Etching Behavior Research Articles

Effects of grain size, dislocation density, and texture type on the etching behavior of Cu target in magnetron sputtering process

Abstract Copper thin film is commonly applied in the microelectronics and battery industries, and environmentally friendly magnetron sputtering process is one of the main coating processes. The effects of grain size, dislocation density, and texture type of Cu target on sputtering efficiency were researched in this work. High-purity copper cast ingots were rolled into plates. Pieces were then cut from different surfaces of the plates and assembled into the targets named as Target 1, Target 2, and Target 3 for magnetron sputtering. To investigate the etching behavior of the three targets, EBSD technology was utilized for analysis, and the micro-morphologies of the etching grooves were observed using SEM. After the sputtering process, the weight loss rate and etching depth of the various targets were measured to compare the respective sputtering efficiency. Target 1 exhibited the highest sputtering weight loss rate at any time period compared to Target 2 and Target 3, and reached its maximum depth after every 15 minutes of sputtering. In the first 45 minutes, the etching depth of Target 2 was slightly greater than that of Target 3. While the etching depth of Target 3 increased significantly in the last 15 minutes compared to that of Target 2. The most significant factor influencing the sputtering efficiency of the target material was grain size, with finer grains leading to higher sputtering efficiency. The dislocation density had a greater impact in the first 30 minutes, but the texture type became more important as the sputtering process continued.

Local Strain-Dependent Etching Patterns of Chemical Vapor Deposited Molybdenum Disulfide.

This study reveals a local strain-dependent etching behavior that enables the formation of distinguished etching patterns in differently strained chemical vapor deposited (CVD) 2D molybdenum disulfide (MoS2) monolayers. It is demonstrated that when the local tensile strain of CVD 2D MoS2 is as uniformly low as ɛ ≈ 0.33% or less, the oxidative etching pattern possesses conventional triangular etching pits (TEPs), while when the local tensile strain is as uniformly high as ɛ ≈ 0.55% or larger, the oxidative etching pattern consist of uniformly oriented hexagonal etching channels (HECs). More interestingly, when the CVD 2D MoS2 monolayer has heterogenous strain distribution from ɛ ≈ 0.55% (center region) to ɛ ≈ 0.33% (perimeter region), the oxidative etching pattern comprise of non-uniformly hexagonal-mixed-parallel etching channels (HPECs). The further characterization and analysis reveal the formation mechanism of such strain-dependent etching patterns is built on the local strain-related fractures propagation under oxidative etching, as well as the anisotropy fractures-based oxidative etching kinetics. This study may enhance the understanding of the relationship between etching and growth features of 2D TMDs, and paves the way to etching-nanostructured (or defect) engineering of 2D TMDs and other 2D materials for potential applications in electrocatalysis and optoelectronics.

Nonhalogen Dry Etching of Metal Carbide TiAlC by Low-Pressure N2/H2 Plasma at Room Temperature.

Ternary metal carbide TiAlC has been proposed as a metal gate material in logic semiconductor devices. It is a hard-to-etch material due to the low volatility of the etch byproducts. Here, a simple, highly controllable, and dry etching method for TiAlC has been first presented using nonhalogen N2/H2 plasmas at low pressure (several Pa) and 20 °C. A capacitively coupled plasma etcher was used to generate N2/H2 plasmas containing active species, such as N, NH, and H to modify the metal carbide surface. The etch rate of TiAlC was obtained at 3 nm/min by using the N2/H2 plasma, whereas no etching occurred with pure N2 plasma or pure H2 plasma under the same conditions. The surface roughness of the TiAlC film etched by N2/H2 plasma was controlled at the atomic level. A smooth etched surface was achieved with a root-mean-square roughness of 0.40 nm, comparable to the initial roughness of 0.44 nm. The plasma properties of the N2/H2 plasmas were diagnosed by using a high-resolution optical emission spectrometer, detecting the NH molecular line at 336 nm. The etching behavior and plasma-surface reaction between N2/H2 plasma and TiAlC were investigated by using in situ spectroscopic ellipsometry, in situ attenuated total reflectance-Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy. The findings indicate that the N-H, C-N, and Ti(Al)-N bonds form on the TiAlC surface etched by the N2/H2 plasmas. The mechanism for etching of TiAlC involving transformation reactions between inorganic materials (metal carbides) and inorganic etchants (N2/H2 plasma) to form volatile organic compounds such as methylated, methyl-aminated, and aminated metals is proposed. Nonhalogen or nonorganic compound etchants were used during the etching process. The study provides useful insights into microfabrication for large-scale integrated circuits.

Effect of Cl2 Radical on Dry Development of Spin-Coated Metal Oxide Resist.

In this study, the effects of Cl2 radicals on dry development of spin-coated metal oxide resist (MOR) and changes in its surface binding states were investigated to verify the mechanism of dry development. Dry development characteristics of tin hydroxide (Tin OH), which is one of the MOR candidates for next generation lithography, were investigated as functions of process time and temperature using a Cl2 radicals source. Non-UV-exposed Tin OH film showed a linear etch rate (1.77 nm/min) from the initial thickness of ∼50 nm, while the UV-exposed film showed slower etch behavior (1.46 nm/min) in addition to the increase of film thickness for up to 3 min during the Cl2 radical dry development. UV-exposed photoresist (PR) contained more oxygen (Sn-O bonding) in the film due to the removal of butyl compounds from the clusters during the UV exposure process. Therefore, due to the lower reaction of chlorine radicals with Sn-O in the UV-exposed Tin OH than the other bindings, the non-UV-exposed PR was preferentially removed compared to the UV-exposed PR. As the temperature decreases, the overall etch rate decreases, but the difference in etch rate between exposed and unexposed Tin OH becomes larger. Finally, at a substrate temperature of -20 °C, the non-UV-exposed Tin OH with a thickness of 50 nm was completely removed, while ∼30 nm thick PR remained for UV-exposed Tin OH. Eventually, a negative tone development was possible with Cl2 radical plasma due to the difference in activation energy between the UV-exposed and non-UV-exposed films. It is believed that dry development using Cl2 radicals will be one of the most important process techniques for next-generation patterning to remove problems such as pattern leaning, line edge roughness, residue, etc., caused by wet development.

The Etching Behaviour and Fluorine-Based-Plasma Resistance of YOF Coatings Deposited by Atmospheric Plasma Spraying

There is a high demand for plasma-resistant coatings that prevent the corrosion of the internal ceramic components of plasma etching equipment, thereby reducing particle contamination and process drift. Yttrium oxyfluoride (YOF) coatings were prepared using atmospheric plasma spraying (APS) with commercially available YOF/YF3 powder mixtures; namely YOF 3%, YOF 6%, and YOF 9%. The etching behaviour of YOF and yttrium oxide (Y2O3) coatings was investigated using an inductively coupled plasma consisting of NF3/He. X-ray photoelectron spectroscopy (XPS) showed that the YOF 6% coating had the thickest fluorinated layer. The scanning electron microscope (SEM) examination revealed that the YOF 6% coating showed exceptional resistance to erosion and generated a reduced quantity of contaminated particles in comparison to Y2O3. Consequently, it is more suitable as a protective material for the inner wall of reactors. The YOF coatings exhibit excellent stability and high resistance to erosion, indicating their appropriateness for use in the semiconductor industry.

Influence of bias voltage on the Ar/CH2F2/O2 plasma etching of Si3N4 films

The etching mechanism of silicon nitride (Si3N4) films depending on peak-to-peak bias voltage ( Vpp ) in an Ar/CH2F2/O2 gas-mixture plasmas for high-aspect-ratio etching process was investigated. It was observed that the Si3N4 film etch rate initially decreased with an increase in the Vpp up to 3630 V, but then increased beyond this threshold. This unusual etching behavior can be attributed to the formation of a modified layer on the surface of the Si3N4 film. The characteristics of the modified layer, such as thickness and atomic composition, were found to be strongly influenced by the ion energy and gas chemistry of the process conditions.

Porous GaN Nanopyramids: Advancing Beyond Conventional Nanostructures for High‐Brightness InGaN/GaN Quantum Wells Emission

AbstractGaN nanostructures hold significant promise in advancing nanoscale light‐emitting devices. However, significant progress remains elusive, possibly due to the absence of innovative approaches. Beyond the smaller size of GaN nanostructures, the main interest lies in growing InGaN active layers on semi‐ and non‐polar orientations. Nevertheless, it is evident that while leveraging such a method holds initial promise, this approach may eventually reach its limits, prompting the need for fresh perspectives. In this manuscript, electrochemical etching is utilized to fabricate porous GaN nanopyramids. Given the absence of prior studies on electrochemical etching of GaN nanostructures, its etching behavior is investigated, revealing its selectivity concerning doping concentration and geometry. Furthermore, how the choice of electrolyte can differently impact the optical response of the etched template is explored. Subsequently, an InGaN/GaN quantum wells shell is grown as the active region. The significance of the approach is evidenced by a tenfold enhancement in photoluminescence emission. Porous nanopyramids demonstrate a higher internal quantum efficiency of 44.7% and faster radiative recombination time. Additionally, finite difference time domain simulation reveals a twofold increase in light extraction efficiency. This research will lead the way toward the development of a new class of nanostructures offering potential advancements in optoelectronic devices.

The oxygen plasma etching behavior onto diamond-like carbon coating for micro-texturing: Experimental and molecular dynamics study

The oxygen plasma etching behavior onto diamond-like carbon coating for micro-texturing: Experimental and molecular dynamics study

Analysis of silicon surfaces etched in aqueous HF-(HBr)–Br2-mixtures

Solutions containing hydrofluoric acid (HF), hydrobromic acid (HBr) and bromine (Br2) were investigated as novel acidic, NOx-free mixtures for wet-chemical etching of silicon wafers. HF–Br2-mixtures exhibit isotropic etching behaviour towards silicon, etch rates up to 4.0 ​μm ​min−1 were observed at room temperature, which are higher than the etch rates of commercially used alkaline solutions. HF–HBr–Br2-mixtures show anisotropic etching behaviour, texturing the surface of monocrystalline silicon wafers with random upright or random inverted pyramidal structures. Etch rates up to 2.4 ​μm ​min−1 were observed, the etch rate increases linearly with the concentration of Br2 in the etching solution. Silicon surfaces were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The light trapping efficiency of wafers etched by HF–HBr–Br2 solutions was compared to commercially available textured wafers by UV/Vis-reflectivity measurements indicating lower reflectivities for the HF–HBr–Br2-treated samples. A reaction scheme for the anisotropic dissolution of silicon in bromine-containing aqueous HF-solutions is proposed, which involves bromine as oxidizing agent.

Quasi-3D fracture acidizing simulation based on discrete virtual internal bond method

Fracture acidizing (FA) is the most effective stimulation technique for carbonate reservoirs. It involves the hydro-chemical coupling process. To more efficiently simulate FA, a quasi-3D discretized virtual internal bond (DVIB) is developed, in which a certain height is assigned to each bond and the rock is considered to consist of heterogeneous quasi-3D bond cells. The fracture is allowed to transversely cut through these bond cells. The macro fracture aperture fluctuation is characterized by the various apertures embedded in micro bonds. As the acid fluid flows through the fracture, the acid dissolves the bond to widen the aperture. The bond permeability is associated with the its aperture. Through this approach, the complicated hydro-chemical coupling process is reduced to 1D bond dissolution problem, which significantly improves the efficiency of FA simulation. The simulation examples show that the acid reactant transportation, the acid etching behaviors and the fracture acidizing process can be well simulated. It provides an efficient approach to FA simulation.

Influences of deformation defects on etching behaviors of high-strength and high-conductivity Cu alloy for lead frame

With increasing integration of the semiconductor devices, the requirements on size accuracy and surface quality of the lead frame are higher. Cold-rolling and low-temperature aging are usually used in processing of the Cu alloy for lead frame, which generate/eliminate the deformation defects that affect the etched surface morphology and roughness, while the influence mechanisms have not been well revealed. In this study, the CuCrSn alloy was used as the experimental material, which was cold-rolled to different degree and then aged at 450 °C for different time, and the microstructures and etched surfaces of the specimens were characterized. The results show that etched surface morphologies of grains with different orientations in the coarse-grained Cu alloy are different. With increasing cold-rolling deformation, the influences of grain orientation become less obvious, and the dislocation groups on the slip planes result in grooves approximately parallel to the rolling direction, meanwhile the surface uniformity are improved and the surface roughness decreases. For the 80 % cold-rolled Cu alloy, the density of grooves decreases with increasing aging time and elimination of the dislocations, and the etched surface roughness decreases firstly and then tends to be stable. The etched surface changes significantly and the surface roughness increase obviously after recrystallization of the specimen.

Characterization of an RF-excited broad beam ion source operated with a mixture of CHF3 and O2

The composition and ion energy distributions of the main ion species of an ion beam were recorded and analyzed. The RF-type broad beam ion source was operated with a mixture of CHF3 and O2. A plasma bridge neutralizer operating with Ar was employed for ion beam neutralization. The data were collected with an energy-selective mass spectrometer (ESMS). The mass spectrum showed numerous ion species, beginning with ionized molecules, dissociation products of the process gases and products from reactions with background gas and the plasma discharge vessel, and the extraction system. For a quantification of the ion beam composition, the mass dependent transmission functions for two ESMS were determined. The ion energy distributions show that, in comparison to operation with inert gases, there are additional slower ions present. These ions can be related to dissociation processes outside of the ion beam source. As a result of their typically lower etching yield, these slower ions affect the etching behavior.

Optimization of waveguide fabrication processes in lithium-niobate-on-insulator platform.

Lithium niobate (LN) is used in diverse applications such as spectroscopy, remote sensing, and quantum communications. The emergence of lithium-niobate-on-insulator (LNOI) technology and its commercial accessibility represent significant milestones. This technology aids in harnessing the full potential of LN's properties, such as achieving tight mode confinement and strong overlap with applied electric fields, which has enabled LNOI-based electro-optic modulators to have ultra-broad bandwidths with low-voltage operation and low power consumption. Consequently, LNOI devices are emerging as competitive contenders in the integrated photonics landscape. However, the nanofabrication, particularly LN etching, presents a notable challenge. LN is hard, dense, and chemically inert. It has anisotropic etch behavior and a propensity to produce material redeposition during the reactive-ion plasma etch process. These factors make fabricating low-loss LNOI waveguides (WGs) challenging. Recognizing the pivotal role of addressing these fabrication challenges for obtaining low-loss WGs, our research focuses on a systematic study of various process steps in fabricating LNOI WGs and other photonic structures. In particular, our study involves (i) careful selection of hard mask materials, (ii) optimization of inductively coupled plasma etch parameters, and finally, (iii) determining the optimal post-etch cleaning approach to remove redeposited material on the sidewalls of the etched photonic structures. Using the recipe established, we realized optical WGs with total (propagation and coupling) loss value of -10.5 dB, comparable to established values found in the literature. Our findings broaden our understanding of optimizing fabrication processes for low-loss lithium-niobate waveguides and can serve as an accessible resource in advancing LNOI technology.

Investigating the expansion behavior of silicon nanoparticles and the effects of electrolyte composition using a graphene liquid cell

Understanding the volume expansion behavior of Si anodes and their interaction with electrolyte environments is crucial for developing high-performance lithium-ion batteries (LIBs). This study utilizes a graphene liquid cell for in situ imaging to systematically investigate the volume expansion and etching behavior of Si anode nanoparticles in different electrolyte environments. Comparative experiments on Si@C core-shell nanoparticles assess their volume expansion dynamics. The findings reveal significant variation in the expansion rate of nano Si depending on the electrolyte environment, with chemical etching observed under specific conditions. Conversely, Si@C core-shell structures show mitigated expansion due to the confinement effect of the carbon matrix. Battery performance experiments validate these results, demonstrating the excellent cycling stability of Si@C anodes. Various coating agents are explored to optimize Si@C structures, with dopamine thin layer coating exhibiting the best cycling stability. This study offers fundamental insights into Si anode expansion, electrolyte effects, and carbon coating impacts, advancing LIB technology.

Photochemical wet etching of (0 0 1) plane ß-phase Ga2O3, and its anisotropic etching behavior

The photochemical (PC) wet etching behavior of (001) plane β-phase Ga2O3(β-Ga2O3)single crystal was investigated using potassium hydroxide etchant solution under ultraviolet illumination in the temperature range of 80–95 °C. The etch rate was 1.65 nm/min at 80 °C, and increased up to 4.88 nm/min at 95 °C. The etch rate of the (001) plane β-Ga2O3shows strong temperature dependence with the activation energy of 0.798 eV. The PC wet etching characteristics of the (001) plane β-Ga2O3was compared with those of (2¯01) and (010) plane β-Ga2O3. The etch rates increased in order of the (010), (2¯01), and (001) plane, which is accordance with the increasing surface energy trend. The oval line-shaped grooves aligned along [010] direction were observed on the etched (001) plane β-Ga2O3 crystal surface after 30 min. PC wet etching at 80 °C.

High-rate etching of silicon oxide and nitride using narrow-gap high-pressure (3.3 kPa) hydrogen plasma

We investigated the etching behavior of silicon oxide (SiO x ) and silicon nitride (SiN x ) in narrow-gap, high-pressure (3.3 kPa) hydrogen (H2) plasma under various etching conditions. Maximum etching rates of 940 and 240 nm min−1 for SiO x and SiN x , respectively, were obtained by optimizing the H2 gas flow rate. The dependence of the etching rate on gas flow rate implied that effective elimination of etching products is important for achieving high etching rates because it prevents redeposition. The sample surfaces, especially the oxide surfaces, were roughened and contained numerous asperities after etching. Etching rates of both SiO x and SiN x decreased as the temperature was raised. This suggests that atomic H adsorption, rather than H-ion bombardment, is an important step in the etching process. X-ray photoelectron spectroscopy revealed that the etched nitride surface was enriched in silicon (Si), suggesting that the rate-limiting process in high-pressure H2 plasma etching is Si etching rather than nitrogen abstraction. The etching rate of SiO x was three times higher than that of SiN x despite the higher stability of Si–O bonds than Si–N ones. One reason for the etching difference may be the difference between the bond densities of SiO x and SiN x . This study presents a relatively non-toxic, low-cost, and eco-friendly dry etching process for Si-based dielectrics using only H2 gas in comparison with the conventional F-based plasma etching methods.

Effect of Aging on Fracture Load and Reliability of Cemented Glass-Ceramics.

To evaluate the influence of aging on the fracture load (Lf) and reliability of glass-ceramics after different etching protocols. Specimens were fabricated and divided according to the etching Ame (10% hydrofluoric acid [HF] for 20 seconds, 40 seconds, and 60 seconds). Etched surfaces were examined under microscopy. The ceramics were resin-cemented to a dentin analog material. Samples were split into two groups (n = 20 each) and tested after 24 hours (I) or stored in 37° water for 1 year (A). A compressive load (0.1 mm/minute) was applied to the samples unAl failure was detected by acoustic emission. The influence of aging on the Lf was tested by two-way ANOVA and Tukey tests (α = .05). The characteristic fracture load (L0) and Weibull modulus (m) values were calculated. Lithium silicate (LS) etching for 20 seconds resulted in the highest immediate Lf, which was significantly decreased after aging (P ≤ .05). Water storage had no effect on the Lf of glass-ceramic etched for 40 and 60 seconds (P > .05). For lithium disilicate (LD), the etching time had no significant effect on the immediate or aged Lf (P > .05). The Lf was significantly reduced after aging (A) for LD (P ≤ .05). Radial cracks were the predominant failure mode. Surface topography was more regular after lower etching times for LD and after higher times for LS. After 1 year of water-assisted aging, the evaluated etching times had no influence on the load-bearing capacity and structural reliability of resin-bonded glass-ceramics.

Microstructural characterization and inductively coupled plasma-reactive ion etching resistance of Y2O3–Y4Al2O9 composite under CF4/Ar/O2 mixed gas conditions

In the semiconductor manufacturing process, when conducting inductively coupled plasma-reactive ion etching in challenging environments, both wafers and the ceramic components comprising the chamber’s interior can be influenced by plasma attack. When ceramic components are exposed to long-term plasma environments, the eroded components must be replaced. Furthermore, non-volatile reactants can form and settle on semiconductor chips, acting as contaminants and reducing semiconductor production yield. Therefore, for semiconductor processing equipment parts to be utilized, it is necessary that they exhibit minimized generation of contaminant particles and not deviate significantly from the composition of conventionally used Al2O3 and Y2O3; part must also last long in various physicochemical etching environment. Herein, we investigate the plasma etching behavior of Y2O3–Y4Al2O9 (YAM) composites with a variety of mixing ratios under different gas fraction conditions. The investigation revealed that the etching rates and changes in surface roughness for these materials were significantly less than those of Y2O3 materials subjected to both chemical and physical etching. Microstructure analysis was conducted to demonstrate the minimization of crater formation. Mechanical properties of the composite were also analyzed. The results show that the composite can be commercialized as next-generation ceramic component in semiconductor processing equipment applications.

Understanding the contributions of F–, HF, and HF2– to the etching of SiO2 and unveiling the reaction kinetics to represent etching behavior of SiO2 up to pH 5

Understanding of the silicon dioxide (SiO2) etching mechanism in hydrofluoric acid (HF) solutions is important in semiconductor manufacturing processes. A study on the previous SiO2 etching mechanism claimed that only difluoride (HF2–) participated in SiO2 etching. However, in this study, it was observed that the etching of SiO2 occurred in the HF solution, where difluoride barely existed. Hence, a new SiO2 etching mechanism and reaction rate were proposed. Various concentrations of HF and ammonium fluoride (NH4F) under varying pH conditions were used to etch SiO2, leading to an SiO2 etching rate of 510[F–] + 610[HF] + 2890[HF2–] (Å/min). HF2– was the primary contributor to SiO2 etching; however, unlike the previous SiO2 etching mechanism, the effects of F– and HF on the etching of SiO2 were included in the rate of SiO2 etching. The SiO2 etching rate, considering the reactions between various fluorine species with varying SiO2 surface states, effectively represented the SiO2 etching behavior under various conditions over a broader pH range, up to pH 5. Controlling the ratio of the fluorine species, F–, HF, and HF2–, our etching model could also be extended to the selective etching of SiO2.

Anisotropic etching behavior and topography formation mechanism of silicon solar cell surface textured by atmospheric plasma

Atmospheric plasma etching (APE) has been used to texture Si surfaces due to anisotropic material removal capability. Controlling features and size of the light-trapping structure are keys to improving the reflection performance of silicon (Si) solar cells, which need to fully understand the interfacial etching behavior and the microscopic topography formation mechanism of the Si surface. In this study, microwave plasma with a temperature below 100 °C is employed to investigate the dependence of microstructure evolution on the O/F atom ratios in plasma. The results show that as the O/F atom ratios increase, the microstructure of the Si surface changes from square opening pits to spherical opening pits. High-resolution transmission electron microscopy and x-ray photoelectron spectroscopy analyses indicate that the exciting F atoms dominate the orientation-selective etching process, causing the formation of square opening pits. The CFx and C2 radicals induce the generation of the Si interface reactive layer, resulting in the occurrence of amorphous layers and termination of the non ⟨111⟩-crystal face in APE. The exciting O atoms preferentially occupy the active site of Si surfaces, causing the isotropic etching and then the formation of spherical opening pits. In addition, the richer O atoms will weaken the anisotropic etching ability of F atoms, resulting in the etched surface trends’ flattening. The insight into anisotropic etching behavior and topography formation mechanism of the silicon surface textured by atmospheric plasma is valuable for developing a new texturing approach to silicon solar cells.