Ar Plasma Research Articles

Effect of Ar and N2 plasma etching on adhesion between mold resin and sputtered Cu in semiconductor electromagnetic shielding

In recent years, there has been growing demand for processes to form electromagnetic shielding films on the periphery of semiconductor packages, and shielding films are increasingly being formed by sputter deposition methods with stable processes. However, little consideration has been given to the adhesion mechanism between the mold resin and sputtered Cu film formed on the semiconductor devices. In this study, Cu films were sputtered on mold resin with different etching conditions, and X-ray photoelectron spectroscopy was used to analyze the state of the interface, which affects adhesion. The color difference of the mold resin surface under different Ar and N2 etching conditions was also evaluated. Excellent adhesion between the mold resin and sputtered Cu was achieved under a high flow rate for Ar + N2 etching. The amount of Si (SiO2) exposed on the mold resin surface was correlated with the color difference. We proposed a mechanism in which amino groups in particular were formed on the surface of the mold resin, the resin etching rate increased, and the amount of SiO2 exposed increased. Functional groups, especially amino groups, were also formed on the SiO2 surface by N2 plasma. Cuσ+ in the sputtered film and Nσ- formed on the SiO2 surface adhered to each other through polar interactions.

Influence of Terbium Doping and Annealing on the Structural and Optical Characteristics of Sputtered Zinc Oxide Thin Films

This paper studied the structural and luminescent characteristics of undoped and doped-with-Tb3+-ions ZnO films of 200 nm and 600 nm thicknesses, grown via RF magnetron sputtering on (100) silicon substrate in Ar and Ar-O2 plasma. X-ray diffraction (XRD) patterns revealed a strong preferred orientation of ZnO and ZnO:Tb crystals of the wurtzite structure along the c-axis, perpendicular to the substrate. In the as-deposited ZnO:Tb films, the additional crystal phases, namely, Tb2O3, TbO2, and an amorphous phase, were revealed. The as-deposited undoped films were under tensile strain, that increased in the doped films. This proved the incorporation of the Tb3+ ions into the ZnO grains, and agreed with the Raman spectra investigation. The XRD data and atomic force microscopy study showed that Tb doping impeded the growth of grains and columns, respectively. The photoluminescence (PL) spectra of the doped films contained the UV band ascribed to exciton PL, a broad intrinsic defect-related band, and the narrow bands caused by the intra-shell transitions of the Tb3+ ions. Terbium doping suppressed ZnO emissions. The post-deposition rapid thermal annealing at up to 800 °C of both the undoped and doped films promoted tensile strain relaxation, grain growth, improvement in the ZnO crystal structure, and an increase in the exciton PL. The intensity of the Tb3+ PL changed non-monotonically, and was the highest for the film annealed at 600 °C. The conventional thermal annealing promoted the non-monotonic changes in the strains and grain sizes in such a way that, after annealing at 900 °C, their values became the same as in the as-deposited ZnO:Tb film. This structural change was accompanied by a decrease in the exciton and Tb3+ PL intensity. The formation of the Zn2SiO4 phase was observed via XRD, and confirmed via scanning electron microscopy. It was attributed to the interdiffusion through the film/substrate interface. The deposition in the Ar-O2 atmosphere is found to be more preferable for the formation of Tb3+ emission centers in the ZnO matrix.

Radial dependence diagnosis of inductively coupled Ar plasma based upon optical emission spectroscopic measurement with spectral reflectance compensation

This study proposed a simple method to evaluate the spectral reflectance of the inner wall of a vacuum chamber. A method for calculating spectral emission coefficients by taking the spectral reflectance of the chamber inner wall into account was proposed. Furthermore, plasma diagnosis based on optical emission spectroscopic (OES) measurement was performed so as to obtain radial dependence of electron temperature Te and density Ne of a radio frequency inductively coupled Argon (Ar) plasma by applying a collisional-radiative model to radially resolved emission spectra of the Ar plasma assuming axial symmetry. In addition, Langmuir probe measurement and electromagnetic simulation were performed and compared with the OES-based plasma diagnosis results. The spectral radiance compensation improved the diagnostic result by 0.6% and 3.1% for Te and Ne, respectively.

Plasma-engineered Mo2C catalysts for high-activity hydrogen evolution reaction

As a typical hard alloy, Mo2C attracted most researchers’ interests for excellent mechanical stability, which reveals great potentials as robust electrocatalysts. However, the deviation of Mo2C catalytic adsorption and desorption energy from the volcano curve center hinders its catalytic efficiency, and the robust lattice structure of Mo2C poses a significant challenge to conventional modification approaches aimed at improving its catalytic properties. In current study, Ar plasma etched Mo2C nanofibers (Ar–Mo2C) were successfully fabricated which exhibits significantly higher HER activity with an overpotential of 151 mV and a Tafel slope of 29 mV dec−1. Ar etching can create Mo and C vacancies to enhance the charge transfer capability. Current work paves an efficient way for surface processing of hard alloys for high electrocatalytic activity, which inspires future robust nanoelectrocatalysts design.

Enhancement of S-scheme heterojunction hematite and titanium dioxide nanocomposite by plasma treatment in the photocatalytic membrane for hydrogen separation

This work evaluated the performance of the photocatalytic membrane reactor (PMR) for hydrogen and oxygen separation. The PMR was conducted in a 500-ml reactor under solar light simulated by a mercury arc lamp (250 W). Hematite (α-Fe2O3) was deposited on titanium dioxide (TiO2) by sol-gel method on the Ti foil while palladium (Pd) was deposited on the other side. The sample surface was modified by argon (Ar) gas plasma treatment at 50 W for 10 min. The S-scheme heterojunction photocatalyst was characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, and UV–vis spectroscopy. The charge carrier transport of photocatalysts was also analyzed. The photocatalytic activity was significantly improved by plasma treatment. The band gap energy decreased from 1.88 eV to 1.77 eV, and the average crystalline was reduced from 21.62 ± 4.79 nm to 21.34 ± 5.63 nm. The photocatalytic activity of fabricated materials for hydrogen production was evaluated in multi-cycle experiments. The highest hydrogen production rate of 1346.19 µmol h−1 was observed for the Ar plasma-treated heterojunction α-Fe2O3 and TiO2 nanocomposite sample (α-Fe2O3 @TiO2-P). After 5 cycles, the photocatalyst reaction of α-Fe2O3 @TiO2-P under solar light irradiation showed high stability for H2 production of 85.24 % compared to the first cycle. The S-scheme was photogenerated of charge transferred of type S-scheme mechanism between α-Fe2O3 and TiO2 under solar light. This work provides insight to enhance hydrogen production through the modification of the S-scheme photocatalyst membrane. The improved photocatalytic performance of the fabricated material suggests the effectiveness of the proposed Ar plasma treatment strategy to enhance the photoactivity for H2 production via water splitting.

Surface modification of polyethylene using argon and argon/methane DBD atmospheric pressure plasma jet

This article investigates the surface modification of polyethylene (PE) using an atmospheric pressure plasma jet of the DBD type (APPJ) maintained with pure argon (Ar) and with a premixed gas containing 90% argon and 10% of CH4. First and for both plasma jets, the jet length and the optical emissions coming from the plasma species were studied in terms of flow rate and applied voltage. Comparing to Ar, it has been shown that when the premixed gas is used, the jet length gets smaller, the transition point from laminar to turbulent regime was shifted to a low flow rate, and the emission of CH, H2 and C2 appeared, while O and N2 emission coming from ambient air was quenching. The PE surface treatment in both laminar and turbulent regime has been evaluated using water contact angle (WCA) measurement and attenuated total reflection (ATR). The obtained results showed that the hydrophilicity of PE has been improved in both plasma jets due to oxygen group (C=O) incorporation, but Ar plasma jet was observed to induce surface degradation compared to Ar/CH4 plasma due to the higher excited species.

Effect of Er: YAG laser and plasma treatment on the bond strength of Y-TZP

ObjectivesThis study aimed to evaluate the effects of Er:YAG laser and plasma treatment on the bond strength between Y-TZP and resin cement. Materials and methodsSixty yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) specimens were fabricated and randomly assigned to six groups (n = 10): control group (group A); Sandblasting treatment (group B); Er:YAG laser group (group C); Ar plasma group (group D); Sandblasting + Ar plasma group (group E); and Er:YAG laser + Ar plasma group (group F). The surface of each zirconia specimen was tested using a contact angle meter, profilometer, and scanning electron microscope, and the shear bonding strength (SBS) was calculated. Statistical analysis was performed with One-way analysis of variance (ANOVA) combined with a least significant difference (LSD) test. ResultsThe surface morphology showed no difference between group A and group D, with smooth surfaces and shallow scratches after polishing. The surface roughness value of group C was 2.58 ± 0.14μm and was not significantly different from that of group F (P > 0.05), was higher than that of group A (P < 0.05). The SBS of group B was not significantly different from that of group D (P > 0.05). The hydrophilicity, carbon and oxygen contents, and SBS of group E were similar to those of group F (P > 0.05) and significantly higher than those of groups A, B, C, and D (P < 0.05). SignificanceThe Er:YAG laser and Ar plasma treatment can improve the bonding strength between zirconia and resin cement, and mechanical treatment followed by Ar plasma surface modification is more effective.

Toolbox of Advanced Atomic Layer Deposition Processes for Tailoring Large-Area MoS2 Thin Films at 150 °C.

Two-dimensional MoS2 is a promising material for applications, including electronics and electrocatalysis. However, scalable methods capable of depositing MoS2 at low temperatures are scarce. Herein, we present a toolbox of advanced plasma-enhanced atomic layer deposition (ALD) processes, producing wafer-scale polycrystalline MoS2 films of accurately controlled thickness. Our ALD processes are based on two individually controlled plasma exposures, one optimized for deposition and the other for modification. In this way, film properties can be tailored toward different applications at a very low deposition temperature of 150 °C. For the modification step, either H2 or Ar plasma can be used to combat excess sulfur incorporation and crystallize the films. Using H2 plasma, a higher degree of crystallinity compared with other reported low-temperature processes is achieved. Applying H2 plasma steps periodically instead of every ALD cycle allows for control of the morphology and enables deposition of smooth, polycrystalline MoS2 films. Using an Ar plasma instead, more disordered MoS2 films are deposited, which show promise for the electrochemical hydrogen evolution reaction. For electronics, our processes enable control of the carrier density from 6 × 1016 to 2 × 1021 cm-3 with Hall mobilities up to 0.3 cm2 V-1 s-1. The process toolbox forms a basis for rational design of low-temperature transition metal dichalcogenide deposition processes compatible with a range of substrates and applications.

Influence of Si(111) substrate off-cut on AlN film crystallinity grown by magnetron sputter epitaxy

The increasing demand for More than Moore devices requires epitaxy technology to keep up with the discovery and deployment of new semiconductors. An emerging technology for cost-effective, device-quality growth is magnetron sputter epitaxy, though detailed studies on the process itself remain scarce. Here, we report an extensive study on the correlation between the substrate off-cut and film quality in AlN-on-Si heteroepitaxy. Controlled reactive pulsed magnetron sputtering is used to grow epitaxial AlN(0001) films on in situ Ar plasma etched off-cut Si(111) substrates with growth rates above 1.5 nm/s. Substrate off-cut angles in the range of 0.02°–0.30° are investigated and precisely determined by high-resolution x-ray diffraction. Structural examination of the AlN films is carried out by transmission electron microscopy and high-resolution x-ray diffraction. The AlN/Si interface is well-defined and two types of AlN domains with epitaxial relationships are observed. The formation of secondary rotation domains deteriorates the crystal quality substantially. Substrates with small off-cuts, ideally no off-cut substrates, appear to be crucial for suppressing the formation of secondary domains and further result in a better overall crystal quality of AlN films. We discuss this effect in relation to the AlN/Si interface, the substrate pre-treatment, and nucleation.

Unraveling Exclusive In-Plasma Initiated Oxidation Processes Occurring at Polymeric Surfaces upon O2 Admixtures to Medium Pressure Ar and N2 DBD Treatments.

Polymeric surfaces have been increasingly plasma-activated to adopt adequate chemistries, enabling their use in different applications. An unavoidable surface oxygen insertion upon exposure to non-oxygen-containing plasmas was always observed and mainly attributed to in-plasma oxidation stemming from O2 impurities in plasma reactors. Therefore, this work investigates exclusive in-plasma oxidation processes occurring on polyethylene surfaces by purposely admixing different O2 concentrations to medium-pressure Ar and N2 dielectric barrier discharges (base pressure: 10-7 kPa). Hence, distinctive optical emission spectroscopy and in-situ X-ray photoelectron spectroscopy (XPS) data were carefully correlated. Pure N2 discharge triggered an unprecedented surface incorporation of large nitrogen (29%) and low oxygen (3%) amounts. A steep rise in the O-content (10%) at the expense of nitrogen (15%) was detected upon the addition of 6.2 × 10-3% of O2 to the feed gas. When the added O2 exceeded 1%, the N content was completely quenched. Around 8% of surface oxygen was detected in Ar plasma due to high-energy Ar metastables creating more surface radicals that reacted with O2 impurities. When adding only 6.2 × 10-3% of O2 to Ar, the surface O content considerably increased to 12%. Overall, in-plasma oxidation caused by O2 impurities can strikingly change the surface chemistry of N2 and Ar plasma-treated polymers.

Enhancing surface adhesion of polytetrafluoroethylene induced by two-step in-situ treatment with radiofrequency capacitively coupled Ar/Ar+CH4+NH3 plasma

Although some progress in plasma modification of the polytetrafluoroethylene (PTFE) surface has been made recently, its adhesion strength still needs to be further improved. In this work, the surface of a PTFE sample was treated with a two-step in-situ method. Firstly, the PTFE surface was treated with capacitively coupled Ar plasma to improve its mechanical interlocking performance; then, Ar+NH3+CH4 plasma was used to deposit an a-CN x :H cross-linking layer on the PTFE surface to improve the molecular bonding ability. After treatment, a high specific surface area of 2.20 and a low F/C ratio of 0.32 were achieved on the PTFE surface. Its surface free energy was increased significantly and its maximum adhesion strength reached 77.1 N·10 mm−1, which is 56% higher than that of the single-step Ar plasma-treated sample and 32% higher than that of the single-step Ar+CH4+NH3 plasma-treated sample.

Bias-supply timing tailored to the aspect ratio dependence of silicon trench etching in Ar plasma with alternately injected C4F8 and SF6

In semiconductor device fabrication, the feature profiles of a high-aspect-ratio (HAR) Si trench is needed to be controlled considering aspect-ratio-dependent etching (ARDE). This is achieved by a cyclic process in which Ar plasma is sustained while C4F8 and SF6 are alternately injected and a short-period supply of a substrate bias is provided. Presently, the transient behaviors of gaseous and surface reactions are dynamically revealed by measuring the plasma parameters using a surface wave probe and optical emission spectroscopy. When the etched surface is fluorinated during the cycle, an ARDE-free Si-trench feature profile can be fabricated by controlling the bias-supply timing.

Performance improvement of MOCVD grown ZnGa2O4 based NO gas sensors using plasma surface treatment

Gas sensors are essential devices in various industrial and environmental monitoring applications. Nitric oxide (NO) is a harmful gas that is produced in various combustion processes and is associated with air pollution and respiratory diseases. Zinc gallate (ZnGa2O4) has shown promising results as a material for NO gas sensing applications. Previously, the performance of NO gas sensors based on ZnGa2O4 epilayers was not substantial. However, there is potential for further improvement by optimizing their surface properties. Plasma surface treatment has been widely utilized to modify the surface characteristics of materials, including semiconductors, for various applications. We have investigated the impact of plasma surface treatment on the performance of metal–organic chemical vapor deposition grown ZnGa2O4 based NO gas sensors in this work. An inductive coupled plasma reactive ion etching was used to apply Ar plasma to successfully optimize the sensing response of the ZnGa2O4 based gas sensor for NO gas. The sensor response for ZnGa2O4-based NO gas sensors is 159.5%, which is enhanced by 8 times and reached 1276.1% under 5 ppm NO gas concentration after 10 min Ar plasma treatment. The limit of detection is found to be 2.4 ppb. These results demonstrate that Ar plasma treatment significantly improved the ZnGa2O4-based NO gas sensor’s response. The cross-selectivity of this sensor is tested among NO, CO2, CO, and SO2 gases, which indicated that ZnGa2O4 gas sensor possess highly selectivity towards NO gas. This study provides valuable insights into the surface modification techniques for enhancing the performance of gas sensors, which can have a significant impact on the development of advanced sensing technologies for environmental and industrial applications.

Two-Step Cyclic Etching of Copper Thin Films Using Acetylacetone/O2 Gases

Two-step cyclic etching of copper thin films was carried out using acetylacetone/O2 gases and Ar plasma. The copper film surfaces were first modified by exposing them to acetylacetone/O2 gases and the modified layers were removed via Ar-ion sputtering. The surface modification step was optimized by varying the flow rate of the acetylacetone/O2 gases and exposure time. The removal step was optimized by varying the dc-bias voltage to the substrate as well as sputtering time. The surface modification and removal of the modified layers were confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The etch per cycle was estimated to be in the range of 0.7–3.0 nm. The cyclic etching of the copper films using acetylacetone/O2 gases and Ar sputtering revealed good etch profiles with an etch slope of 70° without redepositions. It is proposed that the cyclic etching using acetylacetone/O2 gases and Ar can be a suitable method to delineate the fine patterns on copper films.

Interaction of a precursor soliton with wake structure in a flowing dusty plasma

We report experimental observations on the interaction of a precursor soliton with a wake structure in a flowing dusty plasma system. The experiments are carried out in an inverted ∏-shaped experimental device in which a dusty plasma is created in a direct current glow discharge Ar plasma using micrometer sized Kaolin particles. Two copper wires installed radially on the cathode serve as charged objects in the plasma environment. Precursor solitons and wake structures are excited by each of the charged objects when the dust fluid flows supersonically over both the objects. In the frame of the fluid, the solitons propagate in the upstream direction, whereas the smaller amplitude wake structures propagate in the downstream direction. A soliton, excited by one of the objects, interacts with the wake structure generated by the other object in the region between the two charged objects. After the interaction, the amplitude and velocity of the soliton increase whereas its width decreases. The results are explained theoretically using numerical solutions of a model forced Korteweg-de Vries equation driven by two source terms.

An Evaluation of the Usability of Argon Plasma-Treated Bacterial Cellulose as a Carrier for Controlled Releases of Glycoside Hydrolases PelAh and PslGh, Which Are Able to Eradicate Biofilm

Bacterial cellulose is a unique biopolymer that has found numerous biomedical applications, such as being an excellent wound-dressing material or a carrier for delivering active compounds. The purpose of this study was to analyze the ability of modified bacterial cellulose (BC) using low-pressure Ar plasma to control the release of glycoside hydrolases with antibiofilm activity, namely PelAh and PslGh, from Pseudomonas aeruginosa. The chemical composition and morphology of the BC surfaces were characterized using photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The analyses revealed significant changes in the chemical composition of the BC surface due to the introduction of charged functional groups and the conversion of its well-ordered structure into a more amorphous form. The release profiles of enzymes from both forms of the carrier were different and depended on their structural properties. However, a significant impact of BC modification on protein release behavior from the carrier was observed only for PslGh. Both enzymes, when immobilized on pristine and argon plasma-modified BC, retained their ability to effectively reduce biofilm levels, similarly to their soluble form. Ar plasma-modified BC with immobilized specific hydrolases can be used as an effective tool for inhibiting P. aeruginosa biofilm development.

Highly response gas sensor based the Au-ZnO films processed by combining magnetron sputtering and Ar plasma treatment

The excellent and promising gas sensors not only have high response, but also can be easily integrated with other semiconductor devices to form an intelligent chip. In order to realize this goal, an effective strategy is proposed to combine the magnetron sputtering and Ar plasma treatment. As a result, a high-performance sensor based on Au-ZnO films is achieved at the optimal technology parameter, with high response (Ra/Rg) of 190 to 100 ppm isopropanol (IPA), rapid response/recovery speed of 1 s/18 s, and low detection limit of 100 ppb at 300 °C. Moreover, the mechanisms of the improvement on the sensing properties of the as-fabricated sensor are discussed. The present work provides new ideas for the future development of integrating gas sensors with functional circuits to form a smart chip that can perform data acquisition, processing and storage.

Etching characteristics and surface modification of InGaSnO thin films under Cl2/Ar plasma

Indium gallium tin oxide (IGTO) thin films have the potential for high mobility and low-temperature processing, which makes them suitable for applications such as display backplanes and high-voltage switching devices. However, very few studies have investigated the plasma-etching characteristics of IGTO and changes in its properties after etching. In this study, the etching characteristics of IGTO were investigated using Cl2/Ar plasma, and changes in surface properties were analyzed. Results showed that the etch rate increased with an increase in the proportion of Cl2, with the highest etch rate observed at 69 nm min−1 in pure Cl2 plasma with a gas flow rate of 100 sccm. Furthermore, increased radio-frequency power caused a rise in the etch rate, while a process pressure of 15 mTorr was optimal. The primary etching mechanism for IGTO thin films under Cl2 plasma was a chemical reaction, and an increased work function indicated the occurrence of defects on the surface. In addition, the etching process reduced the surface roughness of Cl2-containing plasma, whereas the etching process in pure Ar plasma increased surface roughness. This study contributes to a better understanding of the plasma-etching characteristics of IGTO and changes in its properties after etching, providing valuable insights for IGTO-based applications.

Low temperature Cu/SiO2 hybrid bonding via 〈1 1 1〉-oriented nanotwinned Cu with Ar plasma surface modification

Argon (Ar) plasma surface modification and highly (111)-oriented nanotwinned copper (nt-Cu) were combined to lower the bonding temperature of Cu/SiO2 hybrid joints. The contact angle of water on SiO2 could be reduced from 22.6° to 3.3° after the plasma treatment. Benefiting from the high surface diffusivity of nt-Cu and great hydrophilicity of the plasma-assisted SiO2, the bonding temperature could be reduced to 150 ℃. However, such a plasma treatment caused the serious oxidation of the activated Cu in the ambient. To balance the activation and oxidation of the Cu films, Ar plasma power was tuned. X-ray photoelectron spectroscopy (XPS) was used to analyze the SiO2 surfaces. We found an increase (13.6% to 28.3%) in Si-OH and decreases in Si-O and C-O intensities after the plasma activation. Such decreases in Si-O and C-O intensities could be attributed to the removal of organic compounds. Shear tests were also conducted to characterize the bonding strength of the joints. An excellent bonding strength > 35 MPa was achieved after the post annealing and plasma treatment.

High-throughput SiN ALE: surface reaction and ion-induced damage generation mechanisms

Atomic layer etching (ALE) has been practically implemented as a technique to achieve atomic/molecular level control. However, its main disadvantage is that it involves long process time. The surface reaction mechanism required to realize high-throughput (HT) SiN ALE was investigated. CH3F/Ar plasma was applied in the adsorption step, while Ar plasma was used in the desorption step. Finally, an additional O2 ashing step was applied. To reduce process time, HT ALE was performed at high ion energy, and the amount of etched SiN was evaluated. HT SiN ALE conducted at short time intervals and at high ion energy underwent a quasi-self-limited reaction, which is a characteristic of ALE, and the process time decreased. However, HT ALE using CH3F in the adsorption step caused an increase in the extent of the damage. Thus, the use of C4F8 (without H) can significantly reduce damage even under HT ALE conditions.