Inductively Coupled Plasma Chemical Vapor Deposition Research Articles

Organosilicon function of gas barrier films purely deposited by inductively coupled plasma chemical vapor deposition system

The novel design of inductively coupled plasma (ICP) source with the parallel electrodes embedded in quartz tubes was developed in this study. The advantages of the inductively coupled plasma chemical vapor deposition (ICPCVD) system were less ion-bombardment effect during the OLED encapsulation process and low cost to manufacture. The encapsulation structure of organosilicon/SiOx thin films deposited on flexible plastic substrates was purely deposited by the single chamber ICPCVD system under various hexamethyldisiloxane (HMDSO) and Ar flow ratios. To investigate the organosilicon film function, the ratio of HMDSO ambient was varied during deposition process and the associated bonding configurations were measured. With an adequate power of 400W and HMDSO atmosphere of 60%, the polymer-like organosilicon films were obtained due to the long chain structures. Finally, the water vapor transmission rate (WVTR) of one dyad barrier decreases to the 0.021g/m2/day due to the stress release of SiOx films caused by the polymer-like films.

Improvement in Si active material particle performance for lithium-ion batteries by surface modification of an inductivity coupled plasma-chemical vapor deposition

The high capacity and optimal cycle characteristics of silicon render it essential in lithium-ion batteries. The authors have attempted to realize a composite material by coating individual silicon (Si) particles of a few micrometers in diameter with a silicon oxide film to serve as an active material in the anode and so optimize the charge–discharge characteristics of the lithium-ion battery. Particle coating was achieved using an inductively coupled plasma-chemical vapor deposition (ICP-CVD) process that realized a homogenous coating of silicon oxide film on each Si particle. The film was synthesized based on tetraethyl orthosilicate (TEOS), with hydrogen (H2) gas used as a reducing agent to deoxidize the silicon dioxide. This enabled the control of the silicon oxidation number in the layers produced by adjusting the H2 flow during the silicon oxidization deposition with ICP-CVD. The silicon oxide covering the Si particles included both silicon monoxide and suboxide, which served to optimize the charge–discharge characteristics. The authors have succeeded in realizing a favorable active material using Si which is abundant in nature in the anode of a lithium-ion battery with highly charged, optimized cycle properties.

Controllable Synthesis of High-Quality Graphene Using Inductively-Coupled Plasma Chemical Vapor Deposition

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Controllable Synthesis of High-Quality Graphene Using Inductively-Coupled Plasma Chemical Vapor Deposition

High-quality graphene was synthesized on Cu foil using inductively-coupled plasma chemical vapor deposition (ICPCVD). ICP is very effective, such that a few-layer graphene could be formed within a few seconds. However, the graphene thickness was gradually decreased by increasing the growth time and plasma power, finally being saturated at a single layer. The graphene quality was also significantly enhanced by the preferential etching of the structurally-disordered C structures, followed by the newly synthesized graphene layer. Understanding ICPCVD growth kinetics, governed by the graphene formation by C atoms and C etching by H atoms, is useful for the controllable synthesis of high-quality graphene for various applications.

Fabrication of Transparent Protective Diamond-Like Carbon Films on Polymer

Si doped hydrogenated amorphous carbon (Si-DLC) films as a candidate protection coating for polycarbonate (PC) were prepared using a pulse-biased inductively coupled plasma chemical vapor deposition (ICP-CVD) system with a gas mixture of acetylene (C2H2) and tetramethylsilane [Si(CH3)4]. The effects of Si incorporation on the structure and optical properties of the Si-DLC films were investigated. In addition, plasma pretreatments with O2, N2, and Ar gases were carried out to enhance the adhesion strength of Si-DLC films on polycarbonate. Structural characterization through Raman and X-ray photoelectron spectroscopy (XPS) analyses showed that the incorporation of Si atoms in DLC films leads to an increase in the optical band gap (Eopt) with the formation of sp3 C–Si bonds. O2 plasma pretreatment improved the strength of adhesion of the Si-DLC films to polycarbonate, while Ar and N2 plasma treatments did not. This can be explained by the formation of an activated dense interfacial layer by O2 plasma pretreatment.

Fabrication of Transparent Protective Diamond-Like Carbon Films on Polymer

Si doped hydrogenated amorphous carbon (Si-DLC) films as a candidate protection coating for polycarbonate (PC) were prepared using a pulse-biased inductively coupled plasma chemical vapor deposition (ICP-CVD) system with a gas mixture of acetylene (C2H2) and tetramethylsilane [Si(CH3)4]. The effects of Si incorporation on the structure and optical properties of the Si-DLC films were investigated. In addition, plasma pretreatments with O2, N2, and Ar gases were carried out to enhance the adhesion strength of Si-DLC films on polycarbonate. Structural characterization through Raman and X-ray photoelectron spectroscopy (XPS) analyses showed that the incorporation of Si atoms in DLC films leads to an increase in the optical band gap (Eopt) with the formation of sp3 C–Si bonds. O2 plasma pretreatment improved the strength of adhesion of the Si-DLC films to polycarbonate, while Ar and N2 plasma treatments did not. This can be explained by the formation of an activated dense interfacial layer by O2 plasma pretreatment.

Permeation barrier coatings by inductively coupled plasma CVD on polycarbonate substrates for flexible electronic applications

Silicon oxide (SiO x)/silicon nitride (SiN x) stacks and parylene thin films were deposited on flexible polycarbonate (PC) substrates using inductively coupled plasma chemical vapor deposition (ICPCVD) and a parylene reactor for permeation barrier applications. The effects of gas flow ratios on SiN x and SiO x film properties in terms of refractive index, internal stress, and water vapor transmission rate (WVTR) were investigated. It was found that the optical property and impermeability of SiN x and SiO x barrier films could be tailored by varying the gas flow ratio. The details of Ar plasma treatment effects on PC substrates in terms of contact angle, roughness, and WVTR were studied. The WVTR value of the optimum barrier structure (parylene + 3 pairs of SiO x/SiN x) could reduce to 4.74 × 10 −5 g/m 2/day after bending for 1000 times under a resistivity test (25 °C and 90% relative humidity). This result indicated that permeation barrier films prepared by ICPCVD could be a promising candidate for flexible electronic applications.

Deposition and characterization of low temperature silicon nitride films deposited by inductively coupled plasma CVD

Silicon nitride films have been deposited at a low temperature (70 °C) by inductively coupled plasma chemical vapor deposition (ICP-CVD) technique and their physical and chemical properties were studied. For a deposited SiN sample, β-phase was observed and refractive index of 2.1 at 13.18 nm/min deposition rate was obtained. The attained stress of 0.08 GPa is lower as compared to the reported value of 1.1 GPa for SiN thin films. To study the deposited film, characterization was performed using X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), micro Raman spectroscopy, Fourier transfer infrared spectroscopy (FTIR), cross-section scanning electron microscopy (SEM) and atomic force microscopy (AFM).

Optimisation and fabrication of low-stress, low-temperature silicon oxide cantilevers

Modern lab-on-a-chip systems can benefit from integration of nanoelectromechanical system/microelectromechanical system (NEMS/MEMS) and complementary metal–oxide semiconductor technology with emphasis on low temperature processing. In the present work process, parameters for deposition of silicon oxide (SiOx) by inductively coupled plasma chemical vapour deposition (ICPCVD) at low temperature (70°C) are optimised. The sacrificial layer poly(methyl methacrylate) (PMMA) is in-house prepared and optimised. This PMMA sacrificial solution not only gives a low cost wide range of viscosity solutions, but it is also low temperature NEMS process compatible. With optimisations mentioned above, it has been possible to fabricate the whole device without exceeding the thermal budget 100°C. To the best of the authors' knowledge, this is the first report on sub-100°C, surface micromachined SiOx cantilevers deposited by ICPCVD and using PMMA as the sacrificial layer for low temperature NEMS applications.

Field Emission from Individual Free-Standing Carbon Nanotubes

The field emission (FE) characteristics of individual free-standing vertically aligned carbon nanotubes (VACNTs) grown by inductively coupled plasma chemical vapor deposition (ICP-CVD) were studied. The processes comprised electron beam lithography (EBL) with various exposure periods, the deposition of nickel metal followed by lift-off, and the growth of carbon nanotubes by ICP-CVD on a <100> p-type silicon substrate. Straight tubular and stubby conical VACNFs were formed by varying the size of the graphite electrode that supports the silicon substrate. Current–voltage (I–V) curve characteristics for the tubular shape of isolated carbon nanotubes with different diameters and lengths were studied. The lowest turn-on voltage was shown to be about 24.5 V for the highest aspect ratio of a single vertically-aligned CNT. The highest field enhancement factor β determined from fitting the FN equation was about 110. In addition, the enhancement factor was proportional to the aspect ratio of the CNTs. The turn-on field at an emission current of 1 nA was 8–12 V/µm for a single straight tubular VACNT and 4–8 V/µm for a stubby conical VACNF. The stubby conical CNFs (with smaller radii of curvature of their tips) had a lower turn-on field, but a slightly lower β, than the long tubular CNTs (with higher aspect ratio).

X-ray images obtained from cold cathodes using carbon nanotubes coated with gallium-doped zinc oxide thin films

X-ray imaging data obtained from cold cathodes using gallium-doped zinc oxide (GZO)-coated CNT emitters are presented. Multi-walled CNTs were directly grown on conical-type (250 μm-diameter) tungsten-tip substrates at 700 °C via inductively coupled plasma-chemical vapor deposition (ICP-CVD). GZO films were deposited on the grown CNTs at room temperature using a pulsed laser deposition (PLD) technique. Field-emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) were used to monitor the variations in the morphology and microstructure of the CNTs before and after GZO coating. The formation of the GZO layers on the CNTs was confirmed using energy-dispersive X-ray spectroscopy (EDX). The CNT-emitter that was coated with a 10-nm-thick GZO film displayed an excellent performance, such as a maximum emission current of 258 μA (at an applied field of 4 V/μm) and a threshold field of 2.20 V/μm (at an emission current of 1.0 μA). The electric-field emission characteristics of the GZO-coated CNT emitter and of the pristine (i.e., non-coated) CNT emitter were compared, and the images from an X-ray system were obtained by using the GZO-coated CNT emitter as the cold cathode for X-ray generation.

Coating of carbon nanotubes with amorphous carbon nitride thin films and characterization of long-term emission stability

The effects of amorphous carbon nitride (CN) thin films that were coated on carbon nanotubes (CNTs) and their thermal treatment were investigated, in terms of the chemical bonding and morphologies of the CNTs and their field emission properties. CNTs were directly grown on conical tip-type tungsten substrates via the inductively coupled plasma-chemical vapor deposition (ICP-CVD) system, and the CNTs were coated with CN films using the RF magnetron sputtering system. The CN-coated CNTs were thermally treated using the rapid thermal annealing (RTA) system by varying the temperature (300–700 °C). The morphologies, microstructures, and chemical compositions of the CN-coated CNTs were analyzed as a function of the thickness of the CN layers and the RTA temperatures. The field emission properties of the CN/CNT hetero-structured emitters, and the fluctuation and long-term stability of the emission currents were measured and compared with those of the conventional non-coated CNT-emitter. The results showed that the electron emission capability of CNT was noticeably improved by coating a thin CN layer on the surface of the CNT. This was attributed to the low work function and negative electron affinity nature of the CN film. The CN-coated CNT-emitter had a more stable emission characteristic than that of the non-coated one. In addition, the long-term emission stability of the CN-coated emitter was further enhanced by thermal treatment, which was verified by x-ray photoelectron spectroscopy (XPS) analysis.

The optoelectronic properties of silicon films deposited by inductively coupled plasma CVD

Hydrogenated amorphous and microcrystalline silicon films were deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD) at low substrate temperatures using H 2-diluted SiH 4 as a source gas. High-density plasma generated by inductively coupled excitation facilitates the crystallization of silicon films at low temperatures, and microcrystalline silicon films were obtained at the substrate temperature as low as 180 °C. The columnar structure of the films becomes more and more compact with an increase of their crystallinity. The reduction of hydrogen content in the films causes a narrowing of the optical bandgap and an enhancement of the absorption with increasing the substrate temperature. The microcrystalline silicon films show two electronic transport mechanisms: one is related to the density of state distribution in the temperature region near room temperature and the other is the variable range hopping between localized electronic states close to the Fermi level below 170 K. A reasonable explanation is presented for the dependence of the optoelectronic properties on the microstructure of the silicon films. The films prepared at a substrate temperature of 300 °C have highly crystalline and compact columnar structure, high optical absorption coefficient and electrical conductivity, and a low hydrogen content of 3.8%.

Synthesis of functional diamond-like carbon nanocomposite films containing titanium dioxide nanoparticles

Synthesis of diamond-like carbon (DLC) films with UV-induced-hydrophilicity function was studied by inductively-coupled plasma (ICP) chemical vapor deposition. Titanium tetraisopropoxide (TTIP) and oxygen gases were employed as the precursors to deposit diamond-like nanocomposite films containing titanium dioxide (TiO 2) nanoparticles. X-ray diffraction and high-resolution transmission electron microscopy revealed that TiO 2 nanocrystallites were formed in the DLC films when oxygen concentration was higher than TTIP concentration during deposition. The DLC nanocomposite film was hydrophobic without ultraviolet (UV) irradiation, and became highly hydrophilic under UV irradiation, exhibiting the self-cleaning effect. A very broad peak centered at 1580 cm − 1 was observed in the Raman spectra confirming the formation of DLC films. The hardness of the film was about 8 GPa with a stress of 3 GPa. ICP was essential in forming the photocatalytic TiO 2 nanoparticles in the DLC matrix.

Preparation of Born-Doped a-SiC:H Thin Films by ICP-CVD Method and to the Application of Large-Area Heterojunction Solar Cells

Hydrogenated amorphous silicon carbide (a-SiC:H) film has been widely used as an emitter p layer in solar cells. For the better p layer, wide optical bandgap, and high electrical conductivity should be obtained from the effective method. We prepared the boron-doped a-SiC:H thin films using inductively coupled plasma chemical vapor deposition (ICP-CVD) method and characteristics on the small-area (2 cm x 2 cm) as well as the large-area films (diameter of 100 mm) were shown on it. As a substrate, the n-type (100) oriented CZ c-Si (5.5 approximately 6.5 omega x cm, 650 microm) wafers were used and cleaned by using the reduced RCA method. A silane (SiH4) of 99.999% purity, H2 and 60% hydrogen diluted ethylene (C2H4) was used as source gas for the deposition of intrinsic a-SiC:H films, and then diborane (B2H6), as the doping gas, is added to C2H4 and SiH4/H2 during the deposition of films. The uniformity of thickness and optical bandgap from large-area as-dep. films was at 1.8% and 0.3%, respectively. Heterojunction solar cell with 2 wt%-AZO/p-a-SiC:H/i-a-Si:H/c-Si/Ag structure was fabricated and characterized with diameter of 152.3 mm in this large-area ICP-CVD system. Conversion efficiency of 9.123% was achieved with a practical area of 100 mm x 100 mm, which can show the potentials to the fabrication of the large-area solar cell using ICP-CVD method.

Effect of Pulsed Substrate Bias on Film Properties of SiO2 Deposited by Inductively Coupled Plasma Chemical Vapor Deposition

A high-quality SiO2 film was successfully achieved at a temperature of 150 °C by inductively coupled plasma chemical vapor deposition (ICP-CVD) with a bipolar pulsed bias applied to a substrate. When the SiO2 film was deposited without the pulsed substrate bias, its density rapidly decreased and its insulating property deteriorated. However, its densification was enhanced and its insulating property was improved by the pulsed substrate bias even though the deposition rate increased. A leakage current of less than 10.0 nA/cm2 and a breakdown voltage of 5.2 MV/cm at 1.0 µA/cm2 were obtained at a temperature of 150 °C with a deposition rate of 18.0 nm/min.

The metal-induced crystallization of poly-Si and the mobility enhancement of thin film transistors fabricated on a glass substrate

In this study, we report on the fabrication of poly-crystalline silicon (poly-Si) using the metal-induced crystallization (MIC) method and its application to thin film transistors (TFTs). The top gate of the p-type TFTs, whose active layer used MIC poly-Si annealed for 1 h at 650 °C, showed a field effect mobility ( μ FE) of 7.5 cm 2/V s. By increasing the crystallization time to 5 h, the quality of the MIC poly-Si was improved. The μ FE increased from 7.5 to 15 cm 2/V s. In order to enhance the channel mobility, the Si dangling bonds, which were produced during the transformation from the amorphous phase to the poly-crystalline phase of silicon (Si), were reduced by using plasma hydrogenation. Measurements show that the μ FE reached 45 cm 2/V s after passivation by an inductively coupled plasma chemical vapor deposition (ICPCVD) system.

Electron Emission Properties of Hetero-Junction Structured Carbon Nanotube Microtips Coated With BN And CN Thin Films

Boron nitride (BN) and carbon nitride (CN) films, which have relatively low work functions and commonly exhibit negative electron affinity behaviors, were coated on carbon nanotubes (CNTs) by magnetron sputtering. The CNTs were directly grown on metal-tip (tungsten, approximately 500nm in diameter at the summit part) substrates by inductively coupled plasma-chemical vapor deposition (ICP-CVD). The variations in the morphology and microstructure of CNTs due to coating of the BN and CN films were analyzed by field-emission scanning electron microscopy (FE-SEM). The energy dispersive x-ray (EDX) spectroscopy and Raman spectroscopy were used to identify the existence of the coated layers (CN and BN) on CNTs. The electron-emission properties of the BN-coated and CN-coated CNT-emitters were characterized using a high-vacuum field emission measurement system, in terms of their maximum emission currents (Imax) at 1kV and turn-on voltage (Von) for approaching 1µA. The results showed that the Imax current was significantly increased and the Von voltage were remarkably reduced by the coating of CN or BN films. The measured values of Imax-Von were as follows; 176µA-500V for the 5nm CN-coated emitter and 289µA-540V for the 2nm BN-coated emitter, respectively, while the Imax-Von of the as-grown (i.e., uncoated) emitter was 134µA-620V. In addition, the CNT emitters coated with thin CN or BN films also showed much better long-term (up to 25h) stability behaviors in electron emission, as compared with the conventional CNT emitter.

The effects of rapid thermal annealing on the performance of ZnO thin-film transistors

We fabricated and characterized zinc oxide (ZnO)-based thin-film transistors (TFTs) on a glass substrate, which can also be applied to plastic substrates such as polyimide or polynorbornene, at a maximum process temperature of 300 ◦C. Most of the component layers in ZnO-TFTs with a bottom-gate configuration were deposited by using rf magnetron sputtering techniques, except for the SiO2 gate insulating layer, which was deposited by using inductively coupled plasma chemical vapor deposition (ICP-CVD). Silicon-dioxide (SiO2) and ZnO layers were separately heat-treated at 300 ◦C by rapid thermal annealing (RTA) to study its effect on the device performance. The RTAtreated film had a surface morphology similar to that of the as-deposited film, but demonstrated higher crystallinity and transmittance, in addition to enhanced electrical properties, such as carrier concentration and mobility. When the SiO2 layer was RTA-treated before the ZnO deposition, the ZnO TFTs showed high field effect mobility and high on/off current ratio. As a result of the lowtemperature RTA treatment, we successfully fabricated high-performance and highly-transparent ZnO-TFTs. This process should be promising for various displays, such as organic light emitting diode (OLED) and liquid crystal display (LCD) that require low-temperature processes.

Effect of N 2O/SiH 4 flow ratios on properties of amorphous silicon oxide thin films deposited by inductively-coupled plasma chemical vapor deposition with application to silicon surface passivation

Silicon oxide (SiO x) thin films have been deposited at a substrate temperature of 300 °C by inductively-coupled plasma chemical vapor deposition (ICP-CVD) using N 2O/SiH 4 plasma. The effect of N 2O/SiH 4 flow ratios on SiO x film properties and silicon surface passivation were investigated. Initially, the deposition rate increased up to the N 2O/SiH 4 flow ratio of 2/1, and then decreased with the further increase in N 2O/SiH 4 flow ratio. Silicon oxide films with refractive indices of 1.47–2.64 and high optical band-gap values (>3.3 eV) were obtained by varying the nitrous oxide to silane gas ratios. The measured density of the interface states for films was found to have minimum value of 4.3 × 10 11 eV −1 cm −2. The simultaneous highest τ eff and lowest density of interface states indicated that the formation of hydrogen bonds at the SiO x/c-Si interface played an important role in surface passivation of p-type silicon.