Electron Cyclotron Resonance Microwave Research Articles

Mechanical and electrical properties of GeSb2Te4 film with external voltage applied

A GeSb2Te4 (GST) film was deposited by RF magnetron sputtering with microwave electron cyclotron resonance plasma chemical vapor deposition equipment. Mechanical and electrical properties together with the morphologies of the film were studied by a nanoindenter which was equipped with nano-electrical contact resistance (nano-ECR) tool and atomic force microscope (AFM). Results show that when no voltage applied between sample and indent tip during indenting, the pile-up phenomenon was observed, the hardness and elastic modulus increases with the load mainly due to the underestimate of the contact area; when external voltages of −7V, −8V, −9V, −10V were applied, the resistance of the film decreased with applied voltages in about four orders of magnitude, while the elastic modulus increased from 159GPa to 233GPa, this changing in mechanical and electrical properties demonstrated that phase change happen during intending, a shrinking region with radius of about 2.5μm was observed around the indentation when −8V applied. Furthermore, indent load can also promote the phase change at given negative voltage.

Improvement of SiO2/4H-SiC interface properties by electron cyclotron resonance microwave nitrogen-hydrogen mixed plasma post-oxidation annealing

We proposed an electron cyclotron resonance microwave nitrogen-hydrogen mixed plasma post-oxidation annealing process for SiO2/4H-SiC interface and investigated its effect on the electrical properties of the interface. The results indicate that this process could significantly reduce the density of interface traps (Dit) without degrading the oxide insulating properties. The best result is achieved for the 10-min annealed sample. The N and H, which are only concentrated at the SiO2/SiC interface, both play roles in reducing the Dit. N is more effective in passivating the shallow interface traps, while H is more effective in passivating the deep interface traps.

X-ray reflectivity study of bias graded diamond like carbon film synthesized by ECR plasma

Diamond like carbon (DLC) coatings were deposited on silicon substrates by microwave electron cyclotron resonance (ECR) plasma CVD process using plasma of Ar and CH 4 gases under the influence of negative d.c. self bias generated on the substrates by application of RF (13·56 MHz) power. The negative bias voltage was varied from −60 V to −150 V during deposition of DLC films on Si substrate. Detailed X-ray reflectivity (XRR) study was carried out to find out film properties like surface roughness, thickness and density of the films as a function of variation of negative bias voltage. The study shows that the DLC films constituted of composite layer i.e. the upper sub surface layer followed by denser bottom layer representing the bulk of the film. The upper layer is relatively thinner as compared to the bottom layer. The XRR study was an attempt to substantiate the sub-plantation model for DLC film growth.

Crystal AlN deposited at low temperature by magnetic field enhanced plasma assisted atomic layer deposition

In this paper, AlN films prepared at low temperature by magnetic field enhanced plasma assisted atomic layer deposition (PA-ALD) using trimethyl aluminum and the mixture gas of nitrogen and hydrogen were investigated. Two discharge modes were employed for PA-ALD AlN, i.e., radio-frequency (RF) discharge mode and microwave electron cyclotron resonance (ECR) mode. The structure of the film, compositions, crystallinity, surface roughness, and properties of refractive index as well as photoluminescence were studied by Fourier transform infrared spectroscope, x-ray photoelectron spectroscope, x-ray diffraction, atomic force microscope, spectroscopic ellipsometry, and photoluminescence spectrometer, respectively. Comparison of the as-deposited films prepared in two discharge modes, the authors result that temperature played an important role in in ECR mode, AlN films deposited in ECR mode at 250 °C is crystalline except a little bit of aluminum rich with the contamination of carbon and oxygen; whereas in RF discharge mode, the direct interaction of plasma, the all process parameters affect the properties of the AlN films, like the strength of magnetic field, deposition temperature. The intense emission band measured through photoluminescence spectrum of the as-deposited AlN suggests that there may be potential applications in electronic and optoelectronic nanodevices.

Study on the Distribution Control of Etching Rate and Critical Dimensions in Microwave Electron Cyclotron Resonance Plasmas for the Next Generation 450 mm Wafer Processing

A newly designed microwave electron cyclotron resonance (ECR) plasma etching reactor has been developed for 450 mm wafer processing. The etching rates of polycrystalline silicon (poly-Si) and SiO2 across the wafer were evaluated as a function of ECR position. Two-dimensional (radial and vertical) distributions of the ion flux in the reactor were also investigated using a movable single probe system. A ring-shaped region of high-density plasma along the ECR plane was observed. This reveals the mechanism that the etching-rate distribution could be controlled by the ECR position. As a result, a polycrystalline silicon etching rate uniformity of 1.5% across a wafer was successfully obtained. Furthermore, the uniformity control of critical dimensions (CDs) based on wafer temperature was also investigated, and CD uniformity below 3 nm across the wafer was obtained in the optimum temperature distribution.

Study on the Distribution Control of Etching Rate and Critical Dimensions in Microwave Electron Cyclotron Resonance Plasmas for the Next Generation 450 mm Wafer Processing

Study on the Distribution Control of Etching Rate and Critical Dimensions in Microwave Electron Cyclotron Resonance Plasmas for the Next Generation 450 mm Wafer Processing

Bias-independent growth of carbon nanowalls by microwave electron-cyclotron resonance plasma CVD

The investigations reported here describe the synthesis of carbon nanowalls (CNWs) by microwave electron-cyclotron resonance (ECR) plasma-assisted chemical vapour deposition (PACVD) process without an application of external bias to the substrate during growth. CNWs were grown on silicon (Si) substrates using hydrogen (H2)/methane (CH4) plasma at 650°C substrate temperature. Nickel (Ni) was used as a catalyst for the synthesis of CNWs. To the best of our knowledge, this is the first report that describes the bias-independent growth of CNWs using the ECR PACVD process. Formation of CNWs is confirmed by scanning electron microscopy and Raman spectroscopy. The discussion part also includes a possible growth mechanism for CNWs in terms of the role of surface plasmons.

Numerical analysis of a mixture of Ar/NH3 microwave plasma chemical vapor deposition reactor

A two-dimensional fluid model has been used to investigate the properties of plasma in Ar/NH3 microwave electron cyclotron resonance discharge at low pressure. The electromagnetic field model solved by the three-dimensional Simpson method is coupled to a fluid plasma model. The finite difference method was employed to discrete the governing equations. 40 species (neutrals, radicals, ions, and electrons) are consisted in the model. In total, 75 electron-neutral, 43 electron-ion, 167 neutral-neutral, 129 ion-neutral, 28 ion-ion, and 90 3-body reactions are used in the model. According to the simulation, the distribution of the densities of the considered plasma species has been showed and the mechanisms of their variations have been discussed. It is found that the main neutrals (Ar*, Ar**, NH3*, NH, H2, NH2, H, and N2) are present at high densities in Ar/NH3 microwave electron cyclotron resonance discharge when the mixing ratio of Ar/NH3 is 1:1 at 20 Pa. The density of NH is more than that of NH2 atom. And NH3+ are the most important ammonia ions. But the uniformity of the space distribution of NH3+ is lower than the other ammonia ions.

MoSx-Ta composite coatings on steel by d.c magnetron sputtering

Sputter-deposited MoS2 films have been often used as dry lubricant in various industrial fields, such as space application and much attention has been paid to reduction of friction coefficient and improvement of mechanical properties in recent decades. One way to achieve this is to deposit a MoS2 film doped with another metal. The MoSx-metal films were found to be denser, more adhesive and more oxidation-resistant than pure MoS2. In this study, MoSx-Ta composite films were synthesized by Electron Cyclotron Resonance microwave source enhanced DC sputtering with different target powers. The effects of doping Ta on mechanical properties of MoSx-Ta films were investigated. The morphology and structure of films were investigated using a scanning electron microscope (SEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). The microhardness was evaluated using microhardness test instrument, and the adhesion strengths were obtained using a scratch tester. The results showed that the S/Mo ratio was influenced by the dc sputtering target power. Typical MoS2 (100) (103) (002) orientations were present in pure MoSx films, but disappeared with the increase in doped Ta, with the S/Mo content ratios decreasing from 1.52 to 0.84, and the hardness increasing from 3.55 to 15.23 GPa. The roughness and surface topography, friction coefficient and adhesion were significantly affected by the Ta, Mo and S content. The content of doped Ta plays a dominant role on the change in the Mo/S ratio, thereby influencing the mechanical and tribological properties of the MoSx-Ta composite films.

Critical thickness and nanoporosity of TiO2 optical thin films

This work reports on the porosity and refraction index of TiO2 thin films as a function of the film thickness. Samples were fabricated by plasma enhanced chemical vapor deposition (PECVD) in a microwave electron cyclotron resonance (MW-ECR) reactor at room temperature using titanium tetra-isopropoxide (TTIP) as precursor. Experimental parameters such as plasma gas composition (pure oxygen and argon/oxygen mixtures) and pressure (either ECR conditions or “normal” pressure, i.e. 10−4 or 10−3torrs correspondently) were varied. The evolution of the thin film microstructure, porosity and optical properties is critically studied by AFM, SEM, water adsorption isotherms, ellipsometry and UV–Vis transmittance and the existence of a certain critical thickness (tc) demonstrated. The porosity of the films with thicknesses ranging from several tens of nanometers up to half a micrometer is evaluated by QCM-isotherms at room temperature. The dependency of this critical thickness with the plasma conditions is evaluated experimental and theoretically. Thus, the microstructure change at tc is attributed to a transition from a surface diffused dominated growth mechanism for t<tc to another where shadowing is predominant. Dynamic scaling analysis of the two regimes and their Monte Carlo simulation complete the reported study.

Low temperature preparation of transparent, antireflective TiO2 films deposited at different O2/Ar ratios by microwave electron cyclotron resonance magnetron sputtering

A serial of crystalline titanium oxide ceramic films were deposited at low temperature using microwave electron cyclotron resonance (MW-ECR) magnetron sputtering with different O2/Ar ratios. The influences of O2/Ar ratio on the deposition rate, morphology, crystalline nature, optical adsorption property of the obtained titanium oxide thin films were investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM) and UV–Vis spectra. Therefore, the optimum O2/Ar ratio for deposition of anatase TiO2 thin films on unheated glass substrate was realized in a MW-ECR magnetron sputtering process. The as-deposited anatase TiO2 films were transparent and were antireflective in the visible region.

Preparation and characterization of multilayered titanium/titanium-diamond-like carbon films

The titanium/titanium diamond-like carbon (Ti/Ti-DLC) multi-layered films are deposited by combined electron cyclotron resonance microwave plasma enhanced chemical vapor deposition method and mid-frequency magnetron sputtering method using acetylene as the reactive gas and Ti target with a purity of 99.99%. The structures, compositions and surface morphologies of the samples are characterized by X-ray diffraction, scanning electron microscope, and X-ray photoelectron spectrometer. The mechanical properties of Ti/Ti-DLC multilayer films are investigated by microhardness tester, friction wear test instrument and surface roughmeter. The results show that TiC phase appears in multilayered film. The main growth mode of the film is island mode and there exists columnar crystal structure neither in Ti layer nor Ti-DLC layer. The properties of the multi-layered film, including composite hardness, friction coefficient, surface morphology and surface roughness are affected by the modulation period . It is shown that nano-hardening effect takes place when is small while large particles appear on the surface of the film, leading to a large surface roughness and friction coefficient. The layered structure of the film is not clear when 50 nm.

Reactive expansion of laser-induced boron/carbon plasma in ECR nitrogen plasma during the deposition of BCN films

The expansion of the boron/carbon plasma induced by pulsed laser ablation of B 4C in the nitrogen plasma generated by electron cyclotron resonance (ECR) microwave discharge of N 2 gas was studied by optical emission spectroscopy (OES). OES measurements show that at the initial stages the mono-atomic species ablated from B 4C are the dominant emitting species and after 0.5 μs the plasma emission evolves to be dominated by the emission bands from nitrogen molecules and nitrogen molecular ions, revealing that the N 2 gas is highly excited by the hybrid processes of ECR microwave discharge and pulsed laser ablation. In addition to the emissions emitted from the species ablated from the target and present in the reactive background, C 2 and CN emissions are also observed. The characteristics of the emissions from various species provide an access to the reactive expansion of the boron/carbon plasma in the nitrogen plasma and the gas-phase reactions occurring in the plasmas during the deposition of BCN films by nitrogen plasma assisted pulsed laser deposition. The mechanisms for efficient incorporation of nitrogen in the films were also discussed.

Spectroscopic Characterization of Plasmas Generated by ECR Microwave Discharge of N2 Gas and Pulsed Laser Ablation of a B4C Target

AbstractThe plasmas generated by co‐action of electron cyclotron resonance (ECR) microwave discharge of N2 gas and pulsed laser ablation (PLA) of a B4C target were spectroscopically characterized using time‐ and space‐resolved optical emission spectroscopy (OES). The plasmas exhibit rapid variations in time and space and the optical emissions of the plasmas show unique characteristics in comparison with the plasmas generated solely by ECR discharge or PLA. At the early stages of the expansion of the PLA boron/carbon plasma in the ECR nitrogen plasma, the plasma emission is dominated by emission lines from atomic and ionic boron and carbon which decrease rapidly during the expansion of the PLA plasma, and then evolves to be dominant in emission bands from nitrogen molecules and nitrogen molecular ions. The emission bands of the C2 Swan system and the CN violet system were also distinguished. The processes including gas‐phase reactions occurring in the plasmas were discussed based on the characteristics of the plasma emissions.magnified image

Silicon nitride gradient film as the underlayer of ultra-thin tetrahedral amorphous carbon overcoat for magnetic recording slider

There are higher technical requirements for protection overcoat of magnetic recording slider used in high-density storage fields for the future. In this study, silicon nitride (Si-N) composition-gradient films were firstly prepared by nitriding of silicon thin films pre-sputtered on silicon wafers and magnetic recording sliders, using microwave electron cyclotron resonance plasma source. The ultra-thin tetrahedral amorphous carbon films were then deposited on the Si-N films by filtered cathodic vacuum arc method. Compared with amorphous carbon overcoats with conventional silicon underlayers, the overcoats with Si-N underlayers obtained by plasma nitriding especially at the substrate bias of −150 V, can provide better corrosion protection for high-density magnetic recording sliders.

Microwave ECR Plasma Assisted MOCVD of Y2O3 Thin Films Using Y(tod)3 Precursor and Their Characterization

AbstractYttrium oxide (Y2O3) thin films were deposited by microwave electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapour deposition (MOCVD) process using indigenously developed metal organic precursors Yttrium 2,7,7‐trimethyl‐3,5‐octanedionates, commonly known as Y(tod)3 which were synthesized by an ultrasound method. A series of thin films were deposited by varying the oxygen flow rate from 1–9 sccm, keeping all other parameters constant. The deposited coatings were characterized by X‐ray photoelectron spectroscopy, glancing angle X‐ray diffraction and infrared spectroscopy. Thickness and roughness for the films were measured by stylus profilometry. Optical properties of the coatings were studied by the spectroscopic ellipsometry. Hardness and elastic modulus of the films were measured by nanoindentation technique. Being that microwave ECR CVD process is operating‐pressure‐sensitive, optimum oxygen activity is very essential for a fixed flow rate of precursor, in order to get a single phase cubic yttrium oxide in the films. To the best of our knowledge, this is the first effort that describes the use of Y(tod)3 precursor for deposition of Y2O3 films using plasma assisted CVD process. magnified image

Tribological Properties of Hydrogenated Amorphous Carbon (a-C:H) Films on Aluminium Alloy Substrate under Different Substrate Bias Voltages

Hydrogenated amorphous carbon (a-C:H) films were deposited on aluminium alloy substrates by microwave electron cyclotron resonance chemical vapor deposition(ECR-PECVD) at different substrate pulse bias voltage. In order to enhance the interface bonding strength between the film and Al alloy substrate, a 50nm silicon film was firstly fabricated on aluminium alloy substrate by unbalanced magnetron sputtering. The fiction and wear properties of the a-C:H films were evaluated using a ball-on-disk tribometer in air at room temperature. The results showed that the tribological properties of the a-C:H films decreased with the substrate bias voltage increased from -150 to -1000V. The a-C:H films deposited at -150V bias voltage had the best wear resistance.

Measurement of Ion Parameters by Ion Sensitive Probe in ECR Plasma

Ion parameters in electron cyclotron resonance (ECR) microwave plasma were measured by ion sensitive probe and were compared with the electron parameters obtained by double Langmuir probe. The effects of gas pressure and microwave power on the ion temperature and density were analyzed. The spatial distribution of the ion parameters was also investigated by the ion sensitive probes with a tunable radial depth installed on different probe windows along the chamber axis. Results showed that the ion density measured by the ion sensitive probe was in good agreement with the electron density measured by the double Langmuir probe. The influence of gas pressure on the ion parameters was stronger than that of microwave power. With the increase in working pressure, the ion temperature decreased monotonously with a decreasing rate larger than that at higher pressure. The ion density first increased to a peak (42.3×1010 cm-3) at 1 Pa and then decreased. The ion temperature and density increased little with the increase in the microwave power from 400 W to 800 W. The plasma far away from the resonant point is found to be radially uniform.

Effects of precursor evaporation temperature on the properties of the yttrium oxide thin films deposited by microwave electron cyclotron resonance plasma assisted metal organic chemical vapor deposition

Yttrium oxide thin films are deposited using indigenously developed metal organic precursor (2,2,6,6-tetra methyl-3,5-hepitane dionate) yttrium, commonly known as Y(thd) 3 (synthesized by ultrasound method). Microwave electron cyclotron resonance plasma assisted metal organic chemical vapor deposition process was used for these depositions. Depositions were carried out at a substrate temperature of 350 °C with argon to oxygen gas flow rates fixed to 1 sccm and 10 sccm respectively throughout the experiments. The precursor evaporation temperature (precursor temperature) was varied over a range of 170–275 °C keeping all other parameters constant. The deposited coatings are characterized by X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and infrared spectroscopy. Thickness and refractive index of the coatings are measured by the spectroscopic ellipsometry. Hardness and elastic modulus of the films are measured by load depth sensing nanoindentation technique. C-Y 2O 3 phase is deposited at lower precursor temperature (170 °C). At higher temperature (220 °C) cubic yttrium oxide is deposited with yttrium hydroxide carbonate as a minor phase. When the temperature of the precursor increased (275 °C) further, hexagonal Y 2O 3 with some multiphase structure including body centered cubic yttria and yttrium silicate is observed in the deposited film. The properties of the films drastically change with these structural transitions. These changes in the film properties are correlated here with the precursor evaporation characteristics obtained at low pressures.

The mechanical properties of the ultrahigh molecular weight polyethylene (UHMWPE) modified by oxygen plasma

In this work, ultrahigh molecular weight polyethylene (UHMWPE) was modified with oxygen plasma generated by microwave electron cyclotron resonance (ECR). Surface microstructure and properties of UHMWPE were studied by means of water contact angle measurement, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy, scratch test and wear test. The results showed that O 2 plasma treatment could effectively improve the wettability, anti-scratch and tribological properties of UHMWPE. Many oxygen-based functional groups generated on the surface of the O 2 plasma modified UHMWPE, which resulted in the improvement of wettability. The plasma treatment process increased the crosslinking of UHMWPE molecular chains, which further enhanced the action force between the molecular chains and finally increased the surface hardness, anti-scratch capacity and tribological properties of UHMWPE.