The dependence of hardness on the density of amorphous alumina thin films by PECVD

Smooth, uniform and transparent aluminum oxide films were deposited at low temperature (≤ 500°C) by r.f. plasma enhanced chemical vapor deposition (PECVD) with AlCl₃, H₂ and CO₂ as the reactants. The measurements of mechanical and optical properties demonstrate a potential application of PECVD aluminum oxide film as an optical protective coating. The variation of film hardness and density with deposition parameters is apparent and shows a similar dependence while the composition stoichiometry is not so influenced. For amorphous thin films incorporating hydrogen and/or microvoid with no apparent variation on composition stoichiometry, the film hardness is dominated by density and a function near linear can be constructed as energy density is taken into account as an apparent character of hardness.     

SiO2/TiO2 thin films with variable refractive index prepared by ion beam induced and plasma enhanced chemical vapor deposition

SiO₂/TiO₂ optical thin films with variable compositions have been prepared by ion beam induced and plasma enhanced chemical vapour deposition (IBICVD and PECVD). While the films obtained by IBICVD were very compact, the PECVD ones with a high content of Ti presented a columnar microstructure. The formation of Si–O–Ti bonds and a change in the environment around titanium from four- to six-coordinated has been proved by vibrational and X-ray absorption spectroscopies. The refractive index increased with the titanium content from 1.45 to 2.46 or 2.09 for, respectively, the IBICVD and PECVD films. Meanwhile, the band gap decreased, first sharply and then more smoothly up to the value of pure TiO₂. It is concluded that the optical properties of SiO₂/TiO₂ thin films can be properly tailored by using these two procedures.     

Plasma-enhanced chemically vapour deposited Si3N4 thin films for optical waveguides

Silicon nitride films for applications in optical waveguides have been deposited by plasma-enhanced chemical vapour deposition (PECVD). Index of refraction, deposition rate, buffered HF etch rate and hydrogen content have been measured for different NH₃-to-SiH₄ ratios of precursor gases in the range 0.6–10. Results show that these magnitudes are nearly constant for 2NH₃:SiH₄4. Thermal annealing of films deposited at high NH₃:SiH₄ ratios yields a large reduction (up to 70%) in the N---H bond concentration as well as a densification of the films. Finally, geometrical parameters necessary for the design of rib-type monomode optical waveguides based on the PECVD silicon nitride films were calculated.     

IR spectra and etch rates of plasma-enhanced chemically vapour-deposited phosphosilicate glass films

IR transmission spectra of phosphosilicate glass (PSG) films with 8 wt.% P prepared by plasma-enhanced chemical vapour deposition (PECVD) and CVD are compared. The differential IR spectrum of a PECVD PSG film differs from that of a CVD PSG film: the P=O peak has a lower intensity than the corresponding peak of the CVD film with the same phosphorus content; no peaks are evident at 980 and 500 cm⁻¹—the characteristic frequencies for P---O---P stretching and bending vibrations. The differential IR spectra of PECVD and CVD PSG films become very similar after annealing for 4 h in water vapour at 850°C. The etch rate of a PECVD film in p-etchant, which is constant throughout the film thickness, is 400 Å min⁻¹. However, the etch rate recorded after the film is subjected to annealing in water vapour at 850°C varies with the depth in the film, attaining values as high as 800 Å min⁻¹ in the region near the outer surface of the film. The results are explained as due to the oxidation of P₂O₃ to P₂O₅.     

PECVD制程中N+A-SI Layer沉积最佳工艺参数的探究

本文采取4因子4水平田口设计,用等离子体增强化学气相沉积法制备了沉积在白玻璃上的单层N+A-SI:H薄膜,测试了薄膜的应力,膜厚,折射率,透过率,及SI-H/N-H键含量,综合评价不同参数配比条件下N+A-SI:H单层膜的膜质表现,针对比较重要的参数:沉积速率,Thickness Uniformity,SI-H键含量进行了田口分析,两阶段策略优化选出PECVD制程中的N+A-SI layer的最佳参数配比为:Pressure-385.7 Pa,Spacing-20.32 mm,RF Power-13000W,Gas Ratio-3.12。     

Intermediate gas phase precursors during plasma CVD of HMDSO

In plasma enhanced chemical vapor deposition (PECVD) from complex molecules like hexamethyldisiloxan (HMDSO) often not the molecules themselves but intermediate and reactive radicals or molecules are the precursors for film growth. Additionally, such PECVD processes are volume or mass flow limited under many process conditions. In these cases growth rate and film homogeneity is mainly dominated by the precursor content and its spatial distribution in the gas or plasma phase. Therefore the identification of such intermediate precursors is an important task to optimize a PECVD process and also helps us to understand the plasma chemical reactions during PECVD. A combined mass spectrometry and IR absorption study is used to identify intermediate gas phase precursors in HMDSO/O₂ PECVD remote plasmas. For this study a microwave plasma CVD system was used with HMDSO/O₂ ratios between 0.1 and 1 at typical operating pressures between 20 and 70 Pa. Three reactive intermediate species are proposed to act as a precursor for SiO_x film growth from HMDSO/O₂ plasmas. All three having a mass of 148 amu. The related reactive groups are the silanon (Si=O), silanol (Si-OH) and aldehyde (C=O) groups.     

Effects of spray parameters on the microstructure and property of Al2O3 coatings sprayed by a low power plasma torch with a novel hollow cathode

Al₂O₃ coating is deposited using a low power plasma torch with a novel hollow cathode through axial powder injection under a plasma power up to several kilowatts. The effects of the main processing parameters including plasma arc power, operating gas flow and spray distance on particle velocity during spraying, and the microstructure and property of the coating are investigated. The microstructure of the Al₂O₃ coating is examined using optical microscopy and X-ray diffraction analysis. The property of the coating is characterized by dry rubber wheel abrasive wear test. The velocity of in-flight particle is measured using a velocity/temperature measurement system for spray particle based on thermal radiation from the particle. The dependency of the microstructure and property of the coating on spray particle conditions are examined by comparing the particle velocity, and microstructure and abrasive wear weight loss of subsequent coating deposited by low power plasma spray with those of the coating by conventional plasma spray at a power one order higher. X-ray diffraction analysis of the coating revealed that Al₂O₃ particles during low power plasma spraying reach to sufficiently melting state prior to impact on the substrate with a velocity comparable to that in conventional plasma spraying. The experiment results have shown that processing parameters have significant influence on the particle conditions and performance of deposited Al₂O₃ coating. The coating of comparable microstructure and properties to that deposited by conventional plasma spray can be produced under a power one order lower. From the present study, it can be suggested that a comparable coating can be produced despite plasma power level if the comparable particle velocity and molten state are achieved.     

磁激活等离子体增强化学气相沉积设备的研制

针对PECVD中等离子体的密度沿径向分布均匀性较差、空间气氛化学活性较差的问题,在PECVD的基础上加入电子发射源和正交电磁场以控制电子的运动,从而增强等离子场的强度和范围,使反应场的活力增加,以提高反应空间的活化能力,继而提高膜层质量.结果表明,该方法可以使等离子场的分布发生改变,使等离子体密度及范围做到可控制且可调整.     

Highly homogeneous silica coatings for optical and protective applications deposited by PECVD at room temperature in a planar uniform distributed electron cyclotron resonance plasma reactor.

Thin near-stoichiometric silica films were deposited by plasma-enhanced chemical vapour deposition (PECVD) using pure SiH₄ and O₂ in a planar plasma reactor based on the proprietary uniform distributed electron cyclotron resonance (UDECR) technology. Samples were kept approximately at room temperature during the process. In the pressure range 0.1–0.4 Pa, dense ( > 5 × 10¹⁰ cm⁻³) diffusion plasmas could be sustained very homogeneously over areas larger than 200 mm× 200 mm. In conjunction with appropriate distributed gas injection set-up, extremely good layer uniformities were obtained, with no visible irisations for thicknesses of 0.1–6 μm. The reactor concept intrinsically lends itself to process scale-up which is even trivial along one dimension. The effects of gas flow rates and substrate r.f. bias were investigated, mainly by Fourier transform infrared absorption spectroscopy and spectroscopic ellipsometry (1.4–5.0 eV). The Si-H and O-H bond contents were found to be very low for all samples. For films deposited under sufficient ion bombardment energy, typical values for the refractive index at 2.0 eV (1.458) and the Si-O-Si stretching frequency (1075 cm⁻¹) were very close to those obtained in the case of thermally grown silica, indicating an unusually dense microstructure for the as-deposited PECVD films grown at quasi-ambient temperature.

Transparent protective coatings 3–5 μm thick showing excellent abrasion resistance and weatherability could thus be deposited on metals and optical polymers.     

Pulsed-radio frequency plasma enhanced chemical vapour deposition of low temperature silicon nitride for thin film transistors

The growth of low temperature silicon nitride using radio frequency (RF) plasma enhanced chemical vapour deposition (PECVD) is associated with high porosity and surface roughness due to the short surface diffusion length of adsorbed radicals during the deposition. In this work we present pulsed-RF PECVD as a means of achieving a film with smoother surface and reduced density of voids. The growth process and the longer surface diffusion length are discussed as the main reason behind improvement of film density while maintaining the substrate temperatures. The deposited films exhibit improved electrical performance with 72% reduction in breakdown probability compared with conventional continuous-wave RF PECVD films. A low interfacial defect density with a field effect mobility of 1.1 cm²/V.s and subthreshold slope of 0.3 V/dec, was achieved when used as a gate dielectric in thin film transistors.     

Transparente Barriereschichten auf flexiblen Polymersubstraten

Transparent permeation barrier layers on flexible polymer substrates This paper reviews different vacuum based technologies for manufacturing transparent permeation barrier layers and layer stacks on flexible polymer substrates. With plasma assisted reactive evaporation, a cost‐efficient, highly productive process for food packaging applications is presented. Reactive dual magnetron sputtering is a technology for the deposition of oxide layers with a very low water vapor and oxygen transmission rate at a reasonable deposition rate. Many groups suggest multilayer stacks for the encapsulation of flexible electronic devices. In this paper, an all‐in‐vacuum inline concept for manufacturing such multilayers is presented. It is based on the combination of reactively sputtered barrier layers with interlayers grown by using a magnetron based PECVD process (Magnetron‐PECVD). Both, process parameters, such as deposition rate and process pressure, and important layer properties, such as morphology and the water vapor and oxygen transmission rate are compared for the different single and multi layer technologies.     

Leakage Current Analysis of Nitride-Based Photodetectors by Emission Microscopy Inspection

Leakage properties of nitride-based photodetectors (PDs) subjected to inductively coupled plasma (ICP) etching has been investigated by using emission microscopy inspection (EMMI). ICP etching would cause significant damage to GaN metal-semiconductor-metal (MSM) PDs. The damage was proven to induce leakage current via the conductive surface of the device by using emission microscopy inspection. However, the surface damage of MSM PDs could be partially recovered by E-beam SiO₂ passivation. As for the passivation for p-i-n photodetectors, the effect was not significant in the reduction of dark current due to smaller etched area as compared to the whole area of p-i-n PDs. The leakage current path analysis of p-i-n PDs by EMMI technique had also been investigated. Finally, the plasma enhanced chemical vapor deposition (PECVD) SiO₂ passivation was proven to be a potential process to improve the reliability of p-i-n PDs.     

Low temperature synthesis of single-walled carbon nanotubes in an inductively coupled plasma chemical vapor deposition system

In this work, we present a parametric study on the low temperature synthesis of single-walled carbon nanotubes (SWNTs) in an inductively coupled plasma (ICP) CVD system using dry bi-layered catalytic thin-films (Fe/Al and Ni/Al, deposited by electron-beam evaporation method) as the catalysts. With a low substrate temperature of 550 degrees C and above, SWNTs were successfully synthesized on both catalysts, as revealed from the characteristic peaks of SWNTs in the micro-Raman spectra. By the reduction of plasma power and the shortening of the process times, the lowest synthesis temperature of SWNTs achieved in our system was approached to 500 degrees C on Ni/Al catalysts; on the other hands, the lowest temperature for Fe/Al catalysts was 550 degrees C. Our results suggest that as compared with Fe/Al, Ni/Al is more favorable for plasma-enhanced CVD (PECVD) synthesis of SWNTs at low temperatures. This work can be used for further improvements and better understanding on the production processes of SWNTs by PECVD methods.     

Crystallization by excimer laser annealing for a-Si:H films with low hydrogen content prepared by Cat-CVD

Crystallization by excimer-laser annealing (ELA) for hydrogenated amorphous silicon (a-Si:H) films with low hydrogen content (C_H) prepared by catalytic chemical vapor deposition (Cat-CVD) was systematically studied. From optical microscopy images, no hydrogen bubbling was observed during ELA, even without a dehydrogenation process. As the laser energy density was increased to 300 mJ cm⁻², the full width at half-maximum of the Raman signal from the crystalline phase decreased to approximately 4 cm⁻¹. This value is almost equal to or even smaller than that reported for polycrystalline Si (poly-Si) films prepared from plasma-enhanced CVD (PECVD) a-Si:H films by ELA so far. The average grain size, estimated from scanning electron microscopy, was approximately 500 nm for C_H of 1.3 at.%. On the other hand, the grain size of poly-Si films prepared from PECVD a-Si:H films with a dehydrogenation process was only 200 nm. The technique using Cat-CVD films is expected to be used for fabrication of low-temperature high-mobility thin-film transistors.     

Cubic Boron Nitride Formation by PECVD in the B-N-Cl-H System: Ionic and Chemical Aspects

BN thin films have been synthesized by r.f. Plasma Enhanced Chemical Vapor Deposition (PECVD) from BCl₃ / N₂ /H₂ / Ar mixtures. c-BN formation has been studied through correlations between gas phase characterization (by Optical Emission Spectroscopy, Mass Spectrometry and electrical measurements) and thin film analysis (by Fourier Transformed Infra Red Spectrometry for structure determination).

In particular, the occurrence of physical and possible chemical mechanisms is studied with the help of post-treatments of as-deposited BN coatings in pure Ar, Ar/H₂ and Ar/Cl_b plasma mixtures. It is shown that, in addition to the well known ion-induced formation of the cubic phase, chemical etching also occurs, due to the presence of hydrogen and chlorine species, which leads to a relative increase in the cubic content of the thin film.     

High deposition rate processes for the fabrication of microcrystalline silicon thin films

The increase of deposition rate of microcrystalline silicon absorber layers is an essential point for cost reduction in the mass production of thin-film silicon solar cells. In this work we explored a broad range of plasma enhanced chemical vapor deposition (PECVD) parameters in order to increase the deposition rate of intrinsic microcrystalline silicon layers keeping the industrial relevant material quality standards. We combined plasma excitation frequencies in the VHF band with the high pressure high power depletion regime using new deposition facilities and achieved deposition rates as high as 2.8 nm/s. The material quality evaluated from photosensitivity and electron spin resonance measurements is similar to standard microcrystalline silicon deposited at low growth rates. The influence of the deposition power and the deposition pressure on the electrical and structural film properties was investigated.     

Plasmachemische Gasphasenabscheidung – eine Technologie zur Deposition organischer und anorganischer Schichten. Plasma Enhanced Chemical Vapor Deposition – a Thin Film Technique for Organic and Inorganic Layers

Plasma enhanced chemical vapor deposition (PECVD) has a wide range of interest for thin films up to some μm thickness. It has widespread applications for high quality dielectric and semiconducting silicon alloys at deposition temperatures below 450 °C and pressures at 1 mbar on plane substrates and attracts growing attention for the surface modification of polymers. The PECVD takes advantages of the possibility to alter the film properties in a wide range easily, and the coatings can achieve a variety of useful properties unobtainable by other coating techniques. An environmentally friendly plasma chemical reactor etch cleaning of SiO_x, SiN_x and other film materials can be applied by changing the process gas and without breaking the vacuum. PECVD can be used in a fixed substrate and continuous substrate flow mode. An capacitively coupled parallel‐plate electrode assembly using radio‐frequency (RF) excitation of the discharge is most widely used for substrate areas up to a few square meters. Among the capacitively excitation an inductively and electromagnetically excitation at frequencies in the RF and UHF range has also succeeded in achieving a high rate PECVD. Two applications are presented to show the characteristics and the potential of this technique, the PECVD of semiconducting hydrogenated amorphous silicon, intrinsic or doped, with low power densities using monosilane as a source gas for solar cells, thin films transistors and digital image sensors and the plasma polymerisation of organosilicon protection layers employing the HMDSO monomer and high power densities for mirrors and lenses.     

Die Hochleistungsmikrowellenquelle Miro

The high‐performance microwave source Miro – Plasma characterization and applications in PECVD and combination sputtering processes To evaluate the potential of the high‐efficiency microwave source Miro 200 CI the properties of plasma processes were investigated focusing at PECVD coatings of a‐C:H‐ and SiO_x as relevant applications. The sources were also intensively characterized by plasma diagnostic methods, e.g. by optical emission spectroscopy and electrical plasma probes. The analysis of the real efficiency of individual sources with slight changes in construction could be used to come to an optimized design. The Miro sources are able to create an extensive working volume showing relative homogeneous deposition rates of currently 35μm/h for a‐C:H and 25 μm/h for SiO_x. An arrangement of multiple sources enables PECVD processes for large area coating at a pressure level close to those commonly used with PVD sources. So, post‐oxidation of sputtered layers with the Miro source could be used beneficially to obtain optical oxide layers with lower absorption. Combinations with HIPIMS sputter sources lead to efficient deposition processes of coatings for tribological applications.     

低温沉积SiO2薄膜工艺的研究

利用等离子体增强化学气相沉积系统（PECVD）研究SiO2薄膜低温制备工艺,分析工艺条件对薄膜性能参数影响,通过调节射频功率优化薄膜应力,在150℃低温下获得接近零应力SiO2薄膜,薄膜沉积速率约为40nm／min,片内均匀性优于3％,折射率为1．46±0．003,并具有良好的附着力和抗蚀性能。由于沉积温度低,薄膜性能好,因此可以作为绝缘层或介质层,应用于柔性电子领域。     

Improvement of thermal contact resistance by carbon nanotubes and nanofibers

Interfacial thermal resistance results of various nanotube and nanofiber coatings, prepared by chemical vapor deposition (CVD) methods, are reported at relatively low clamping pressures. The five types of samples examined include multi-walled and single-walled nanotubes growth by CVD, multi-walled nanotubes grown by plasma enhanced CVD (PECVD) and carbon nanofibers of differing aspect ratio grown by PECVD. Of the samples examined, only high aspect ratio nanofibers and thermally grown multi-walled nanotubes show an improvement in thermal contact resistance. The improvement is approximately a 60% lower thermal resistance than a bare Si-Cu interface and is comparable to that attained by commercially available thermal interface materials.