Studies of medium frequency high power density magnetron sputtering discharges

Optical emission spectroscopy and Langmuir probe have been used to study the power dependence of medium frequency, 100 kHz, pulsed magnetron sputtering discharge. Copper target was sputtered in the argon atmosphere. The examined power ranged from 0.5 to 4.5 kW which gave an average power density on target surface from 25 to 115 W/cm². Optical spectroscopy did not reveal any significant changes of copper ion contribution to the sputtering process. The electron temperature and plasma potential changed a little with applied power. The electron density depended linearly on the sputtering power.     

Characterization by optical emission spectroscopy of an oxygen plasma used for improving PET wettability

Polymers have excellent bulk physical and chemical properties but usually poor surface properties. For wettability improvement plasma technology is one of the most promising techniques. Several studies about surface modifications of polyethylene terephthalate (PET) exposed to an oxygen plasma have been already carried out. In this work an analysis of the plasma phase by optical emission spectroscopy (OES) has been employed in order to establish a correlation with the surface effects induced by plasma exposition on PET chemical composition and wettability, investigated by X-ray photoelectron spectroscopy (XPS) and water contact angle measurements, respectively. The treatment has been carried out for a time of 60 s at a constant pressure (15 Pa) and at different process powers ranging from 20 to 200 W. As expected, the best performance has been obtained at a power of 200 W due to the larger presence of oxygen radicals (OI) with the assistance of ionic species (OII, O₂⁺) which create dangling bonds on the substrate surface.     

Effect of deflection on the mechanical and optoelectronic properties of indium tin oxide films deposited on polyethylene terephthalate substrates by pulse magnetron sputtering

In this research, we studied the effect of deflection on the characteristics of an indium tin oxide (ITO) film deposited on a flexible polyethylene terephthalate flexible substrate by pulse magnetron sputtering. The experimental results show that an increase in the ITO film thickness leads to an increase in the residual stress and a decrease in the adhesion. Under power of 80 W, pulse frequency of 10 kHz, pulse reverse time of 2 μs, and ITO film thickness of 100 nm, thin film with an optimized resistivity of 4.5 × 10^− 4 Ω-cm, visible light transmittance of more than 84%, and adhesion of class 5B/0 as per the ASTM/ISO standards. Micro-cracking was observed on the ITO film surface when the film thickness was greater than 100 nm and when the deflection was carried out for 100 times. Micro-cracking led to an increase in the residual stress and deterioration in the adhesion properties.     

Experimental investigations of semi-crystalline plasma polymerized poly(3-octyl thiophene)

Plasma polymerized thin film of conducting poly(3-octylthiophene) was deposited at room temperature by plasma enhanced chemical vapor deposition method using (3-octylthiophene) monomer as precursor. The radio frequency (RF: 13.56 MHz, power supply: 30 W) was applied at constant argon gas pressure for the formation of plasma. Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), X-ray diffractometry (XRD) and high resolution transmission electron microscopy (HRTEM) have been done for the as grown films. As reported in literature polythiophenes prepared by rf plasma polymerization are highly crosslinked and amorphous. However, in present investigations, well defined crystalline regions have been observed by HRTEM investigations and have been correlated with X-ray diffraction data. The observed crystallinity is attributed to controlling the parameters of the synthesis.     

Synthesis of ultra-smooth and ultra-low friction DLC based nanocomposite films on rough substrates

Rough TiC/a-C films were intentionally grown on smooth surface to simulate a rough finishing of industrial substrates. Surface roughness and growth dynamics of TiC/a-C nanocomposite films deposited on such rough surfaces by non-reactive pulsed-DC (p-DC) sputtering of graphite targets at 350 kHz pulse frequency were studied using atomic force microscopy, cross-sectional scanning electron microscopy. Intensive concurrent ion impingement during the film growth at higher pulse frequency of p-DC sputtering leads to rapid smoothing of such initial rough surfaces. It was shown that rapid smoothing of initially rough surfaces with RMS roughness ~ 6 nm to < 1 nm can be effectively achieved by 350 kHz p-DC sputtering. These films exhibit dense and glassy microstructure. The surface roughness strongly influences the frictional behavior of TiC/a-C nanocomposite films where the rougher surfaces yielded higher steady state friction coefficient (CoF).The observed dynamic smoothing phenomenon was applied to obtain ultra-smooth and ultra-low friction (μ ~ 0.05) TiC/a-C:H nanocomposite films on industrial polished steel substrates by 200 and 350 kHz p-DC sputtering of Ti-targets in an argon/acetylene atmosphere.     

Deposition damage evaluation of fluorine doped silicon oxide using simple damage monitoring system

An arcing defect, generated during inter-metallic dielectric (IMD) fluorine doped silicon oxide (SiOF) film deposition, is fatal damage which occurs during the plasma enhanced deposition process. After IMD SiOF film deposition on the metal patterned wafer of logic device structure, the arcing defect is monitored using the KLA™ defect detecting tool. From KLA™ tool, it can be seen that the arcing defect has a close correlation with the deposition power so it is possible to reduce the arcing defect by decreasing the SiOF deposition power. The plasma charge from non-uniform plasma, induced during the SiOF film deposition, is characterized using the simple plasma damage monitoring (SPDM) system which is based on a very simple metal-oxide-silicon (MOS) capacitors. The SPDM system results show that the amount of the plasma charge from non-uniform plasma decreases as the SiOF deposition power decreases. This work focuses on finding an arcing defect free condition during IMD SiOF film plasma enhanced deposition on logic devices, by finding the “no plasma damage” condition. It is seen that when the SiOF film deposition at the high frequency (13.56 MHz) / low frequency (400 kHz) power condition is 500 W / 150 W or less, there is no plasma induced arcing defect. We report that the main cause of arcing defect, generated during SiOF film deposition, is the plasma charge from non-uniform plasma, induced during deposition process by using the SPDM system.     

Effect of microwave power and C2 emission intensity on structural and surface properties of nanocrystalline diamond films

Nanocrystalline diamond (NCD) films are synthesized using microwave plasma enhanced chemical vapour deposition technique at 2 × 10⁴ Pa and 600 °C with microwave power of 600-1600 W. Deposition is carried out on n-type (100) silicon wafer with Ar/H₂/CH₄ gas mixtures. The film properties are analyzed using micro Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy and atomic force microscopy. Raman spectra show two predominant peaks centered around 1335 cm⁻¹ and 1560 cm^− 1 and two humps around 1160 cm^− 1 and 1450 cm^− 1, respectively. FTIR spectra show C:H stretching modes around 3000 cm^− 1. XRD patterns show a peak at 44° (2θ). In situ diagnostic of plasma is carried out using Optical Emission Spectroscopy. It has been observed that C₂ dimer plays an important role in the nucleation of diamond crystals during NCD film deposition and the emission intensity of C₂ can be adjusted by varying the microwave power. It has also been observed that the structural properties like growth rate, surface morphology and grain size of the growing film are dependent on the C₂ intensity during deposition.     

等离子体化学气相沉积金刚石膜过程中光发射谱和朗谬尔探针原位诊断

报道了利用光发射谱(OES)和朗谬尔探针对热阴极直流放电等离子体化学气相沉积金刚石薄膜的等离子体条件进行原位研究的部分结果,研究了几种过程参数变化中等离子体状态,并与金刚石膜的沉积相联系。当CH     

Hydrogen-free diamond-like carbon films prepared by microwave electron cyclotron resonance plasma-enhanced direct current magnetron sputtering

Hydrogen-free diamond-like carbon (DLC) films were prepared by means of microwave electron cyclotron resonance plasma enhanced direct current magnetron sputtering. To study the influence of enhanced plasma on film fabrication and properties, the structures as well as mechanical and electrical properties of these films were studied as a function of applied microwave power. Results showed that higher microwave power could induce higher plasma density and electron temperature. The hardness increased from 3.5 GPa to 13 GPa with a variation of microwave power from 0 W to 1000 W. The resistivity showed a drastic increase from 4.5 × 10⁴ Ωcm at 0 W to 1.3 × 10¹⁰ Ωcm at 1000 W. The variation of the intensity ratio I(D)/I(G) and the position of the G-peak of the DLC films with respect to changes in microwave power were also investigated by Raman spectroscopy.     

Fabrication of carbon nanoneedle and carbon nanowall mixture film with two-step growth method

A novel nano-carbon electron emitter film has been developed on a stainless steel substrate by a direct current plasma chemical vapor deposition system. Samples grown at temperatures of 900 °C and 1100 °C showed different surface morphologies. It is found that a two-step growth process established by combining these two temperature growths together is suitable for deposition of a high density emitter array film. The as-grown nano-carbon film indicates a carbon nanoneedle and carbon nanowall mixture film, where the needle array density is about 3 × 10⁷/cm². The I-V characteristic shows an emission current density of 228 mA/cm² at 2.5 V/μm, and the field emission current is stable, making it possibly suitable for developing field emission devices.     

Effect of oxygen plasma treatment on bonding states for columnar structured a-CNx thin films prepared by reactive sputtering

Amorphous carbon nitride (a-CN) thin films were deposited on silicon single crystal substrates by rf-reactive sputtering method using a graphite target and nitrogen gas. The substrate temperature was varied from room temperature (RT) to 853 K. After deposition, the effect of oxygen plasma treatment on bonding structures of the film surface has been studied by using an oxygen discharge at 16 Pa and rf power of 85 W. The chemical bonding states and film composition were analyzed by X-ray photoelectron spectroscopy (XPS), while film thickness was obtained from scanning electron microscopy (SEM) and ellipsometer. XPS study revealed that the films have NO₂ and NO₃ bonding structures when the films are deposited at temperatures higher than 673 K. After exposure to oxygen plasma, carbon in the film surface was etched selectively and this phenomenon was observed in all films. In contrast, the surface concentration of nitrogen was ket at constant values before and after oxygen plasma treatment. The NO₃ bonding state had dramatically increased after oxygen plasma treatment for films deposited at higher deposition temperatures. The film surfaces have been observed to change the function from hydrophobic to hydrophilic after oxygen plasma treatment.     

Highly sensitive ultraviolet detector using a ZnO/Si layered SAW oscillator

This study elucidates a highly sensitive ultraviolet light detector using the combination of an oscillator circuit with a high-frequency amplifier, a matching network and a layered surface acoustic wave (SAW) device. In this structure, a ZnO thin film is simultaneously used as an active layer for UV detection and a piezoelectric layer for exciting a high-order surface acoustic wave. The microstructure and crystallization of ZnO films were investigated using the scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The SAW oscillator shows a good performance with output power of − 1.14 dBm and phase noise of −94.7 dBc at 100 kHz. Firstly, the frequency shifts of the oscillator exhibit rapid increase with the intensity of the UV light. Then the increased shifts decayed at certain UV intensity due to the saturated photogenerated carriers. An extreme frequency shift of 1017 kHz was obtained as the UV intensity reached 551 μW/cm². The maximum sensitivity of 8.12 ppm/(μW/cm²) can be obtained in this detector.     

High-rate synthesis of microcrystalline silicon films using high-density SiH4/H2 microwave plasma

A high electron density (> 10¹¹ cm^− 3) and low electron temperature (1-2 eV) plasma is produced by using a microwave plasma source utilizing a spoke antenna, and is applied for the high-rate synthesis of high quality microcrystalline silicon (μc-Si) films. A very fast deposition rate of ∼ 65 Å/s is achieved at a substrate temperature of 150 °C with a high Raman crystallinity and a low defect density of (1-2) × 10¹⁶ cm^− 3. Optical emission spectroscopy measurements reveal that emission intensity of SiH and intensity ratio of H_α/SiH are good monitors for film deposition rate and film crystallinity, respectively. A high flux of film deposition precursor and atomic hydrogen under a moderate substrate temperature condition is effective for the fast deposition of highly crystallized μc-Si films without creating additional defects as well as for the improvement of film homogeneity.     

Enhanced field emission from ZnO nanoneedles on chemical vapour deposited diamond films

ZnO nanoneedles were coated on hot filament chemical vapour deposited diamond thin films to enhance the field emission properties of ZnO nanoneedles. The virgin diamond films and ZnO nanoneedles on diamond films were characterized using scanning electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The field emission studies reveal that the ZnO nanoneedles coated on diamond film exhibit better emission characteristics, with minimum threshold field (required to draw a current density ~ 1 μA/cm²) as compared to ZnO needles on silicon and virgin diamond films. The better emission characteristic of ZnO nanoneedles on diamond film is attributed to the high field-enhancement factor resulting due to the combined effect of the ZnO nanoneedles and diamond film.     

The etching characteristics of Al2O3 thin films in an inductively coupled plasma

In this study, the etching characteristics of ALD deposited Al₂O₃ thin film in a BCl₃/N₂ plasma were investigated. The experiments were performed by comparing the etch rates and the selectivity of Al₂O₃ over SiO₂ as functions of the input plasma parameters, such as the gas mixing ratio, the DC-bias voltage, the RF power, and the process pressure. The maximum etch rate was obtained at 155.8 nm/min under a 15 mTorr process pressure, 700 W of RF power, and a BCl₃ (6 sccm)/N₂ (14 sccm) plasma. The highest etch selectivity was 1.9. We used X-ray photoelectron spectroscopy (XPS) to investigate the chemical reactions on the etched surface. Auger electron spectroscopy (AES) was used for the elemental analysis of the etched surfaces.     

Electron emission from Pb(Zr0.65Ti0.35)O3 film cathode by pulse electric field

Pulse electric field induced electron emission from the Pb(Zr_0.65Ti_0.35)O₃ ferroelectric films has been investigated as a function of the film thickness from 0.2 to 4.0 μm and the upper electrode diameter from 200 to 1100 μm. The electron emission charge from the 3.0 μm film was several nC per pulse, which was comparable to that of the bulk ferroelectrics. However, the local dielectric breakdown occurred in the films below 1.0 μm without the electron emission, which was confirmed by the optical microscopy observation after the emission tests. As the upper electrode size decreased and the film thickness increased, electrons were more easily emitted without breakdown.     

Electron-emission properties of carbon nanotube micro-tips coated by amorphous carbon nitride films

An approach to the preparation of a tip-type of field emitter that is made up of carbon nanotubes (CNTs) coated with amorphous carbon nitride (a-CN_x) films is presented for the purpose of enhancing its electron emission property. CNTs were directly grown on nano-sized conical-type tungsten tips via the inductively coupled plasma-chemical vapor deposition system, and a-CN_x films were coated on the CNTs using an radio frequency magnetron sputtering system. The morphologies and microstructures of the a-CN_x-coated CNTs were analyzed via field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy. The electron emission properties of the a-CN_x/CNT hetero-structures were measured using a high-vacuum field emission measurement system. The best field emission properties, such as a very low turn-on voltage of 500 V and a maximum emission current of 176 μA were achieved for the CNT emitter coated with the 5 nm-thick a-CN_x film. In addition, this emitter showed a highly stable behavior in long-term (up to 25 h) electron emission.     

SiO2 film deposition on the inner wall of a narrow polymer tube by a capacitively coupled μplasma

SiO₂ thin films were deposited on the inner wall of a narrow commercial poly(propylene) tube with inner/outer diameters of 1.0 mm/3.0 mm by plasma-enhanced chemical vapor deposition using He or Ar carrier gases and tetraethoxysilane (TEOS)/O₂ feedstock gases at high pressures from 30 kPa to atmospheric pressure and at room temperature. A glow μplasma was generated inside the tube by a radio frequency (RF 13.56 MHz) capacitively coupled discharge. X-ray photoelectron spectra and infrared spectra revealed that the inner surface of the plasma-treated tube was covered by a SiO₂ film. Scanning electron microscopy images indicated that the film produced by He/TEOS/O₂ μplasma had a smooth surface whereas the surface of the film produced by Ar/TEOS/O₂ μplasma appeared granulated. Typical deposition rates of approximately 300 nm/min were obtained by He/TEOS/O₂ μplasma at atmospheric pressure and a RF power of 11 W.     

Interaction of highly dissociated low pressure hydrogen plasma with W-C thin film deposits

Thin film deposits of carbon and tungsten on stainless steel substrate were prepared by RF sputtering of a tungsten target in acetylene atmosphere. At the target bias of − 1700 V and the target current of 30 mA cm^− 2, a rather uniform film containing 50 at.% of C and 50 at.% of W was deposited. The thickness of the deposited film was about 1 μm. Samples were exposed to highly dissociated hydrogen plasma created by a microwave discharge at the power of 1000 W. Some samples were heated additionally by concentrated solar radiation. After plasma treatment, the samples were characterized by X-Ray Diffraction and Auger Electron Spectroscopy. The results showed that aggressive hydrogen plasma allows for the removal of carbon from the deposits at moderated temperatures. Prolonged treatment showed formation of highly crystalline pure tungsten, and finally the tungsten film interacted with the substrate forming a thin film rich of Fe₇W₆ compound. The range of temperature and/or treatment time for the removal of carbon from the W-C film was found very narrow.     

Structural modification and enhanced electron emission from multiwalled carbon nanotubes grown on Ag/Fe catalysts coated Si-substrates

Multiwalled carbon nanotubes and carbon nano-filaments were grown using Fe as the main catalyst and Ag as a co-catalyst by microwave plasma enhanced chemical vapour deposition. In this work we demonstrate the growth behaviour of carbon nanotubes (CNTs) grown on pure Fe-film and Ag–Fe films. We find that using Ag film beneath Fe film significantly abate the catalyst–substrate interactions by acting as a barrier layer as well as enhances the nucleation sites for the growth of CNTs due to the limited solubility with Fe and silicon. Scanning electron microscopy and transmission electron microscopy studies were carried out to image the microstructures of the samples. It was observed that the length of Fe catalyzed CNTs was ∼500 nm and Ag–Fe catalyzed CNTs varied from ∼600 nm to 1.7 μm. Micro Raman spectroscopy confirmed the improved crystalline nature of Ag–Fe CNTs. It was found that I_D/I_G ratio for Fe catalyzed CNTs was ∼1.08 and for Ag–Fe catalyzed CNTs was ∼0.7. The Ag–Fe catalyzed CNTs were found to be less defective as compared to Fe catalyzed CNTs. Field emission measurements using diode configuration, showed that electron emission from Ag–Fe catalyzed CNTs was much stronger as compared to Fe catalyzed CNTs. The threshold field for Ag–Fe catalyzed CNTs was (2.6 V μm⁻¹) smaller as compared to Fe catalyzed CNTs (3.8 V μm⁻¹) and thus shows better emission properties. This enhancement in electron emission mechanism as a result of introduction of Ag underlayer is attributed to the increased emitter sites and improved crystallinity.