etchants, using X-ray powder diffraction (XRPD) analysis.

Synthesis and lithium ion storage performance of novel two dimensional vanadium niobium carbide (VNbCTx) MXene

Two-dimensional double transition metal carbides/nitride with unique out-of-plane arrangement of two metal atoms is emerging as a new pseudocapacitor material and attracting wide attention in the field of energy storage. Herein, fabrication of a novel 211-phase vanadium niobium carbide (VNbCTx) MXene by selectively etching the Al atomic layer from its VNbAlC MAX phase is reported for the first time. Effect of etching parameters on the microstructure, crystallinity, and electrochemical property of multilayer VNbCTx is examined. As the electrode material of lithium ion batteries, VNbCTx show a higher specific capacity of 520.5 mAh g−1 at 0.1 A g−1 and promising cycle stability. This work provides additional understanding about the synthesis and storage performance of double transition metal MXene, which will benefit the development of novel double transition metal MXene for energy storage applications.

CMOS-compatible manufacturability of sub-15 nm Si/SiO2/Si nanopillars containing single Si nanodots for single electron transistor applications

This study addresses the complementary metal-oxide-semiconductor-compatible fabrication of vertically stacked Si/SiO2/Si nanopillars (NPs) with embedded Si nanodots (NDs) as key functional elements of a quantum-dot-based, gate-all-around single-electron transistor (SET) operating at room temperature. The main geometrical parameters of the NPs and NDs were deduced from SET device simulations using the nextnano++ program package. The basic concept for single silicon ND formation within a confined oxide volume was deduced from Monte-Carlo simulations of ion-beam mixing and SiO x phase separation. A process flow was developed and experimentally implemented by combining bottom-up (Si ND self-assembly) and top-down (ion-beam mixing, electron-beam lithography, reactive ion etching) technologies, fully satisfying process requirements of future 3D device architectures. The theoretically predicted self-assembly of a single Si ND via phase separation within a confined SiO x disc of <500 nm3 volume was experimentally validated. This work describes in detail the optimization of conditions required for NP/ND formation, such as the oxide thickness, energy and fluence of ion-beam mixing, thermal budget for phase separation and parameters of reactive ion beam etching. Low-temperature plasma oxidation was used to further reduce NP diameter and for gate oxide fabrication whilst preserving the pre-existing NDs. The influence of critical dimension variability on the SET functionality and options to reduce such deviations are discussed. We finally demonstrate the reliable formation of Si quantum dots with diameters of less than 3 nm in the oxide layer of a stacked Si/SiO2/Si NP of 10 nm diameter, with tunnelling distances of about 1 nm between the Si ND and the neighboured Si regions forming drain and source of the SET.

Mechanical, chemical and wetting properties of a superhydrophobic surface based on functionalized ZrO2 on stainless steel

A stable superhydrophobic FAS-ZrO2 (FZr-ESS) surface was created by chemically etching and modifying a 304 stainless steel substrate. The effect of etching parameters such as time and temperature on the surface wetting properties was studied and optimized. The etched steel surface exhibited a honeycomb-like microstructure that, coupled with the low surface energy of the fluorinated ZrO2 nanoparticles, produced a FZr-ESS surface with a surface contact angle (CA) of 165.9° and a sliding angle (SA) of 1.7°. The presence of highly stable functionalized ZrO2 conjugated to the steel matrix contributed to the surface's outstanding mechanical stability, as confirmed by tape peeling and sandpaper abrasion tests. Furthermore, the FZr-ESS surface demonstrated exceptional chemical stability under a variety of pH conditions due to its excellent water repellency. An electrochemical test showed that the resulting surface was highly resistant to corrosion, with the corrosion current density reduced by nearly two orders of magnitude compared to bare stainless steel. The superhydrophobic FZr-ESS surface also displayed excellent long-term stability, wetting diversity, and self-cleaning behavior, making it highly versatile for a range of applications.

Nanoscale Phase Change Material Array by Sub-Resolution Assist Feature for Storage Class Memory Application

High density phase change memory array requires both minimized critical dimension (CD) and maximized process window for the phase change material layer. High in-wafer uniformity of the nanoscale patterning of chalcogenides material is challenging given the optical proximity effect (OPE) in the lithography process and the micro-loading effect in the etching process. In this study, we demonstrate an approach to fabricate high density phase change material arrays with half-pitch down to around 70 nm by the co-optimization of lithography and plasma etching process. The focused-energy matrix was performed to improve the pattern process window of phase change material on a 12-inch wafer. A variety of patternings from an isolated line to a dense pitch line were investigated using immersion lithography system. The collapse of the edge line is observed due to the OPE induced shrinkage in linewidth, which is deteriorative as the patterning density increases. The sub-resolution assist feature (SRAF) was placed to increase the width of the lines at both edges of each patterning by taking advantage of the optical interference between the main features and the assistant features. The survival of the line at the edges is confirmed with around a 70 nm half-pitch feature in various arrays. A uniform etching profile across the pitch line pattern of phase change material was demonstrated in which the micro-loading effect and the plasma etching damage were significantly suppressed by co-optimizing the etching parameters. The results pave the way to achieve high density device arrays with improved uniformity and reliability for mass storage applications.

Development of high uniformity Al1-xScxN piezoelectric film stack dry etching process on 8-inch silicon wafers

This paper have investigated the basic properties of inductively coupled plasma reactive ion etching (ICP-RIE) of scandium doped aluminum nitride (Al1-xScxN) thin films on 8-inch silicon wafers, and presented a pretreatment scheme which can effectively improve the etching uniformity and wafer yield in the mass fabrication of Al1-xScxN-MEMS (micro-electromechanical systems) devices. Based on BCl3/Ar pretreatment and Cl2/Ar main etching scheme, an etching rate of 128 nm/min is obtained, with the low nonuniformity, and selectivity of 1.8 with respect to the loss of molybdenum (Mo) electrode is achieved, respectively. The relationship between etching parameters and etching uniformity is revealed in detail by the 5-step Al1-xScxN etching model. Meanwhile, to optimize the etching compatibility in the fabrication of Al1-xScxN-piezoelectric MEMS devices, a variety of etching masks (e.g. photoresist and silicon dioxide) are respectively used to obtain the consistent sidewall profile at different locations, with photoresist of 24° and silicon dioxide of 57°.