Inductively Coupled Plasma Chemical Vapor Deposition Research Articles

Silicon Nitride Deep-Ultraviolet Photoconductive Detector

In this letter, amorphous silicon nitride (Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) film grown by inductively coupled plasma chemical vapor deposition (ICPCVD) method is used as the photosensitive layer of deep ultraviolet (DUV) detection, whose thickness and roughness are 200 nm and 0.92 nm, respectively. The transverse symmetrical photoconductive detector with interdigital electrodes spacing of 4 μm is fabricated by photolithography, exhibiting ultrahigh photo-to-dark current ratio (PDCR) more than 105, fast fall speed of 127 ms and also a satisfying responsivity of 1.09 mA/W. This work lays a foundation for further researches on Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> in photonics and electronics.

Photoluminescence from carbon structures grown by inductively coupled plasma chemical vapor deposition

Carbon micro/nanostructures were grown by inductively coupled plasma chemical vapor deposition (ICP-CVD) at low pressure into a tubular reactor under pure methane and using substrates of SAE 304 stainless steel. The samples show diverse structures and properties depending on the position inside the quartz tube, due to the different temperatures and environmental conditions. In this experiment, the authors have obtained structures with different scales (micro and nano), depending on the growing temperature and the position inside the reactor. Carbon microstructures were obtained on the extreme parts of the tubular reactor at low temperatures. In contrast, carbon nanostructures appeared after the plasma resonator at temperatures higher than 700 °C. X-ray photoelectron spectroscopy and Fourier transform infrared spectrometry evidenced functional groups with hydrogen and oxygen atoms except for nanostructures at 750 °C showing vertical carbon nanowalls with more than ten crystalline layers, such as it was verified by field emission SEM, TEM, and Raman shift spectroscopy. An intense photoluminescence in the visible range was revealed from the samples excited by laser (325 nm), except the nanowall samples, which exhibited a poor photoluminescence. The purpose of this work is to study the photoluminescence of carbon structures produced by ICP-CVD and to evidence the role of hydrogen and oxygen functional groups with hydrogen and oxygen atoms. The understanding of these processes provides additional criteria for designing new materials based on carbon, which is environmentally friendly, for application to luminescent devices.

Novel high-k gate dielectric properties of ultrathin hydrocarbon films for next-generation metal-insulator-semiconductor devices

New high-k gate dielectrics are highly necessary in facilitating the continuous down-scaling of metal–oxide–semiconductor devices to the sub-10 nm range. This study presents ultrathin organic hydrocarbon (HC) films as a novel high-k gate insulator for metal–insulator–semiconductor (MIS) devices. During inductively-coupled plasma chemical vapor deposition with CH4 and H2 gases, the growth temperature greatly affects the structure of the carbon layers and consequently their dielectric characteristics. Specifically, sp2-rich dielectric HC layers are formed below 600 °C, whereas highly-ordered sp2-hybridized graphene is formed at 950 °C. The k value of the resulting HC films increases up to a maximum value of 90 at 350 °C. Moreover, the MIS devices exhibit excellent gate-insulating properties, including almost no hysteresis in the capacitance–voltage curve, low leakage current, and high dielectric strength, which surpass those of existing high-k gate oxides. These results reveal that the organic HC films are a promising next-generation high-k gate dielectric material for sub-10 nm node Si and organic semiconductor technologies.

Low Reflection and Low Surface Recombination Rate Nano-Needle Texture Formed by Two-Step Etching for Solar Cells.

In this study, needle-like and pyramidal hybrid black silicon structures were prepared by performing metal-assisted chemical etching (MACE) on alkaline-etched silicon wafers. Effects of the MACE time on properties of the black silicon wafers were investigated. The experimental results showed that a minimal reflectance of 4.6% can be achieved at the MACE time of 9 min. The height of the nanostructures is below 500 nm, unlike the height of micrometers needed to reach the same level of reflectance for the black silicon on planar wafers. A stacked layer of silicon nitride (SiNx) grown by inductively-coupled plasma chemical vapor deposition (ICPCVD) and aluminum oxide (Al2O3) by spatial atomic layer deposition was deposited on the black silicon wafers for passivation and antireflection. The 3 min MACE etched black silicon wafer with a nanostructure height of less than 300 nm passivated by the SiNx/Al2O3 layer showed a low surface recombination rate of 43.6 cm/s. Further optimizing the thickness of ICPCVD-SiNx layer led to a reflectance of 1.4%. The hybrid black silicon with a small nanostructure size, low reflectance, and low surface recombination rate demonstrates great potential for applications in optoelectronic devices.

Numerical Simulation of Crystalline Silicon Heterojunction Solar Cells with Different p-Type a-SiOx Window Layer

In this study, p-type amorphous silicon oxide (a-SiOx) films are deposited using a radio-frequency inductively-coupled plasma chemical vapor deposition system. Effects of the CO2 gas flow rate on film properties and crystalline silicon heterojunction (HJ) solar cell performance are investigated. The experimental results show that the band gap of the a-SiOx film can reach 2.1 eV at CO2 flow rate of 10 standard cubic centimeters per minute (sccm), but the conductivity of the film deteriorates. In the device simulation, the transparent conducting oxide and contact resistance are not taken into account. The electrodes are assumed to be perfectly conductive and transparent. The simulation result shows that there is a tradeoff between the increase in the band gap and the reduction in conductivity at increasing CO2 flow rate, and the balance occurs at the flow rate of six sccm, corresponding to a band gap of 1.95 eV, an oxygen content of 34%, and a conductivity of 3.3 S/cm. The best simulated conversion efficiency is 25.58%, with an open-circuit voltage of 741 mV, a short-circuit current density of 42.3 mA/cm2, and a fill factor of 0.816%.

Synthesis of nanostructured based carbon nanowalls at low temperature using inductively coupled plasma chemical vapor deposition (ICP-CVD)

Synthesis of carbon nanowalls using inductively coupled plasma chemical vapor deposition is investigated in this article. This paper reports the growth of nanowalls at low temperature with effective results. Xylene was tested in combination with Ni film as catalyst to grow nanowalls. Various substrates, parameters and conditions were used for the growth purposes. Results obtained with xylene were promising for the growth of nanostructured based carbon nanowalls in the investigated parameter range. Results has been confirmed using scanning electron microscope, optical emission spectroscopy and Raman spectroscopy.

Surface passivation of crystalline silicon by intrinsic a-Si:H films deposited in remote low frequency inductively coupled plasma

Intrinsic hydrogenated amorphous silicon (a-Si:H) thin films was prepared in remote low-frequency inductively coupled plasma chemical vapour deposition (ICP-CVD) system for surface passivation on single crystalline silicon (c-Si). The influences of deposition temperature and precursor gas flow rate on the physical properties of a-Si:H thin films and the passivation effect of a-Si:H/c-Si interfaces were investigated. High quality a-Si:H thin films with less vacancies and defects were fabricated in remote ICP-CVD by eliminating the direct impacting of energetic plasma radicals on deposition surface. The passivation performance on c-Si were also improved in remote ICP-CVD, a minority carrier lifetime ~2.32 × 10−3 s was achieved by fabricating 10 nm a-Si:H passivation layer on c-Si substrate.

Mechanism of dense silicon dioxide films deposited under 100 °C via inductively coupled plasma chemical vapor deposition

High density of the inductively coupled plasma chemical vapor deposition (ICPCVD) enables growth of films on soft substrate such as polyethylene terephthalate (PET) that otherwise curls at temperatures higher than 100 °C. In this study, dense silicon oxide (SiOx) films are prepared on PET by ICPCVD. Intrusive optical emission spectroscopy is employed to monitor distribution of the plasma radicals during the deposition process. The study discovers a direct relationship between the dense structure of the deposited film and the CH/(CH + OH) plasma radical intensity ratio. The deposition plasma with the lowest CH radical ratio results in the SiOx film with the least CHx incorporation and densest film structure. The film exhibits the smallest etched area in hydrochloric acid etching tests and the minimal water-vapor transmission rate of about 1.5 × 10−1 g/m2/day.

Effects of radio frequency power and gas ratio on barrier properties of SiOxNy films deposited by inductively coupled plasma chemical vapor deposition

SiOxNy barrier films were deposited at low temperature of ~ 23 °C using inductively coupled plasma chemical vapor deposition (ICP-CVD). When radio frequency power increased at constant ratios of Ar/SiH4 and O2/(O2 + N2), respectively, of 4.5 and 0.1, the aggregation tendency of nanoparticles slightly decreased, whereas when the ratio of Ar/SiH4 was changed from 4.5 to 41, almost spherical nanoparticles, each of which was isolated without aggregation, were observed. Such a near spherical nanoparticle without aggregation produced highly dense films with enhanced barrier property. However, heavily aggregated nanoparticles produced very porous films with deteriorated barrier property. In other words, the film density and barrier property depended significantly on whether nanoparticles were isolated or aggregated. To investigate the formation mechanism of dense SiOxNy barrier film, a transmission electron microscope grid membrane was exposed for 5 s to capture nanoparticles generated in the gas phase using a shutter above the grid membrane during ICP-CVD and the grid membrane was observed by scanning transmission electron microscope. The formation mechanism of the barrier film could be best explained by non-classical crystallization of CVD films, where nanoparticles formed in the gas phase contribute to the film formation.

Interview

Jin Cho from the University Of Glasgow, UK, talks to Electronics Letters about his paper ‘The Impact of Stress in ICP-CVD SiNx Passivation Films on the Leakage Current in AlGaN/GaN HEMTs’, page 947. Jin Cho My current research interest includes development of high power, high breakdown voltage, and low switching energy loss in metal oxide semiconductor high electron mobility transistors (MOS-HEMT) using gallium nitride (GaN) on silicon (Si). Compared to Si power devices, wide band gap power devices such as GaN transistors offer great performance improvements due to their significantly better material properties. GaN has a higher bandgap, breakdown field, and electron mobility compared to Si, which leads to greater performance in power electronics. Since improving the performance of power converters will lead to saving energy consumption of electrical machines in factories, I am particularly interested in GaN power transistor design, fabrication, and characterisation for power converter applications Improvement of the on- and off-switching speed and minimised switching energy loss are essential parameters for all of power converter applications. To do this, we need to minimise the two main leakage currents in a GaN transistor, namely the off-state drain-to-source, and the gate leakage currents. These leakage currents are affected significantly by the different types of passivation material and/or deposition technique. Passivation is a vital fabrication step for all of multi-layer thin film devices. Silicon nitride (SiNx) has been broadly used as a passivation film material and shown to improve device performance. However, several papers have been reported leakage currents of GaN transistors also being increased by SiNx passivation film. To address this problem, we investigated the characteristics of SiNx passivation films and their impact on leakage currents in GaN transistors. To mitigate leakage currents, several methods have been reported in the literature such as aluminium oxide (Al2O3) passivation film deposited by atomic layer deposition, wet chemical, or plasma surface treatment before passivation and rapid thermal annealing after passivation. In this Letter, we proposed to reduce leakage currents by exploiting the physical stress in the SiNx passivation scheme. Most thin films tend to be in either tensile or compressive stress. Indeed, a few papers have been investigating stress of SiNx in the passiviation film of GaN HEMT. To date, all reports on the impact of stressed SiNx films have been restricted to passivation layers deposited by plasma enhanced chemical vapour deposition (PECVD) techniques with a maximum compressive stress of 150 MPa. Up to this level of stress, no change or improvement in the transistor leakage currents was seen. In our work, we realised leakage current mitigation under both tensile and compressive stress in the range of −1622 to +440 MPa for room temperature deposited inductively coupled plasma chemical vapour deposition (ICPCVD) SiNx passivation films. A significant reduction in off-state drain-to-source and gate leakage currents was observed for the optimally stressed films. The key parameter to reduced leakage currents is to realise the high stress level of SiNx deposition. Properties of SiNx film show that the leakage current can be changed by variation of the stress level. Due to two kinds of plasma power, ICP-CVD can make very high tensile/compressive type of SiNx. Off-state drain-to-source and gate leakage current was reduced by up to four orders of magnitude when compared to unpassivated devices. However, high compressive stressed SiNx films were shown to be randomly cracked and had delamination issues across the surface. It was discovered that this situation could be overcome by first depositing SiNx films using low or medium stressed process, followed by the higher stress films. In both the short and longer terms, high stressed SiNx film can be directly used as passivation for all of GaN based power or radio frequency (RF) HEMTs to mitigate their unwanted leakage currents. Further optimisation work for this approach would be useful. We are using the developed passivation technique in the realisation of new GaN power device that we are developing. The work includes assessing the switching characteristics of these devices. I have studied GaN based transistors since 2010. I see the key challenges for this technology being to increase cost effectiveness and reliability. In my opinion, over the next ten years, the future challenges will be how to improve device performances and reliability under extreme environments.

Ka band High RF performance AlGaN/GaN HEMTs

To realize high RF performance AlGaN/GaN high electron mobility transistor (HEMT), two SiNx passivation layers were respectively grown on the surface of AlGaN/GaN epi wafer by inductively coupled-plasma chemical vapor deposition (ICP-CVD) and plasma enhanced chemical vapor deposition (PECVD). The two-stage passivation can effectively suppress the current collapse and decrease the parasitic parameters. To verify the performance improvement, a 6 × 50 μm GaN HEMT device was fabricated and measured. The device shows a maximum drain current of about 1067 mA/mm and a maximum transconductance of about 433 mS/mm, the cut-off frequency (fT) of 45.4 GHz at a gate bias of -1.5 V and a drain bias of 20 V. The device shows a power density of 3.7 W/mm, a power-added efficiency (PAE) of 46.5% and power gain of 8.5 dB by load-pull measurement. In addition, a 34-36 GHz GaN monolithic microwave integrated circuit (MMIC) was fabricated, which exhibits an output power of about 41.5 dBm, a PAE of 20% and a gain of 15.5 dB.

Inductively and capacitively coupled plasmas at interface: A comparative study towards highly efficient amorphous-crystalline Si solar cells

A comparative study on the application of two quite different plasma-based techniques to the preparation of amorphous/crystalline silicon (a-Si:H/c-Si) interfaces for solar cells is presented. The interfaces were fabricated and processed by hydrogen plasma treatment using the conventional plasma-enhanced chemical vacuum deposition (PECVD) and inductively coupled plasma chemical vapour deposition (ICP-CVD) methods The influence of processing temperature, radio-frequency power, treatment duration and other parameters on interface properties and degree of surface passivation were studied. It was found that passivation could be improved by post-deposition treatment using both ICP-CVD and PECVD, but PECVD treatment is more efficient for the improvement on passivation quality, whereas the minority carrier lifetime increased from 1.65×10−4 to 2.25×10−4 and 3.35×10−4s after the hydrogen plasma treatment by ICP-CVD and PECVD, respectively. In addition to the improvement of carrier lifetimes at low temperatures, low RF powers and short processing times, both techniques are efficient in band gap adjustment at sophisticated interfaces.

Synthesis of anode active material particles for lithium-ion batteries by surface modification via chemical vapor deposition and their electrochemical characteristics

The high capacity and optimal cycle characteristics of silicon render it essential in lithium-ion batteries. We have attempted to realize a composite material by coating individual silicon (Si) particles of μm-order diameter with a silicon oxide film to serve as an active material in the anode of a lithium-ion battery and thus improve its charge-discharge characteristics. The particles were coated using an inductively coupled plasma-chemical vapor deposition (ICP-CVD) process that realized a homogeneously coated silicon oxide film on each Si particle. The film was synthesized using 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 oxide deposition by ICP-CVD. The silicon oxide covering the Si particles included both silicon monoxide and suboxide, which served to improve the charge-discharge characteristics. We succeeded in realizing an active material using Si, which is abundant in nature, for the anode of a lithium-ion battery with highly charged, improved cycle properties.

Understanding the Growth Kinetics of Graphene on Cu and Fe2O3 Using Inductively-Coupled Plasma Chemical Vapor Deposition

Understanding the Growth Kinetics of Graphene on Cu and Fe₂O₃ Using Inductively-Coupled Plasma Chemical Vapor Deposition

Optimization of residual stress of SiO2/organic silicon stacked layer prepared using inductively coupled plasma deposition

Silicon dioxide (SiO2) has great potential to be used for thin-film encapsulation for flexible electronic devices, but it easily peels off with a large thickness to fail encapsulation. In this study, organic silicon films with high transmittance and tensile stress are prepared and inserted into SiO2 and polyethylene terephthalate substrate to reduce residual stress. Radiofrequency inductively coupled plasma chemical vapor deposition (ICPCVD) with a gas mixture of argon and trimethylsilane is used for organic silicon film deposition, and the power is varied to investigate its effect on film properties. The plasma emission spectra show that the power of 900W leads to a balance between the increase in precursor radical intensities and reduction in ion bombardment at increasing power. The resultant film has the highest refractive index value, the largest ratio of SiCSi to SiCHx terminate bonds and the smoothest surface morphology. The residual stress of SiO2 can be tremendously reduced from −360 to −31.6MPa with organic silicon layer beneath. Furthermore, the eight-pair SiO2/organic silicon stacked encapsulation barrier demonstrates a transmittance of 85.4%, water-vapor transmission rate of 8.3×10−10g/cm2/day, and a residual stress of −102MPa.

Effect of substrate bias on deposition behaviour of charged silicon nanoparticles in ICP-CVD process

The effect of a substrate bias on the deposition behaviour of crystalline silicon films during inductively coupled plasma chemical vapour deposition (ICP-CVD) was analysed by consideration of non-classical crystallization, in which the building block is a nanoparticle rather than an individual atom or molecule. The coexistence of positively and negatively charged nanoparticles in the plasma and their role in Si film deposition are confirmed by applying bias voltages to the substrate, which is sufficiently small as not to affect the plasma potential. The sizes of positively and negatively charged nanoparticles captured on a carbon membrane and imaged using TEM are, respectively, 2.7–5.5 nm and 6–13 nm. The film deposited by positively charged nanoparticles has a typical columnar structure. In contrast, the film deposited by negatively charged nanoparticles has a structure like a powdery compact with the deposition rate about three times higher than that for positively charged nanoparticles. All the films exhibit crystallinity even though the substrate is at room temperature, which is attributed to the deposition of crystalline nanoparticles formed in the plasma. The film deposited by negatively charged nanoparticles has the highest crystalline fraction of 0.84.

Low-Temperature ICP-CVD SiN&lt;italic&gt;x&lt;/italic&gt;as Gate Dielectric for GaN-Based MIS-HEMTs

SiN x deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD) technique at low temperature (70 °C) was investigated as gate dielectric for AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs). Besides significant reduction in gate leakage current, the MIS-HEMTs showed improvement in drain current characteristics, 2DEG channel mobility, $I_{\mathrm{\scriptscriptstyle ON}}/I_{\mathrm{\scriptscriptstyle OFF}}$ ratio, ON-resistance, and three terminal breakdown voltage as compared with reference HEMTs. Very small capacitance–voltage hysteresis (~68 mV) was observed for a gate swing of −10 to +5 V. The effect of SiN x thickness ( $t_{\mathrm {SiN}x}$ ) on the characteristics of MIS-HEMTs was studied. The performance of fabricated MIS-HEMTs was found to be stable for a wide range of temperature.

Amorphous indium–gallium–zinc–oxide thin-film transistors using organic–inorganic hybrid films deposited by low-temperature plasma-enhanced chemical vapor deposition for all dielectric layers

We investigated the deposition of high-performance organic–inorganic hybrid dielectric films by low-temperature (close to room temperature) inductively coupled plasma chemical vapor deposition (ICP-CVD) with hexamethyldisiloxane (HMDSO)/O2 precursor gas. The hybrid films exhibited low leakage currents and high breakdown fields, suitable for thin-film transistor (TFT) applications. They were successfully integrated into the gate insulator, the etch-stop layer, and the passivation layer for bottom-gate staggered amorphous In–Ga–Zn–O (a-IGZO) TFTs having the etch-stop configuration. With the double-active-layer configuration having a buffer a-IGZO back-channel layer grown in oxygen-rich atmosphere for better immunity against plasma damage, the etch-stop-type bottom-gate staggered a-IGZO TFTs with good TFT characteristics were successfully demonstrated. The TFTs showed good field-effect mobility (μFE), threshold voltage (Vth), subthreshold swing (SS), and on/off ratio (Ion/off) of 7.5 cm2 V−1 s−1, 2.38 V, 0.38 V/decade, and 2.2 × 108, respectively, manifesting their usefulness for a-IGZO TFTs.

Low temperature growth of graphene using inductively-coupled plasma chemical vapor deposition

Abstract This paper investigates the effect of processing parameters on the growth of graphene at a temperature of 300 °C using an inductively-coupled plasma chemical vapor deposition system. Graphene films were grown on Cu films under CH4/H2/Ar plasma and then subsequently transferred to different substrates. The effects of the plasma power, deposition time and CH4 flow rate on the characteristics of the graphene films were systematically investigated. The results show that AB-stacked bilayer graphene films can be grown at low flow rates of CH4 and low plasma powers for depositions as short as 10 s. The bilayer graphene films exhibited surface enhanced Raman scattering effects and enabled detection of a reporter molecule presenting an example application. Low temperature growth at short processing times may enable realization of the potential uses of graphene in a wide range of applications at practical costs with relaxed constraints on the materials and processes associated with high temperatures.

High efficiency light-induced dielectrophoresis biochip prepared using CVD techniques.

This article describes a high-efficiency light-induced dielectrophoresis biochip containing a thin film prepared through inductively coupled plasma chemical vapor deposition (ICPCVD). The biochip comprises two ITO glass substrates and a photoconductive amorphous silicon thin film. The biochip can effectively sort particular particles (or cells) by projecting visible light onto the surface of the silicon thin film. The sorting efficiency of biochips is highly associated with the quality of the deposited amorphous silicon thin films; therefore, the choice of deposition technique is extremely critical. However, no study has examined this problem. Hence, the current study thoroughly compared the efficiency of the biochip when films produced through plasma-enhanced chemical vapor deposition and ICPCVD are used.