Inductively Coupled Plasma Enhanced Chemical Vapor Deposition Research Articles

Growth Mechanism of High-Quality hBN Monolayers on Cu through Chemical Vapor Deposition with Inductively Coupled Plasma

The growth mechanism associated with the nucleation and growth kinetics of hexagonal boron nitride (hBN) on Cu through chemical vapor deposition (CVD) has been studied. A fully covered hBN film with a large grain size has been obtained by lowering the density of the grain boundary during the thermal CVD. The Cu substrate is first annealed under the H2 ambiance in order to efficiently reduce the copper oxide on the surface and promote the Cu surface with the (111) plane. Next, the nucleation and growth kinetics of CVD hBN are investigated by the analysis of scanning electron microscopy (SEM) images and the Johnson–Mehl–Avrami–Kolmogorov model. The hBN growth is overall dominated by nucleation under a low flow rate of H2, while it is initially dominated by grain growth under a high flow rate of H2 and the grain size of hBN can be larger than 25 μm. The competition between nucleation and grain growth is reversed at higher temperatures, resulting from the wavier Cu surface. Furthermore, the hBN film is grown by the inductively coupled plasma-enhanced CVD (ICP-CVD) and its growth mechanism is compared with that of CVD hBN. The growth rate of ICP-CVD hBN is 50 times faster than that of CVD hBN due to more energetic B and N species caused by plasma. The growth mechanism of ICP-CVD hBN without a long incubation time is dominated by nucleation.

Effects of Substrates on Nucleation, Growth and Electrical Property of Vertical Few-Layer Graphene.

A key common problem for vertical few-layer graphene (VFLG) applications in electronic devices is the solution to grow on substrates. In this study, four kinds of substrates (silicon, stainless-steel, quartz and carbon-cloth) were examined to understand the mechanism of the nucleation and growth of VFLG by using the inductively-coupled plasma-enhanced chemical vapor deposition (ICPCVD) method. The theoretical and experimental results show that the initial nucleation of VFLG was influenced by the properties of the substrates. Surface energy and catalysis of substrates had a significant effect on controlling nucleation density and nucleation rate of VFLG at the initial growth stage. The quality of the VFLG sheet rarely had a relationship with this kind of substrate and was prone to being influenced by growth conditions. The characterization of conductivity and field emissions for a single VFLG were examined in order to understand the influence of substrates on the electrical property. The results showed that there was little difference in the conductivity of the VFLG sheet grown on the four substrates, while the interfacial contact resistance of VFLG on the four substrates showed a tremendous difference due to the different properties of said substrates. Therefore, the field emission characterization of the VFLG sheet grown on stainless-steel substrate was the best, with the maximum emission current of 35 µA at a 160 V/μm electrostatic field. This finding highlights the controllable interface of between VFLG and substrates as an important issue for electrical application.

Plasma-Enhanced Chemical Vapor Deposition of Silicon Films at Low Pressure in GEC Reference Cell

A self-consistent fluid simulation of inductively coupled plasma-enhanced chemical vapour deposition (ICP-CVD) using silane, argon, and hydrogen mixture is presented. The model solves the continuity equations for charged species, the drift-diffusion equations to describe their transport and the electron energy balance equation, coupled with Maxwell’s and Poisson’s equations, using COMSOL Multiphysics software. In order to obtain a better comprehending of the discharge parameters, a discharge in a Gaseous Electronics Conference cell (GEC) reactor is simulated. In this study, the GEC reactor with five-turn inductive coils is driven at a radio frequency of 13.56 MHz in order to sustain the plasma discharge at low temperature for a mixture of SiH4/Ar/H2, with an intial gas pressure fixed at 20 mTorr. The simulations yield the profile of plasma components such as electron density and temperature as well as the electrical potential in the centre of the discharge during silicon films deposition. The effects of external settings, such as chamber pressure, applied power and hydrogen dilution, on the growth rate of the silicon films deposited by ICP-CVD are then investigated. It is shown that the increase of the applied power from 1000 to 3000 W and the gas pressure from 10 to 40 mTorr results in a moderate increase in the deposition rate of the silicon films, whereas the increase in the dilution of the hydrogen in the mixture produces its decrease.

Synthesis of vertical graphene nanowalls by cracking n-dodecane using RF inductively-coupled plasma-enhanced chemical vapor deposition

A facile and controllable one-step method to treat liquid hydrocarbons and synthesize vertical graphene nanowalls has been developed by using the technique of inductively-coupled plasma-enhanced chemical vapor deposition for plasma cracking of n-dodecane. Herein, the morphology and microstructure of solid carbon material and graphene nanowalls are characterized in terms of different operating conditions, i.e. input power, H2/Ar ratio, injection rate and reaction temperature. The results reveal that the optimal operating conditions were 500 W, 5:10, 30 μl min−1 and 800 °C for the input power, H2/Ar ratio, injection rate and reaction temperature, respectively. In addition, the degree of graphitization and the gaseous product are analyzed by Raman spectroscopy and gas chromatography detection. It can be calculated from the Raman spectrum that the relative intensity of ID/IG is approximately 1.55, and I2D/IG is approximately 0.48, indicating that the graphene prepared from n-dodecane has a rich defect structure and a high degree of graphitization. By calculating the mass loading and detecting the outlet gas, we find that the cracking rate of n-dodecane is only 6%–7% and that the gaseous products below C2 mainly include CH4, C2H2, C2H4, C2H6 and H2. Among them, the proportion of hydrogen in the outlet gas of n-dodecane cracking ranges from 1.3%–15.1% under different hydrogen flows. Based on our research, we propose a brand new perspective for both liquid hydrocarbon treatment and other value-added product syntheses.

Super-Capacitive Performance of Manganese Dioxide/Graphene Nano-Walls Electrodes Deposited on Stainless Steel Current Collectors.

Graphene nano-walls (GNWs) are promising materials that can be used as an electrode in electrochemical devices. We have grown GNWs by inductively-coupled plasma-enhanced chemical vapor deposition on stainless steel (AISI304) substrate. In order to enhance the super-capacitive properties of the electrodes, we have deposited a thin layer of MnO2 by electrodeposition method. We studied the effect of annealing temperature on the electrochemical properties of the samples between 70 °C and 600 °C. Best performance for supercapacitor applications was obtained after annealing at 70 °C with a specific capacitance of 104 F·g−1 at 150 mV·s−1 and a cycling stability of more than 14k cycles with excellent coulombic efficiency and 73% capacitance retention. Electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge measurements reveal fast proton diffusion (1.3 × 10−13 cm2·s−1) and surface redox reaction after annealing at 70 °C.

Static and dynamic performance of bistable MEMS membranes

This paper reports on the characteristic behaviour of bistable MEMS membranes before, during and after switching between the two ground states. For this purpose, silicon membranes with a diameter in the range of 300–800 μm and a thickness in the range of 2–5 μm were investigated. To achieve bistability, hydrogenated amorphous silicon carbide layers with different thicknesses in the range of 50 nm–400 nm were deposited on the silicon membranes using an inductively-coupled plasma-enhanced chemical vapour deposition process. With this bi-layered approach, an initial deflection of 2.5–8.1 μm was achieved which results in a total switching displacement of 5–16.2 μm A setup for bulge testing in combination with a Whitelight interferometer was used to analyse the membrane behaviour before the bi-stable switching. The pressure difference required to initiate switching between the ground states was in the range of 20–320 mbar. Both parameters (i.e. static deflection and switching pressure) are in excellent agreement with an analytical model. When increasing the pressure the membranes deflect up to 2.4 μm before switching, strongly depending on the diameter of the membranes. The dynamic measurements with the laser Doppler vibrometer showed switching times in the range of 5–20 μs, maximum velocities in the range of 1.5 to 4.3 m∙s−1 and high maximum accelerations between 2 to 11∙106 m∙s-2 depending on membrane properties such as diameter, thickness and mechanical stress. Finally, with fast Fourier transform analyses of the measured velocity signal characteristics Eigenmodes of the membrane are determined dominating the oscillation behaviour after switching, thus indicating approaches for effective damping with integrated actuators.

Co-synthesis of vertical graphene nanosheets and high-value gases using inductively coupled plasma enhanced chemical vapor deposition

One-step controllable synthesis of vertical graphene nanosheets (VGs) and high-value gases was achieved using inductively coupled plasma enhanced chemical vapor deposition (ICPECVD). The basic physical properties of the ICPECVD process were revealed via electrical diagnosis and optical emission spectroscopy. The coil current and voltage increased linearly with the augmenting of injected power, and CH, C2, H2 and H were detected at a wavelength from 300 to 700 nm, implying the generation of abundant graphene-building species. The morphology and structure of solid carbon products, graphene nanosheets, were systemically characterized in terms of the variations of operating conditions, such as pressure, temperature, gas proportion, etc. The results indicated that an appropriate operating condition was indispensable for the growth process of graphene nanosheets. In the present work, the optimized result was achieved at the pressure, heating temperature, applied power and gas proportion of 600 mTorr, 800 °C, 500 W and 20:20:15, respectively, and the augmenting of both CH4 and H2 concentrations had a positive effect on the etching of amorphous carbon. Additionally, H2 and C2 hydrocarbons were detected as the main exhaust gases. The selectivity of H2 and C2H2, measured in exhaust gases, reached up to 52% and 8%, respectively, which implied a process of free radical reactions and electron collision dissociation. Based on a comprehensive investigation of spectral and electrical parameters and synthesized products, the reaction mechanism of collision, dissociation, diffusion, etc, in ICPECVD could be speculated, providing a probable guide for experimental and industrial applications.

Synthesis of carbon nanowalls from a single-source metal-organic precursor.

In this work, the deposition of carbon nanowalls (CNWs) by inductively coupled plasma enhanced chemical vapor deposition (ICP-PECVD) is investigated. The CNWs are electrically conducting and show a large specific surface area, which is a key characteristic to make them interesting for sensors, catalytic applications or energy-storage systems. It was recently discovered that CNW films can be deposited by the use of the single-source metal-organic precursor aluminium acetylacetonate. This precursor is relatively unknown in combination with the ICP-PECVD deposition method in literature and, thus, based on our previous publication is further investigated in this work to better understand the influence of the various deposition parameters on the growth. Silicon, stainless steel, nickel and copper are used as substrate materials. The CNWs deposited are characterized by scanning electron microscopy (SEM), Raman spectroscopy and Auger electron spectroscopy (AES). The combination of bias voltage, the temperature of the substrate and the substrate material had a strong influence on the morphology of the graphitic carbon nanowall structures. With regard to these results, a first growth model for the deposition of CNWs by ICP-PECVD and aluminium acetylacetonate is proposed. This model explains the formation of four different morphologies (nanorods as well as thorny, straight and curled CNWs) by taking the surface diffusion into account. The surface diffusion depends on the particle energies and the substrate material and thus explains the influence of these parameters.

Light‐Induced Reversible Optical Properties of Hydrogenated Amorphous Silicon: A Promising Optically Programmable Photonic Material

Reversible optical properties (refractive index, n, and extinction coefficient, k) upon light soaking and annealing are predicted to originate from the metastable properties of hydrogenated amorphous silicon (a‐Si:H). Optically programmable photonic devices can be demonstrated when a‐Si:H is established as a potential programmable photonic material. Therefore, the effects of prolonged high intensity light soaking and annealing are investigated. A set of a‐Si:H films is deposited by inductively coupled plasma‐enhanced chemical vapor deposition (ICP‐PECVD) near the amorphous/nano‐crystalline phase transition that have significantly different hydrogen content and microstructures. Spectroscopic ellipsometry shows that the imaginary part of the pseudo dielectric function <ϵ2> values near the peak clearly decreases after light soaking and this decrease can be reversed after annealing. No loss of Si‐bonded hydrogen is observed after repeated cycles of light soaking and annealing and an inverse correlation between this reversibility and the hydrogen content is found. A change in the bulk optical properties is likely the main contributor to the observed metastable effect, suggesting a reversible refractive index change. Repeated cycles of reversible <ϵ2> behavior are demonstrated which together with the magnitude of reversibility (as high as 3.7% at 3.6 eV) illustrates the potential of a‐Si:H for future programmable photonic devices.

P‐229: Late‐News Poster: Flexible Barrier Layer to Prevent Silver Mesh Transparent Conductive Films from Electrochemical Migration

Electrochemical migration (ECM) in silver (Ag) mesh transparent conductive films (TCFs) was evaluated by thermal humidity bias (THB) and water drop (WD) tests, showing color change and dendrites formation at the unprotected electrode gaps. Flexible barrier layer deposited by low temperature inductively coupled plasma enhanced chemical vapor deposition (IC‐PECVD) process was applied to prevent Ag mesh TCFs from ECM. The barrier layer structure was organosilicon/SiOx pairs deposited with the mixture of HMDSO, O2 and Ar at different ratios in the same PECVD chamber. The study indicated that the ECM behavior of Ag mesh can be well suppressed by the barrier layer at water vapor transmission rate (WVTR) of 8.8×10‐3g/m2/day.

Growth of nanotubes using IC-PECVD as benzene carbon carrier

The main objective of this journal paper is to grow vertically aligned carbon nanotubes (CNTs) by using the method of inductively coupled plasma enhanced chemical vapor deposition (IC-PECVD) and to study their pattern of growth and specific properties. Benzene was tested in combination with Ni film as well as ferrocene in solution as catalyst to grow nanotubes. Different substrates were also used to check the effects of substrate on the synthesis of nanotubes. Various conditions and parameters were used for the synthesis purpose. Results obtained with benzene were promising for the formation of vertically aligned carbon nanotubes in the investigated parameter range. Results has been confirmed using SEM (scanning electron microscope), EDX (energy-dispersive X-ray) and Raman spectroscopy.

Field Emission from Titanium-Coated Carbon Nanotubes Grown on Micron-Sized Silicon Pillar Arrays

Carbon nanotubes (CNTs) have attracted great attention because of their unique physical properties such as high mechanical strength, thermal stability and electrical properties[1]. Because CNTs have high electron emission efficiency at low voltage due to their high aspect ratio, CNTs have been regarded as the most efficient electron emitter among various materials such as metal, semiconductor. However, the electric-field-screening effect of the dense CNTs and relatively high work function of CNTs (~ 5 eV) degrades the emission performance significantly[2,3]. CNTs grown on uneven substrate can reduce electric-field-screening effect and coating of CNTs with lower work function leads to enhanced field emission. In particular, it is reported that the coating Titanium (Ti) on CNTs affects the work function and the substantial change in surface morphology of CNTs most significantly[4].In this paper, we report the combined effect of suppression of electric-field-screening and lower work function on field emission characteristics by Ti-coated CNTs on micron-sized silicon (Si) pillar arrays. Micron-sized Si pillar arrays are formed using conventional photolithography process including reactive ion etching by mixture gas of SF6 and Ar. CNTs are grown on Invar(52% Fe-42% Ni-6% Co alloy) catalyst using C2H2 as a source gas by inductively-coupled plasma-enhanced chemical vapor deposition. Then, Ti with 5 nm thickness is optionally coated on CNTs by sputtering method and field emission behaviors are investigated in a diode configuration in the vacuum of ~10-7 Torr.Field enhancement factor for CNTs on Si pillar arrays was higher by 15% compared with that of CNTs on Si. The application of Ti on CNT surface reduced turn-on field by 30% further compared with that of pristine CNTs. In addition, coating of CNTs also improved emission stability by strengthening the adhesion between CNTs and substrate. We expect that the Ti-coated CNTs grown on micron-sized silicon pillar arrays can be excellent electron sources, providing a very stable current at very low fields by reduction of electric-field-screening effect and effective work function of emitters..

Inductively-coupled plasma-enhanced chemical vapour deposition of hydrogenated amorphous silicon carbide thin films for MEMS

In this study, the impact of various deposition parameters such as the reactive gas flow ratio, plasma power, substrate temperature and chamber back pressure of ICP-CVD deposited a-SiC:H thin films is investigated and the influence on important MEMS-related properties like residual stress, Young’s modulus, hardness, mass density and refractive index is evaluated. Basically, tailoring of the as-deposited a-SiC:H characteristics is possible to a great extent with residual stress values ranging from −16 up to −808MPa, Young’s modulus values between 36 and 209GPa or deposition of layers with hardness values ranging from 5.3 to 27.2GPa is feasible. Especially the mechanical parameters are strongly linked to both the SiC bond density and the amount of incorporated hydrogen obtained from Fourier transform infrared spectroscopy analyses.

High temperature annealing effects on the chemical and mechanical properties of inductively-coupled plasma-enhanced chemical vapor deposited a-SiC:H thin films

This paper reports the impact of thermal annealing up to temperatures of 1200°C on the chemical and mechanical properties of hydrogenated amorphous silicon carbide (a-SiC:H) thin films. These layers were deposited using an inductively-coupled plasma-enhanced chemical vapor deposition process with methane, silane and argon as precursor gases. The results of mass effusion measurements up to 1000°C are presented and the temperature-dependent effusion characteristics are compared to changes in the Fourier-transform infrared spectra. Furthermore, a simple method is presented that enables us to detect the onset of nanocrystallization in the a-SiC:H films caused by the high temperature annealing. The changes in chemical and crystallographic properties are discussed and related to the mechanical thin film properties, such as a substantial increase in Young's modulus from 176 up to 267GPa, in hardness from 24 up to 34.5GPa, as well as in residual film stress from −683 up to +3800MPa. Additionally, the decrease in layer thickness to about 70% of the initial value and the increase in refractive index from 2.33 to 2.78 are explained.

Investigation of amorphous SiOx layer on gold surface for Surface Plasmon Resonance measurements

The present study demonstrates that thin layers of amorphous silicon oxide (SiOx) grown by inductively-coupled plasma enhanced chemical vapor deposition (ICPECVD) technology at lower temperatures can be successfully combined with biosensors. In particular, gold-amorphous silica (Au/SiOx) interfaces were investigated for their potential applications as a low-cost Surface Plasmon Resonance (SPR) sensor chip. ICPECVD silicon dioxide films up to 25nm-thick were deposited at different pressure. Details of the SiOx thin layer properties in terms of refractive index, deposition rate, roughness, chemical bonds, Si2p and O1s bending energies, residual stress and contact angle were studied. The refractive index was found to decrease with increasing pressure for all the films. The depositions rates were lower for films deposited at higher pressures. We report here on the fabrication and characterization of stable and good reliabilities of SiOx deposited at two temperature 80°C and 130°C at pressures ranging from 2Pa to 20Pa. The results show that the SPR responses were very sensitive to any changes in the deposition parameters. In this study, we have shown that SiOx has good potential for further developments, as a wideband biosensor application with a higher sensitivity in SPR response.

Laser annealing of SiO2 film deposited by ICPECVD for fabrication of silicon based low loss waveguide

Laser annealing of silicon dioxide (SiO2) film formed by inductively coupled plasma enhanced chemical vapor deposition (ICPECVD) is studied for the fabrication of low loss silicon based waveguide. The influence of laser annealing on ICPECVD-deposited SiO2 film is investigated. The surface roughness, refractive index, and etch rate of annealed samples are compared with those of SiO2 film obtained by thermal oxidation. It is demonstrated that the performance of ICPECVD-deposited SiO2 film can be significantly improved by laser annealing. Al2O3/SiO2 waveguide has been fabricated on silicon substrate with the SiO2 lower cladding formed by ICPECVD and laser annealing process, and its propagation loss is found to be comparable with that of the waveguide with thermally oxidized lower cladding.

Study on the Characteristics of ICP-PECVD Boron Silicate Glasses Dependent on Diborane Flux

Boron silicate glasses from inductively-coupled plasma-enhanced chemical vapor deposition are investigated by variation of the diborane flux applied during deposition. Fast Fourier transform infrared spectroscopy measurements of B related peaks calibrated by inductively-coupled optical emission spectroscopy is used to determine the B concentration in the deposited films. Optical, chemical, and electric properties of the boron silicate glasses before and after a high temperature step, as well as of the resulting emitter layer, are discussed. Changes in the molecular composition of the B related bonding structure of the films during the high temperature step are found to be responsible for the properties of the emitter layers as well as the boron silicate glass films. Three corresponding regimes of the film growth depending on the diborane flux are identified and characterized. The formation of a boron-rich layer (BRL) is indirectly shown to be the limiting factor for emitter functions and influencing the corresponding properties under given conditions, i.e., at higher diborane fluxes.

Vertically aligned Si nanocrystals embedded in amorphous Si matrix prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD)

Abstract Vertically-aligned nanostructured silicon films are deposited at room temperature on p-type silicon wafers and glass substrates by inductively-coupled, plasma-enhanced chemical vapor deposition (ICPCVD). The nanocrystalline phase is achieved by reducing pressure and increasing RF power. The crystalline volume fraction ( X c ) and the size of the nanocrystals increase with decreasing pressure at constant power. Columnar growth of nc-Si:H films is observed by high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The films exhibit cauliflower-like structures with high porosity that leads to slow but uniform oxidation after exposure to air at room temperature. Films deposited at low pressures exhibit photoluminescence (PL) signals that may be deconvoluted into three distinct Gaussian components: 760–810, 920–935, and 990–1000 nm attributable to the quantum confinement and interface defect states. Hydrogen dilution is manifested in significant enhancement of the PL, but it has little effect on the nanocrystal size and X c .

Investigation of ICPECVD Silicon Nitride Films for HgCdTe Surface Passivation

In this paper, we report results of a study of SiN x thin films for surface passivation of HgCdTe epitaxial layers. The hydrogenated amorphous SiN x films under study were deposited by a SENTECH SI500D inductively coupled plasma-enhanced chemical vapor deposition (ICPECVD) system with a high-density and low-ion-energy plasma source at relatively low substrate temperatures (80°C to 100°C). A series of SiN x films were first deposited on CdTe/GaAs and Si substrates under different deposition conditions to examine the influence of ICP power, deposition temperature, and NH3/SiH4 ratio on properties of the SiN x films. To investigate SiN x deposition conditions suitable for surface passivation of HgCdTe, the SiN x /n-Hg0.68Cd0.32Te interface characteristics were investigated employing capacitance–voltage measurements, and the corresponding interface trap densities D it were extracted from the high-frequency and low-frequency characteristics. Analysis of SiN x /n-Hg0.68Cd0.32Te metal–insulator–semiconductor (MIS) structures indicated that Si-rich SiN x films deposited at 100°C by ICPECVD exhibit electrical characteristics suitable for surface passivation of HgCdTe-based devices, that is, interface trap densities in the range of mid-1010 cm−2 eV−1 and fixed negative interface charge densities of ∼1011 cm−2. In addition, the relationship between bond concentration and surface passivation performance has been explored based on infrared (IR) absorbance spectra. The Si–H and N–H bond concentrations were found to be directly correlated with passivation performance, such that SiN x films with a combination of high [Si–H] and low [N–H] bond concentrations were found to be suitable as electrical passivation layers on HgCdTe.

Impact of auxiliary capacitively coupled plasma on the properties of ICP-CVD deposited a-SiNx:H thin films

In this study, we report on the properties of amorphous hydrogenated silicon nitride (a-SiNx:H) thin films synthesized by inductively coupled plasma enhanced chemical vapour deposition (ICP-CVD), combined with an auxiliary capacitively coupled plasma excitation. Physical properties, such as the deposition rate, refractive index and film stress, as well as the chemical composition, microstructure and etch resistance of the samples were investigated. Depending on the capacitively coupled plasma power PRF, two regions can be distinguished which are dominated either by an increased generation of plasma radicals or by an enhanced ion bombardment. At PRF=35W, a maximum in the deposition rate is observed as well as an abrupt change in the chemical composition, resulting in an extremely high (>2.5GPa) compressive stress, in comparison to the layers deposited with PRF=0. In addition, the wet etch rate in hydrofluoric acid (HF) decreases substantially. Above, up to PRF=150W, ion bombardment of the growing film surface is more pronounced due to an increased self-bias of the substrate decreasing the effective deposition rate. Fourier-transform infrared spectroscopy measurements indicate that this behaviour is in close relation to the NH bond density in the samples. Additionally, the continuous increase of the refractive index and SiH bond density, accompanied by the redshift of the SiN infrared absorption peak show that with higher PRF the Si content of the films increases.