Plasma-enhanced Chemical Vapor Deposition System Research Articles

非晶碳氮纳米尖端的微结构和发光机理

Carbon nitride nanotips were prepared on silicon substrate in plasma-enhanced hot filament chemical vapor deposition system,in which methane,hydrogen and nitrogen were used as the reaction gases.The carbon nitride nanotips were characterized by scanning electron microscopy and micro-Raman spectroscopy.The photoluminescence of the carbon nitride nanotips was measured at room temperature and the photoluminescence spectrum shows two emission bands at 406 and 506 nm.Combined with the Raman spectrum,the microstructure of the carbon nitride was analyzed.According to the structure and photoluminescence mechanism of amorphous carbon nitride films,the photoluminescence of carbon nitride nanotips was studied.

Development of Double-side SiC PECVD System for MEMS

This paper reports the development of a new double-side plasma-enhanced plasma chemical vapor deposition (PECVD) system for amorphous SiC. The PECVD system has cathode-coupling and hot wall type configuration. A wafer, which works as a cathode, is supported at the center of a quartz tube, and carbon anodes are placed at both sides of the wafer. Using tetramethylsilane (Si(CH3)4) mixed with H2 and Ar, amorphous SiC was deposited on both sides of the wafer simultaneously, and little wafer bending was observed even if the film has a compressive stress of several hundred MPa. Thus, the developed double-side PECVD system is useful to minimize wafer bending, which is often a problem for devices and fabrication processes. The fundamental properties (e.g. stress and Si/C ratio) of deposited films were investigated under different deposition conditions (e.g. gas flow rates and self-bias voltage).

The relationship of structural properties of microcrystalline silicon to solar cell performance

A study on the microstructure of intrinsic, microcrystalline silicon (μc-Si:H) layers deposited with various silane concentrations is presented. The layers were fabricated in a large-area Plasma-Enhanced Chemical Vapor Deposition (PECVD) system on rough TCO-coated substrates. The microstructure was investigated by Raman spectroscopy and X-ray diffraction (XRD) in two different geometries. The structural properties are related to the performance of solar cells deposited together with the μc-Si:H layers. The crystalline volume fraction of the studied films ranged from highly crystalline to amorphous as derived from Raman spectroscopy and Grazing Incidence XRD. A hexagonal silicon phase, which is related to stacking faults and twins appeared in Bragg–Brentano and Grazing Incidence diffractograms, and revealed that these types of defects occur more pronounced on crystal planes that grow parallel to the sample surface. By evaluating the integrated intensity ratio of the {220} to {111} reflection of cubic silicon a small preferential orientation (texture) was observed for the high-crystalline material. Material close to the transition to amorphous phase (that leads to an optimum in solar cell performance) exhibits no preferential orientation. This shows that for the material under investigation — which is optimized for tandem solar cell with efficiencies above 12% — a preferential orientation is not a requirement to achieve device-quality material for good solar cell performance.

Pulsed plasmas study of linear antennas microwave CVD system for nanocrystalline diamond film growth

Abstract

Effect of Nitrogen Doping on the Structure and Optical Properties of N-Type Hydrogenated Amorphous Silicon Thin Films

Hydrogenated amorphous silicon (a-Si:H) thin films doped with both Phosphor and Nitrogen are deposited by ratio frequency plasma enhanced chemical vapor deposition (PECVD). The effect of gas flow rate of ammonia (FrNH3) on the composition, microstructure and optical properties of the films has been investigated by X-ray photoelectron spectroscopy, Raman spectroscopy and ellipsometric spectra, respectively. The results show that with the increase of FrNH3, Si-N bonds appear while the short-range order deteriorate in the films. Besides, the optical properties of N-doped n-type a-Si:H thin films can be easily controlled in a PECVD system.

Carbon fractals grown from carbon nanotips by plasma-enhanced hot filament chemical vapor deposition

Carbon nanomaterials with different structures were prepared in a custom-designed plasma-enhanced hot filament chemical vapor deposition system using methane, hydrogen and nitrogen. They were investigated by scanning electron microscopy (SEM) and micro-Raman spectroscopy. The SEM images show that the smooth carbon nanotips are formed under a high bias current and the carbon fractals can grow from the tips of the carbon nanotips under a low bias current. The results of micro-Raman spectroscopy indicate that the graphitization of the carbon nanomaterials was improved by ion bombardment. Combined the ion bombardment, electric field enhancement and electron emission mechanisms, the formation model of the carbon fractals was suggested.

Room-temperature photoluminescence from nitrogenated carbon nanotips grown by plasma-enhanced hot filament chemical vapor deposition

Nitrogenated carbon nanotips with a low atomic concentration of nitrogen have been synthesized by using a custom-designed plasma-enhanced hot-filament plasma chemical vapor deposition system. The properties (including morphology, structure, composition, photoluminescence, etc.) of the synthesized nitrogenated carbon nanotips are investigated using advanced characterization tools. The room-temperature photoluminescence measurements show that the nitrogenated carbon nanotips can generate two distinct broad emissions located at ∼405 and ∼507 nm, respectively. Through the detailed analysis, it is shown that these two emission bands are attributed to the transition between the lone pair valence and σ* bands, which are related to the sp3 and sp2 C–N bonds, respectively. These results are highly relevant to advanced applications of nitrogenated carbon nanotips in light emitting optoelectronic devices.

Note: Continuous synthesis of uniform vertical graphene on cylindrical surfaces

This note describes a new reactor design for continuous synthesis of vertically oriented graphene (VG) sheets on cylindrical wire substrates using an atmospheric plasma-enhanced chemical vapor deposition (PECVD) system. Through combining a U-shaped reactor design with "dynamic mode" synthesis featuring simultaneous rotational and axial movements of the metallic wire substrate, the new setup can enable continuous synthesis of VG sheets on the wire surface with remarkable uniformity in both circumferential and axial directions. In contrast, synthesis of VG at "static mode" with a fixed substrate can only lead to non-uniform growth of VG sheets on the wire surface. Potential applications of the resulting uniform-VG-coated metallic wire could include field emitters, field-ionization-based neutral atom detectors, and indoor corona discharges.

Reactive Ion Etching of Carbon Nanowalls

Two-dimensionally standing graphene sheets, i.e., carbon nanowalls (CNWs), were synthesized on a Si substrate employing a capacitively coupled fluorocarbon plasma-enhanced chemical vapor deposition system together with H radical injection. To apply CNWs in electronic devices and/or membrane filters, we have demonstrated the reactive ion etching (RIE) of CNWs. RIE employing H2/N2 gases showed that the CNW films were anisotropically etched at a relatively high rate of more than 250 nm/min. However, the 10-nm-thick interface layer between a CNW film and the Si substrate remained and the interface layer was not completely etched. In contrast, RIE employing Ar/H2 gases enabled us to completely remove the interface layer. Ar/H2 RIE was also carried out from the bottom surface of CNW films after exfoliating them from the Si substrate. As a result, a free-standing CNW film of 550 nm thickness without an interface layer as a membrane filter was successfully formed.

Effects of H 2 plasma treatment on properties of ZnO:Al thin films prepared by RF magnetron sputtering

Al-doped ZnO (AZO) thin films were prepared on glass substrates by radio-frequency magnetron sputtering at deposition temperatures ranging from room temperature (RT) to 300 °C for transparent electrode applications. This study investigates the effects of H 2 plasma treatment on structural, electrical, and optical properties of AZO thin films. Plasma treatment was conducted at 300 °C using a plasma-enhanced chemical vapor deposition system for potential large size substrate applications. The crystal structure of plasma treated AZO films did not change considerably, but the surface roughness and surface grain size increased slightly. Improvement in electrical properties was strongly dependent on the deposition temperature. When the deposition temperature ranged from 300 °C to RT, the resistivity of plasma treated films decreased significantly by 22.7% to 97.6%, and the optical bandgap broadened by 0.011 to 0.076 eV.

Silicon precursor development for advanced dielectric barriers for VLSI technology

For back end of line (BEOL) interconnects, maintaining device reliability while scaling the dielectric stack is a continual challenge. In this paper, the ability to improve the dielectric barrier properties of silicon carbonitride (SiCN) films is discussed. Designing the precursor structure to provide improved film properties in a plasma-enhanced chemical vapor deposition (PECVD) system is demonstrated. The precursor was optimized for maximizing the density value of the deposited film for a given dielectric constant without compromising the electrical properties. For the deposited SiCN films, the nature of carbon bonding was identified as a key structural element correlating to critical barrier film properties such as leakage and hardness.

Multicolor ${\rm ITO}/{\rm SiO}_{x}/{\rm p}\hbox{-}{\rm Si}/{\rm Al}$ Light Emitting Diodes With Improved Emission Efficiency by Small Si Quantum Dots

In this paper, multicolor ITO/SiO <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> /p-Si/Al light emitting diodes (LEDs) made by Si quantum dot (Si-QD) embedded Si-rich SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> grown by detuning the radio frequency (RF) plasma power under the plasma-enhanced chemical vapor deposition system are presented. With the Si-QD size shrinkage obtained by increasing the RF plasma powers from 30 to 70 W, the turn-on voltage of red, green, and blue ITO/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /p-Si/Al LEDs is found to increase from 70 to 99 V, with the maximum electroluminescent power increasing from 9 to 423 nW.

Duty ratio impact on SiN films deposited in SiH 4-NH 3 plasma at room temperature

Silicon nitride (SiN) films were deposited by using pulsed plasma-enhanced chemical vapor deposition system. The experiments were conducted from SiH 4 and NH 3 plasma at room temperature. The duty ratio was varied in the range 40–90%. Duty ratio-induced ion energy diagnostics was conducted using a non-invasive ion energy analyzer. Ion energy variables collected include a high ion energy ( E h ), a low ion energy ( E l ), a high energy flux ( N h ), a low ion energy flux ( N l ). Their various ratios were calculated to examine relationships between ion energy and film properties, including deposition rate, refractive index, and surface roughness. It is noticeable that high deposition rate of more than 1150 Å/min could be achieved at 60%. The deposition rate and surface roughness highly correlated with N h . From the variation of refractive index, deposition mechanisms were inferred. The deposition rate, refractive index, and surface roughness were varied in a range of 1003–1148 Å/min, 1.64–1.96, and 1.37–3.07 nm, respectively.

Neural network modeling of inter-characteristics of silicon nitride film deposited by using a plasma-enhanced chemical vapor deposition

Neural network have been widely used to model a relationship between process parameters (or in situ diagnostic variables) and film qualities. A new neural network model relating inter-relationship between the film qualities, not the process parameters is constructed by using a generalized regression neural network and a genetic algorithm. This approach is applied to the lifetime of silicon nitride films deposited by using a plasma-enhanced chemical vapor deposition system. The lifetime is an important quality that determines the efficiency of solar cells. The other film qualities examined are a deposition rate, a refractive index, and a charge density. For a systematic modeling, the deposition process was modeled by using a statistical experiment. Compared to conventional and statistical regression models, the optimized GRNN model demonstrated an improvement of 73% and 81%, respectively. The model predicted important and useful clues to optimizing the lifetime. It is noticeable that higher lifetime was achieved at lower deposition rate. This was also noted as the charge density was decreased. The refractive index played a critical role in improving the lifetime.

Raman characterization of the structural evolution in amorphous and partially nanocrystalline hydrogenated silicon thin films prepared by PECVD

AbstractHydrogenated silicon (Si:H) thin films were obtained by plasma‐enhanced chemical vapor deposition (PECVD). Raman spectroscopy was used to investigate the structural evolution in phosphor‐doped n‐type amorphous hydrogenated silicon thin films, which were prepared under different substrate temperatures and gas pressures. Meanwhile, the effect of nitrogen doping on the structure of P‐doped thin films was also investigated by Raman spectroscopy. Moreover, the transition from the amorphous state to the nanocrystalline state of undoped Si:H films deposited through low argon dilution was studied by Raman spectroscopy, X‐ray diffraction, and transmission electron microscopy. The results show that Raman spectroscopy can sensitively detect the structural evolution in hydrogenated silicon thin films deposited under different conditions in a PECVD system. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Effect of annealing treatments on photoluminescence and charge storage mechanism in silicon-rich SiN x :H films

In this study, a wide range of a-SiNx:H films with an excess of silicon (20 to 50%) were prepared with an electron-cyclotron resonance plasma-enhanced chemical vapor deposition system under the flows of NH3 and SiH4. The silicon-rich a-SiNx:H films (SRSN) were sandwiched between a bottom thermal SiO2 and a top Si3N4 layer, and subsequently annealed within the temperature range of 500-1100°C in N2 to study the effect of annealing temperature on light-emitting and charge storage properties. A strong visible photoluminescence (PL) at room temperature has been observed for the as-deposited SRSN films as well as for films annealed up to 1100°C. The possible origins of the PL are briefly discussed. The authors have succeeded in the formation of amorphous Si quantum dots with an average size of about 3 to 3.6 nm by varying excess amount of Si and annealing temperature. Electrical properties have been investigated on Al/Si3N4/SRSN/SiO2/Si structures by capacitance-voltage and conductance-voltage analysis techniques. A significant memory window of 4.45 V was obtained at a low operating voltage of ± 8 V for the sample containing 25% excess silicon and annealed at 1000°C, indicating its utility in low-power memory devices.

Control of Seed Detachment in Au-Assisted GaN Nanowire Growths

The detachment and migration of Au catalyst seeds in the Au-assisted growth of GaN nanowires are observed to be controlled by the partial pressure of gallium and nitrogen radicals in the plasma-enhanced chemical vapor deposition system. The migration rate of Au catalyst increases with increasing the gallium vapor pressure during the growth. With the increasing gallium partial pressure, the compositions of gallium in the Au−Ga seeds of nanowires increase, which dramatically enhances the instability and the detaching of Au seeds during the growth. Besides, the gallium atoms adsorbed on the nanowire surface may act as a surfactant to facilitate the Au migration. Therefore, the increase of gallium partial pressure increases the amount of gallium atoms adsorbed on the nanowire surface and further enhances the rate of Au migration along the nanowire. On the other hand, with the increase of gas phase nitrogen radical concentration, an increasing amount of nitrogen atoms can be adsorbed on the nanowire surface to hinder Au migration along the nanowire. In addition to the vapor−liquid−solid (VLS) growth process observed, the growth of GaN nanowires via the vapor−solid−solid (VSS) process is also observed. In VSS growth, the detachment of solid Au seeds was inhibited dramatically.

The Simulation of Polycrystalline Silicon Thin Film Deposition in PECVD System

Taking Silicon tetrachloride (SiCl4) and hydrogen (H2) as the reaction gas, by the method of plasma-enhanced chemical vapor deposition (PECVD), this paper simulates the deposition process of polycrystalline silicon thin film on the glass substrates in the software FLUENT. Three dimensional physical model and mathematics model of the simulated area are established. The reaction mechanism including main reaction equation and several side equations is given during the simulation process. The simulation results predict the velocity field, temperature distribution, and concentration profiles in the PECVD reactor. The simulation results show that the deposition rate of silicon distribution is even along the circumference direction, and gradually reduced along the radius direction. The deposition rate is about 0.005kg/(m2•s) at the center. The simulated result is basically consistent with the practical one. It means that numerical simulation method to predict deposition process is feasible and the results are reliable in PECVD system.

Controlled Synthesis of Carbon Nanowalls for Carbon Channel Engineering

This study investigates the growth mechanisms of carbon nanowalls (CNWs), which are two-dimensional carbon structures that consist of stacked graphene sheets and that stand vertically on substrates. Factors that determine their morphological and electrical properties were studied using two plasma-enhanced chemical vapor deposition (PECVD) systems that permit the densities and energies of radicals and ions to be precisely controlled. For CNW growth using a C2F6/H2 plasma, the CNW growth rate decreased when the total pressure was increased from 13.3 to 80 Pa during growth. Raman spectroscopy and scanning electron microscopy revealed that the CNW crystallinity increases and the CNW density decreases with increasing total pressure. This is attributed to an increasing amount of H radicals in the growth ambient with increasing total pressure. During the initial stages of CNW growth using a multibeam PECVD system with CFx, hydrogen radicals, and Ar ions, CNWs were formed only for Ar+-ion fluxes of 3.3 to 3.8 A/cm2 and energies of 200 to 250 eV. Although attachment of CFx radicals and CNW growth require ion bombardment, if the flux or energy of ion bombardment is too high CNW growth will be inhibited due to etching and excessive carbon deposition. Semiconducting CNWs with n-type characteristics can be formed by adding N2 gas to the C2F6/H2 plasma. Furthermore, carrier concentrations of n-type CNWs can be controlled by nitrogen doping.

Improved properties of Ti-doped ZnO thin films by hydrogen plasma treatment

This work investigates the effects of substrate temperature ( T S ) and hydrogen plasma post-treatment on the properties of TZO thin films prepared by radio frequency magnetron sputter. All films had a (002) preferential orientation along the c axis at 2θ ~ 34°. As T S increased from room temperature to 300 °C, the structural, electrical, and optical characteristics of the TZO films were enhanced. The hydrogen plasma was performed by a plasma-enhanced chemical vapor deposition system at 300 °C. The film resistivity decreased markedly by 60% to 1.20 × 10 − 3 Ω cm after a 90-min treatment in comparison with that of the as-deposited film. The improved characteristics of the plasma-treated TZO films are attributed to the formation of shallow donors and the desorption of oxygen species at grain boundaries during hydrogen plasma treatment.