Coupled Plasma Chemical Vapor Deposition Research Articles

Silicon-based electrochemical microdevices for silicate detection in seawater

This paper describes the electrochemical characterisation of gold and platinum microdevices mass fabricated using silicon technology. Specific attention was paid to allow in situ electrochemical detection of silicate in seawater. Thus, using a silicon nitride (Si3N4) inorganic passivation layer patterned using Inductively Coupled Plasma Chemical Vapor Deposition (ICP-CVD), coupled with a non-aggressive lift-off based process, different electrodes were isolated electrically: one gold or platinum working electrode named “macroelectrode” (2mm of diameter), four gold or platinum working ultramicroelectrodes (UME) (15μm of diameter), one platinum counter electrode and one silver electrode which can be used as a reference electrode after its chlorination. Their small size and mass fabrication make them very promising for oceanographic applications. As some components of microdevices release silicate and contaminate the solution, after being immersed in seawater, these microdevices were inserted in a specific cell that only puts the electrodes in contact with the seawater solution. Gold has been tested as a possible material for working electrodes but its lack of adherence to the passivation layer in seawater solutions led to non-accurate measurements. On the contrary, passivation layer on platinum electrodes resists to the seawater corrosive medium. The analytical performances of the platinum microdevices has been tested through different silicate calibrations and shows an outstanding accuracy and reproducibility when measurements are performed, especially with the macroelectrodes which showed only 2.8% signal variation after four months of use and a limit of quantification of 0.50μmolL−1 suitable for oceanographic applications.

Characterization of low temperature graphene synthesis in inductively coupled plasma chemical vapor deposition process with optical emission spectroscopy.

Low-temperature graphene was synthesized at 400 degrees C with inductively coupled plasma chemical vapor deposition (PECVD) process. The effects of plasma power and flow rate of various carbon containing precursors and hydrogen on graphene properties were investigated with optical emission spectroscopy (OES). Various radicals monitored by OES were correlated with graphene film properties such as sheet resistance, I(D)/I(G) ratio of Raman spectra and transparency. C2H2 was used as a main precursor and the increase of plasma power enhanced intensity of carbon (C2) radical OES intensity in plasma, reduced sheet resistance and increased transparency of graphene films. The reduced flow rate of C2H2 decreased sheet resistance and increased transparency of graphene films in the range of this study. H2 addition was found to increase sheet resistance, transparency and attributed to reduction of graphene grain and etching graphene layers. OES analysis showed that C2 radicals contribute to graphite networking and sheet resistance reduction. TEM and AFM were applied to provide credible information that graphene had been successfully grown at low temperature.

Nanocrystalline Si:H films made by inductively coupled plasma using internal low inductance antenna

P-type hydrogenated nanocrystalline silicon (nc-Si:H) thin films are prepared on glass substrate by an inductively coupled plasma chemical vapor deposition system using multiple internal low inductance antenna units. The deposition rate as well as the microstructural and electrical properties of the nc-Si:H films are investigated systematically as functions of hydrogen dilution, discharge power and working distance. The effects of various process parameters are identified and rationalized. The applicability of this type of high density plasma to manufacture nc-Si:H films is critically assessed.

The 1/f noise characteristics of In0.83Ga0.17As photodiodes with SiNx passivation films fabricated by two different techniques

The 1/f noise characteristics of In0.83Ga0.17As photodiodes have been studied in this work. The surface SiNx passivation films of photodiodes are fabricated by plasma enhanced chemical vapor deposition (PECVD) and inductively coupled plasma chemical vapor deposition (ICPCVD), respectively. The noise measurements are performed at variable reverse bias and temperature for different area diodes. The results show that ICPCVD passivation improves the surface quality and suppresses the 1/f noise significantly compared to PECVD passivation. The 1/f noise has an exponential relationship with reverse bias between 0.1V and 0.5V at room temperature for the diodes passivated by PECVD while it is a power law relationship for the diodes passivated by ICPCVD. As the temperature dropping, the 1/f noise of the diodes passivated by ICPCVD decreases more rapidly at reverse bias 0.1V, which implies the advantage of ICPCVD passivation becomes more conspicuous at the lower temperature. According to the observed geometry dependence, the 1/f noise of the diodes passivated by PECVD dominantly originates from the perimeter, whereas it dominantly originates from the bulk and upper surface for the diodes passivated by ICPCVD.

Nano-mechanical properties of nano-gold/DLC composite thin films

Diamond-like-Carbon composite films, with embedded gold nanoparticles, were deposited onto glass substrates by using capacitively coupled plasma chemical vapour deposition (CCP-CVD) technique. The volume fraction of the metal nanoparticles in the films as well as the size of the nanoparticles was varied by varying the percentage of argon in the methane + argon mixture during the deposition. Bonding environments in these films were obtained from Raman and GIXRD. The nanomechanical and nanotribological properties of the Au-DLC nanocomposite films were evaluated. In situ SPM imaging was utilized to depict deformation characteristics developed during the static and dynamic contact events. Influence of metal incorporation on the extent of sp 2 / sp 3 hybridization and thereby on the nanomechanical and nanotribological properties of the DLC films was studied.

High Quality Inductively Coupled Plasma Chemical Vapor Deposited SiOxNy Gas Barrier Films for OLED Display

SiOxNy thin films were synthesized on polyethylene terephthalate (PET) substrate at low temperature (~40°C) by inductively coupled plasma chemical vapor deposition (ICP- CVD) system. Details of the RF power, gas ratio (Si, N2, O2, Ar, H2), and film thickness effects on the SiOxNy/PET film properties in terms of deposition rate, chemical composition, water vapor transmittance rate (WVTR), transmittance, refractive index, surface morphologies, defect, and residual stress were described. When the RF power increased from 500W to 1200W, the deposition rate and surface roughness increased while WVTR decreased to a value near 0.008g/m2/day which is very good WVTR property as a single inorganic barrier thin films. A lower WVTR value can be achieved under a barrier thickness of 300nm.

Characteristics of Poly-Si Thin Film Transistors with Highly Biaxially Oriented Linearly Arranged Poly-Si Thin Films Using Double Line Beam Continuous-Wave Laser Lateral Crystallization

Highly biaxially oriented linearly arranged poly-Si thin films were formed by double line beam continuous-wave laser lateral crystallization (DLB-CLC). Crystallinities of the poly-Si thin films were (110), (111), and (211) for the laser scan, transverse, and surface directions, respectively, and energetically stable Σ3 grains boundary were observed dominantly. Silicon grains were elongated in the laser scan direction and one-dimensionally very large silicon grains with lengths of more than 100 µm were fabricated. High-performance low-temperature poly-Si thin film transistors (TFTs) using these poly-Si thin films were fabricated at low temperature (≦550 o C) by a metal gate self-aligned process.The TFTs were fabricated as follows. A-Si of 150 nm thickness and cap SiO2 of 100 nm thickness were deposited on a quartz substrate. CW laser crystallization with double-line spot irradiation (wavelength: 532 nm, laser power: 8.5 W, scan speed: 0.25 cm/s) on a-Si was carried out, and lateral-crystallized poly-Si was formed. After the laser crystallization, the cap SiO2 was etched using buffered HF aqueous solution (BHF), and lithography and dry etching (Cl2: 40 sccm, HBr: 40 sccm) were performed in order to pattern the poly-Si active layer. Next, gate SiO2 of 50 nm thickness was deposited by inductively coupled plasma chemical vapor deposition (ICP CVD, SiH4: 0.6 sccm, O2: 10 sccm, Ar: 40 sccm) and a Mo gate electrode of 200 nm thickness was deposited by sputtering method. After lithography patterning, wet etching of Mo was carried out with a solution of H3PO4: HNO3: CH3COOH: H2O= 400: 25: 50: 25 and the gate electrode was formed. A self–aligned source and drain system was formed by As ion doping (ion dose: 2×1015 cm-2, acceleration voltage: 66 keV) using the Mo gate electrode as the mask. Activation annealing treatment was carried out at 550o C in N2 ambient for 30 min. A sacrificial oxide layer in the S/D region was removed using BHF. After the removal, 150-nm-thick interlayer insulation films were deposited by atmospheric pressure chemical vapor deposition (APCVD), and the contact hole was etched using BHF. A Mo metal pad was deposited by sputtering method, and finally sintering processing was carried out at 400 o C in H2ambient for 30 min. Figure 1 shows a microphotograph of the fabricated DLB-CLC poly-Si TFT.A TFT with a high electron field effect mobility of µFE= 560 cm2V-1s-1 in a linear region was realized. At the electron field effect mobility, its variation was within 10% at same crystallization region. High-performance TFTs with DLB-CLC were demonstrated, however it was found that off-leakage current was relatively large. The leakage current mechanism was investigated by measuring temperature dependence of the TFT characteristics. The field-effect mobilities at the ON region were proportional to T-1.5 as shown in Fig. 2. The result shows the phonon scattering was dominant as same as single silicon crystal. On the other hand, in the OFF region, the electrical conductivity shows logarithmic behavior as a function of exp{-EB/kBT} as shown in Fig. 3. This leakage current shows that there are many trap states in the grain boundaries.

Characteristics of room temperature silicon nitride deposited by internal inductively coupled plasma chemical vapor deposition.

The parallel inductively coupled plasma chemical vapor deposition system is used to directly control the activated radical and charged species in the plasma of a silicon nitride thin film, which is deposited at room temperature for flexible displays. By controlling the plasma characteristics of silicon nitride with plasma heating at 85 °C, this new technique produced low hydrogen content silicon nitride thin films at room temperature (25 °C). Deposition rates and refractive indices of the films ranged from 6.8 nm/min to 4.57 nm/min and from 2.125 to 1.749 with NH3 variation and ranged from 5.12 nm/min to 4.105 nm/min and from 1.81 to 1.92 with N2 variation, respectively. In the optical emission spectra of the plasmas investigated at fixed RF powers (1000 W), the peaks corresponding to the radical and charged species of SiH4, N2, and NH3 were related to the changes of the deposition rate and refractive index of the films. Current-voltage measurements with MIM capacitors revealed that these films had dielectric breakdown fields higher than 8 MV/cm, and FTIR showed their lower hydrogen contents than the conventional PECVD films.

Inductively coupled plasma chemical vapor deposition silicon nitride for passivation of In0.83Ga0.17As photodiodes

Silicon nitride films (SiNx) deposited by ICPCVD (inductively coupled plasma chemical vapor deposition) at lower temperature (75°C) are investigated on extended wavelength In0.83Ga0.17As photodiodes. Compared to SiNx films (330°C) grown by PECVD (plasma enhanced chemical vapor deposition), the low-temperature-deposited SiNx films grown by ICPCVD have a better effect on decreasing the dark current of In0.83Ga0.17As photodiodes. Area- and perimeter-dependent leakage current were separated by test arrays with different area photosensitive elements. The results indicate that the perimeter-dependent leakage current is obviously decreased for the devices passivated by ICPCVD. The analysis of activation energy indicates that the area-dependent leakage current is dominated by diffusion and generation-recombination mechanisms at reverse bias of 0.1–0.5V and temperature of 260–300K for both ICPCVD and PECVD processes. At reverse bias of 0.1–0.5V and temperature of 200–300K the perimeter-dependent leakage current is dominated by surface recombination current mechanism for ICPCVD, while it is dominated by ohmic current and surface recombination current mechanisms for PECVD. The cause of the reduction of perimeter-dependent leakage current for ICPCVD may derive from its better restraint of ohmic current.

Fast and simultaneous growth of graphene, intermetallic compounds, and silicate on Cu–Ni alloy foils

A graphene bilayer was grown on copper–nickel alloy foils (30 at-% Ni: 70 at-% Cu designated as a 30Ni–70Cu) via an inductively coupled plasma–chemical vapor deposition chamber, and was characterized. The first layer fully covered the foil, while there was partial coverage of the second layer. At the same time, the alloy catalyst produced a compound of magnesium silicate in some regions and of copper sulfide in other regions on which a graphene monolayer simultaneously grew without any discontinuity or boundaries of the 1st graphene monolayer between simultaneous growth and graphene-only growth regions. Compared with Cu foils, the alloy foils led to faster growth of the graphene film in graphene-only growth regions, while maintaining the same quality, homogeneity, and thickness uniformity as a monolayer graphene grown on Cu. Raman spectroscopy and scattering demonstrated that the 2D and D bands of the Raman spectra were in the same position for the monolayer graphene on 30Ni–70Cu regardless of the grown regions and for the graphene on the Cu with a full width at half maximum of ∼38 cm−1 ranging from 30 to 55 cm−1 of 2D, and without a D band in the spectra of the graphene monolayer and bilayer. Thus the resulting graphene growth is affected primarily by the Cu catalyst, partly by the compounds grown simultaneously with the graphene monolayer on the foil surface via thermal reactions of the impurities dissolved in the alloy matrix, and partly by the Ni. The quality of the graphene is dependent on the major composition of Cu catalyst in the alloy foils. On the other hands, the alloying element of Ni governs the growth kinetics unless the alloy foils is covered with the intermetallic compounds and silicate.

Graphene film growth on sputtered thin Cu–Ni alloy film by inductively coupled plasma chemical vapor deposition

Graphene film growth on a Cu–Ni alloy thin film with various alloy compositions is reported in this paper.

Correlation Between Arrhenius Equation and Binding Energy by X-ray Photoelectron Spectroscopy

SiOC films were prepared by capacitively coupled plasma chemical vapor deposition, and the correlation between the binding energy by X-ray photoelectron spectroscopy and Arrhenius equation for ionization energy was studied. The ionization energy decreased with increase of the potential barrier, and then the dielectric constant also decreased. The binding energy decreased with increase of the potential barrier. The dielectric constant and electrical characteristic of SiOC film was obtained by Arrhenius equation. The dielectric constant of SiOC film was decreased by lowering the polarization, which was made from the recombination between opposite polar sites, and the dissociation energy during the deposition. The SiOC film with the lowest dielectric constant had a flat surface, which depended on how carbocations recombined with other broken bonds of precursor molecules, and it became a fine cross-linked structure with low ionization energy, which contributed to decreasing the binding energy by Si 2p, C 1s electron orbital spectra and O 1s electron orbital spectra. The dielectric constant after annealing decreased, owing to the extraction of the <TEX>$H_2O$</TEX> group, and lowering of the polarity.

Neural Network Modeling of Deposition Rate Characteristics of Low Temperature Silicon Nitride Deposited by Inner Two Parallel Coil Inductively Coupled Plasma Chemical Vapor Deposition

In this study, a neural network model for silicon nitride (SiN) deposition process is proposed. SiN thin films were deposited by a direct inner two parallel inductively coupled plasma chemical vapor deposition (ICPCVD) system that can control the activated radical and charged species in plasma. This system can produce SiN thin films at low temperature for flexible displays. The input parameters considered for deposition conditions were the N2 gas flow rate, NH3 gas flow rate, and substrate temperature. These were varied within the ranges of 0-20 sccm, 0-20 sccm, and 100-300 degrees C, respectively. For those of input parameters and the output of deposition rate, we developed a back propagation neural network model with a pre-processor. It is shown that the model accuracy and learning speed of the proposed model are better than those of a conventional neural network model. In the experiments conducted, it was found that the deposition rate increased as the flow rates of ammonia (NH3) and nitrogen (N2) increased up to a certain amount. On the contrary, when the flow rates of NH3 and N2 went over a certain amount, the deposition rate decreased. It was also found that an increase in temperature resulted in an increase in the deposition rate.

Double-metal-gate nanocrystalline Si thin film transistors with flexible threshold voltage controllability

We fabricated nano-crystalline Si (nc-Si:H) thin-film transistors (TFTs) with a double-metal-gate structure, which showed a high electron-mobility (μFE) and adjustable threshold voltages (Vth). The nc-Si:H channel and source/drain (S/D) of the multilayered TFT were deposited at 375 °C by inductively coupled plasma chemical vapor deposition. The low grain-boundary defect density of the channel layer is responsible for the high μFE of 370 cm2/V-s, a steep subthreshold slope of 90 mV/decade, and a low Vth of −0.64 V. When biased with the double-gate driving mode, the device shows a tunable Vth value extending from −1 V up to 2.7 V.

Improvement of photoluminescence from Ge layer with patterned Si3N4 stressors

Lattice strain applied by patterned Si3N4 stressors in order to improve the optical properties of Ge layers directly grown on a Si substrate was investigated. Patterned Si3N4 stressors were fabricated by various methods and their effects on the strain and photoluminescence were studied. Although we found that when the stressor was fabricated by thermal chemical vapor deposition (CVD), the Ge waveguide was tensilely and compressively strained in the edge and center positions, respectively, and photoluminescence (PL) could be improved by decreasing the width of the waveguide, the crystallinity of the Ge waveguide was degraded by the thermal impact of the deposition process. Low-temperature methods were therefore used to make the patterned stressors. The tensile strain of the Ge layer increased from 0.14% to 0.2% when the stressor was grown by plasma enhanced CVD at 350°C, but the effects of the increased tensile strain could not be confirmed because the Si3N4 layer was unstable when irradiated with the excitation light used in photoluminescence measurements. Si3N4 stressors grown by inductively coupled plasma CVD at room temperature increased the tensile strain of the Ge layer up to 0.4%, thus red-shifting the PL peak and obviously increasing the PL intensity. These results indicate that the Si3N4 stressors fabricated by the room-temperature process efficiently improve the performance of Ge light-emitting devices.

Electrical and Mechanical Characteristics of Room Temperature Deposited Silicon Nitride Using Two Inner Parallel Cylindrical Coils Inductively Coupled Plasma Chemical Vapor Deposition

For investigating silicon nitride (SiN) thin film deposition process at room temperature without additional substrate heating, we studied inductively coupled plasma chemical vapor deposition with two inner parallel cylindrical coils which can activate the more radicals and charged species in the plasma. We investigated the influence of plasma RF power on the characteristics of room temperature deposited SiN films. Deposition rates, dielectric constant, refractive index, and stress of the films ranged from 4.5 nm/min to 8.3 nm/min, 8.4 to 10, 1.8 to 2.1, and 0.54 to 0.15, respectively. According to the FTIR measurements, the concentration of the Si--H and N--H bonds was decreased as the RF power increased, and the Si--H bonds tended to disappear at RF power over 500 W. This reduction in the hydrogen content was accompanied by the increases in the deposition rate and refractive index. It was confirmed that the breakdown field could be also maximized to 10 MV/cm.

Electrical transport phenomena prevailing in undoped nc-Si/a-SiNx:H thin films prepared by inductively coupled plasma chemical vapor deposition

A comprehensive analysis on the electrical transport phenomena prevailing in undoped nc-Si/a-SiNx:H thin films prepared by inductively coupled plasma chemical vapor deposition and its correlation with the specific inhomogeneous structure, consisting of a mixture of different phases involving charge transfer by tunneling and thermionic emission or a connected network of aggregates of such components, has been made for deeper understanding in order to facilitate and improve the device applicability of the material. The nc-Si/a-SiNx:H films exhibit a thermally activated electrical transport above room temperature. Multi-phonon hopping (MPH), following σ∝Ty, occurs below room temperature, involving higher number of acoustic phonons in less crystalline network at higher nitrogenation. In less nitrogenated network, the MPH conduction continues up to the lowest temperature because of less localization of charge carriers within larger size of the nanocrystallites. Mott variable range hopping (Mott-VRH), following ln(σ) ∝ T−¼, is in effect below a certain temperature for highly nitrogenated network. The nature of variations of Mott parameter, T*, hopping activation energy, Wh, optimum hopping distance, rh, and the estimated density of states at the Fermi level, N(EF), identify the increased degree of disorder in the film attributing enhanced amorphous concentration at higher nitrogenation. The transition from MPH to Mott-VRH occurring at higher temperature at relatively higher nitrogenation has been interpreted as the freezing out of the acoustic phonons associated with lower grain size with higher number density at comparatively higher temperature, considering the phonon wavelength approximately of the size of nanocrystallites. The present intrinsic nc-Si/a-SiNx:H material containing nanocrystallites of average size ∼12–2 nm and number density ∼1011–1012 cm−2 providing a significantly wide range of optical band gap, Eg ∼ 1.80–2.75 eV with associated very high electrical conductivity, σD ∼ 10−2–10−6 S cm−1 along with high carrier concentration, ne ∼ 1014–1011 cm−3 and electron mobility, μe ∼ 246–105 cm2 V−1 s−1, seems to be the superior, concerning issues related to usability in device fabrication, among typical wide optical gap silicon dielectric materials available in the literature, e.g., silicon carbide, silicon oxide, and amorphous silicon films with nc-Si inclusions; while being the only comprehensive report on nanocrystalline silicon nitride (nc-Si/a-SiNx:H) thin films, in particular.

A-IGZO TFTs With Inductively Coupled Plasma Chemical Vapor Deposited ${\rm SiO}_{x}$ Gate Dielectric

In this brief, amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) are fabricated at . Inductively coupled plasma chemical vapor deposition (ICP-CVD) is used to grow SiOx gate dielectric of the a-IGZO TFTs. The fabricated devices exhibit a high saturation mobility of 26.85 cm2/V·s, a steep subthreshold swing of 0.145 V/decade, and an ON/OFF current ratio of 2.3×107. Atomic force microscope and scanning electron microscope images show that the surface characteristics of the ICP-CVD SiOx gate dielectric are much superior to those of the conventional plasma-enhanced CVD SiOx. It is suggested that the superior surface characteristics of the ICP-CVD SiOx are the main origin of the high performance of the a-IGZO TFTs with the ICP-CVD SiOx gate dielectric.

Raman spectroscopy of silicon-nanocrystals fabricated by inductively coupled plasma chemical vapor deposition

Size dependent properties of nanostructures – quantum confinement effect, optical phonon confinement, multiexciton generation – prompted extensive research of good old silicon, at nanoscale dimensions, for potential applications in next generation device applications. However, for realizing functional devices, a thorough understanding of size related properties and a viable fabrication method are crucial. In this study, we present a thorough Raman analysis of silicon-nanocrystals (Si-NCs) of various sizes fabricated by inductively coupled plasma enhanced CVD (ICPCVD). Si-NCs were realized using a two-step process for tight size control; initially alternating multilayers of SiOx<2 (SRO) and SiO2 were deposited by ICPCVD, followed by high temperature annealing for phase-separation and crystallization. To study the optical phonon confinement, a series of five multilayer samples with thickness of SRO sublayer (TSRO) varying from 10nm to 2nm were fabricated. Raman spectra for ML samples with TSRO≥6nm exhibited three notable features; a red-shifted sharp peak compared to c-Si, a broad asymmetric shoulder on the lower frequency side and a grain boundary band related to the interface between Si-NCs and SiO2. These features confirm the formation of Si-NCs in SRO sublayers. ML samples with TSRO≤4nm showed incomplete crystallization indicating SRO thickness dependent crystallization. To further study this behavior, the degree of crystallization was quantified by estimating the crystalline volume fraction which was observed to decrease with decreasing TSRO. Red shift of the Raman peak, in accordance with the optical phonon confinement model, was used to estimate the size of Si-NCs. The sizes so obtained were observed to be in good agreement with the TSRO values. The study is relevant and encouraging for further understanding of Si-NC based composite material for various applications including next generation photovoltaics.

High-Quality ICPCVD $\hbox{SiO}_{2}$ for Normally Off AlGaN/GaN-on-Si Recessed MOSHFETs

We have developed a high-quality <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{SiO}_{2}$</tex></formula> deposition process using an inductively coupled plasma chemical vapor deposition system for use as a gate oxide of AlGaN/GaN-on-Si metal–oxide–semiconductor heterostructure field-effect transistor (MOSHFET) for power switching applications. A breakdown field of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim$</tex></formula> 12 MV/cm was achieved using the optimized deposition conditions that were successfully applied in fabrication of the normally off AlGaN/GaN-on-Si MOSHFETs. The fabricated device exhibited excellent characteristics: a maximum drain current density of 375 mA/mm, a threshold voltage of 3 V, and a breakdown voltage of 820 V.