Silicon Oxynitride Research Articles

Alternating silicon oxy-nitride and silicon oxide stripe formation by nitric oxide (NO+) ion implantation

We report nitric oxide ion (NO+) beam induced nanoscale pattern formation on Si (100) surface. The patterns are found to be structurally as well as chemically periodic. A highly reactive 14 keV NO+ beam is developed in an Electron Cyclotron Resonance ion beam system and implanted on Si (100) surface at oblique angles to form a periodic nano-ripple pattern with specific silicon oxide and silicon oxy-nitride enriched sectors with different dielectric constants. Well-defined ripple patterns start to form at comparatively lower ion fluences due to an additional instability generation by the chemical reaction of NO+ ions with silicon. The chemical shift of the Si 2p peak in the x-ray photoelectron spectroscopy study of an ion irradiated sample confirms the formation of silicon oxide and silicon oxy-nitride, whereas the local chemical nature of the ion induced ripple patterns, probed by electron energy loss spectroscopy, approves spatially resolved silicon oxide and silicon oxy-nitride stripe pattern formation. The ion modified layer thickness measured by cross-sectional transmission electron microscopy has an excellent agreement with Monte Carlo simulations. The optical sensitivity of an NO+ bombarded chemically patterned Si surface is also studied by UV–Visible spectroscopy. Formation mechanisms and potential applications of such nano-scale spatially graded materials are discussed.

Micro‐patterned Bioactive Amorphous Silicon Oxynitride Enhances Adhesion, Growth, and Myotubes and Axon Alignment in Muscle and Nerve Cells

IntroductionTraumatic injuries lead to volumetric muscle loss (VML) and nerve damage that cause chronic functional deficits. Due to the inability of mammalian skeletal muscle to regenerate the damaged tissue in VML injuries, muscle flap procedures have been used. Functional muscle transfer, including vasculature and innervation, has been shown to improve strength to an injured muscle. However, most muscle flap procedures are not intended to restore muscle function except in limited circumstances. Thus, these procedures have not adequately addressed this issue and novel engineered materials that regenerate the damaged tissue and restore the functionality is crucially needed. Here, we introduce novel bioactive amorphous silica‐base biomaterials that accelerate muscle, nerve, and vascular healing for fully functional tissue regeneration.Materials and MethodsMicro‐patterned scaffolds were designed and developed on Si‐wafer using photolithography, then 200 nm layer of SiONx was deposited by Plasma Enhanced Chemical Vapor Deposition technique. C2C12 mouse myoblast and NG108‐15 neuroblastoma x rat glioma hybrid cell lines were used for in‐vitro studies. In‐vitro studies using different ionic silicon concentration (0.1, 0.5, and 1.0 mM) were performed to determine the optimal concentration for muscle and nerve cells. MTS assay and fluorescence microscopy were used to study the cell viability, growth, and differentiation. Also, qRT‐PCR was used to investigate the targeted gene expression.ResultsIn‐vitro studies revealed that 0.1 mM of Si4+ significantly enhance the C2C12 cell growth, fusion index (1.5 fold), and the area covered by myotubes (*** p<0.001) compared to the control (Fig. 1). Also, 0.1 mM of Si4+ significantly increase the NG108‐15 neural cell viability after 12 hours in growth media. qRT‐PCR data revealed that 0.1 mM of Si4+ increases MyoD gene expression 3‐folds compared to the control by day 1, and MyoG expression 2‐folds by day 5. Also, 0.5 mM of Si4+ significantly increases the GAP43 gene expression 3‐folds by day 1 of neural cell culture. Intriguingly, 0.5 mM of Si4+ significantly increase Neurturin (Myokine) protein concentration at day 3 of C2C12 cell culture. Most intriguingly, the formed myotubes and axons were perfectly aligned (Fig. 2) on the surface of micro‐patterned SiONx scaffolds (Without laminin coating).ConclusionThis study confirms that 0.1 mM of Si4+ is the optimal concentration for muscle and nerve cells that enhance the cell differentiation and increase the myogenic/neurogenic gene expression as well as myogenic/neurogenic markers. Surface pattern successfully support axons and myotubes alignment on the SiONx surface.Support or Funding InformationNational Institutes of Health (Grant No. 1R56DE027964‐01A1‐01)University of Texas STARS award ProgramSi‐ions (0.1 mM) enhance Fusion index, total number of cells, and area covered by myotubes in C2C12 cells after 4 days of differentiation.Figure 1aligned axons and myotubes on the patterned SiONx. A) DAPI and MHC Stained myotubes, b) Refractive microscopy image of the aligned myotubes, C) Neural network formation on the smooth surface of SiON, and D) axon alignment on the patterned SiON.Figure 2

A novel AGNR/h-BN transistor with tunable negative differential resistance

Abstract An important issue in devices with negative differential resistance (NDR) in I–V characteristics is the ability to control device characteristics. In this paper, a novel double-gate AGNR/h-BN FET with a tunable NDR in the I–V characteristic is proposed for the first time. An armchair GNR is used in this device with length of 6.4 nm and width of 2.2 nm. The insulator used in this device is silicon oxynitride due to higher dielectric constant compared with silicon dioxide in order to improve gate control, and more feasibility than high-k materials since it has native silicon oxide. The interesting feature of this device is its ability to tune NDR in the output characteristics. It is observed that positive gate-source voltages reduce the peak to valley current differences and, negative gate-source voltages increase the peak to valley current differences. By tuning the NDR, the biasing condition and even the oscillation condition of the transistor can be tuned when it is used as an oscillator, for example. In addition, the current and power consumption of the device can be controlled.

Enhanced red light emission from dense Si quantum dot-based silicon oxynitride light-emitting diodes with reduced efficiency droop

Strong red light emission from silicon oxynitride-based (SiOxNy-based) light-emitting diodes (LEDs) was investigated. The introduction of dense Si quantum dots (Si QDs) into SiOxNy not only increases carrier injection efficiency but also results in a significant enhancement of more than 300% in the light emission efficiency compared with SiOxNy-based LEDs without Si QDs. Moreover, the efficiency droop phenomenon is remarkably suppressed in the SiOxNy-based LED containing dense Si QDs. Analysis of the dominant recombination process indicates that the improved performance of the SiOxNy-based LEDs results from the increased bimolecular radiative recombination probability.

Characterization of silicon oxynitride films deposited by a high-power impulse magnetron sputtering deposition technique.

In this research, silicon oxynitride films were prepared by high-power impulse magnetron sputtering with 45/955 pulse on/off time. The extinction coefficient was smaller than 1×10-3 from 250 to 700 nm after introducing 2.2 sccm O2 gas at room temperature. A three-layer of AlF3/SiOxNy AR coating was designed and fabricated on double-sided quartz, and a high transmittance of 99.2% was attained at 248 nm. The silicon oxynitride films deposited at 350°C had the better mechanical and optical properties in the visible range. The hardness of all deposited films was greater than 19 GPa, and the greatest hardness could reach to 29.8 GPa. A film structure of six-layer transparent hard coating/glass/four-layer AR coating was designed and deposited. Its average transmittance was 96.0% in the visible range, while its hardness was 21 GPa and its surface roughness was 0.23 nm.

A Novel High-Pressure Tin Oxynitride Sn2 N2 O.

We report the first oxynitride of tin, Sn2N2O (SNO), exhibiting a Rh2S3‐type crystal structure with space group Pbcn. All Sn atoms are in six‐fold coordination, in contrast to Si in silicon oxynitride (Si2N2O) and Ge in the isostructural germanium oxynitride (Ge2N2O), which appear in four‐fold coordination. SNO was synthesized at 20 GPa and 1200–1500 °C in a large volume press. The recovered samples were characterized by synchrotron powder X‐ray diffraction and single‐crystal electron diffraction in the TEM using the automated diffraction tomography (ADT) technique. The isothermal bulk modulus was determined as B o=193(5) GPa by using in‐situ synchrotron X‐ray diffraction in a diamond anvil cell. The structure model is supported by DFT calculations. The enthalpy of formation, the bulk modulus, and the band structure have been calculated.

Improvement of emission and thermal stability induced by selected occupation of Al3+ in Ba3Si6O12N2:Eu2+ phosphors

Oxynitride Ba3Si6O12N2:Eu2+ phosphor can usually exhibit high color purity emission spectrum and outstanding thermal stability because of its rigid structure which can be widely used in WLEDs. With the aim of further optimizing the emission intensity, color purity and thermal stability, Al3+-doped Ba3Si6O12N2:Eu2+ green phosphors were successfully prepared by a high-temperature sintering method in the current work. The crystal structure was clearly investigated by the XRD patterns and Rietveld refinement. The expanding volume and elemental analysis proved that Si4+ ions can be efficiently substituted by Al3+ ions in the Ba3Si6O12N2:Eu2+ phosphor. With increasing doping of Al3+ ions, the full width at half maximum decreased from 66.88 to 65.12 nm with an optimal color purity of 65.95%, and the reason was clearly elucidated by the Gaussian fitting spectrum and decay times. Moreover, the emission intensity of Ba3Si6O12N2:0.1Eu2+, 0.03Al3+ was 120% of the intensity of the Al-free sample, and the internal quantum efficiency could reach 70%. The thermal stability was also remarkably enhanced as Al3+ substituted Si4+ in Ba3Si6O12N2:0.1Eu2+, and Ba3Si6O12N2:0.1Eu2+, 0.03Al3+ exhibited only 8% emission loss at 200 °C compared with that at ambient temperature. The outstanding thermal stability was clearly explained by the thermoluminescence spectra and configurational coordinate diagram. The results indicate that the introduction of Al3+ ions can be a versatile method to improve the optical properties of silicon oxynitride.

Surface plasmon enhanced Organic color image sensor with Ag nanoparticles coated with silicon oxynitride

As organic photodetectors with less than 1 μm pixel size are in demand, a new way of enhancing the sensitivity of the photodetectors is required to compensate for its degradation due to the reduction in pixel size. Here, we used Ag nanoparticles coated with SiOxNy as a light-absorbing layer to realize the scale-down of the pixel size without the loss of sensitivity. The surface plasmon resonance appeared at the interface between Ag nanoparticles and SiOxNy. The plasmon resonance endowed the organic photodetector with boosted photon absorption and external quantum efficiency. As the Ag nanoparticles with SiOxNy are easily deposited on ITO/SiO2, it can be adapted into various organic color image sensors. The plasmon-supported organic photodetector is a promising solution for realizing color image sensors with high resolution below 1 μm.

Optimized optical design of thin-film transistor arrays for high transmittance and excellent chromaticity

Transmittance and chromaticity are essential requirements for optical performance of thin-film transistor (TFT) arrays. However, it is still a challenge to get high transmittance and excellent chromaticity at the same time. In this paper, optimized optical design by using antireflection film theory and optical phase modulation is demonstrated in low temperature poly-silicon (LTPS) TFT arrays. To realize high transmittance, the refractive index difference of adjacent films is modified by using silicon oxynitride (SiOxNy) with adjustable refractive index. To realize excellent chromaticity, the thicknesses of multilayer films are precisely regulated for antireflection of certain wavelength light. The results show that the transmittance and chromaticity have been improved by about 6% and 18‰, respectively, at the same time, which is a big step forward for high optical performance of TFT arrays. The device characteristics of the TFT arrays with the optimal design, such as threshold voltage and electron mobility, are comparable to those of conventional TFT arrays. The optimized optical design results in enhanced power-conversion efficiencies and perfects the multilayer film design on the basic theory, which has great practicability to be applied in TFT arrays.

High temperature oxidation behaviors of SiON coated AISI 441 in Ar + O2, Ar+H2O, and Ar + CO2 atmospheres

Silicon oxynitride (SiON) coated AISI 441 was prepared by pyrolysis of a dip-coated perhydropolysilazane (PHPS) precursor polymer. The high temperature oxidation behaviors of SiON coated AISI 441 substrates were studied in Ar + O2, Ar+H2O, and Ar + CO2 atmospheres at 800 °C for 100 h. The SiON coated AISI substrates showed better performance in all three atmospheres compared to the uncoated AISI 441 substrate. This improvement was attributed to the dense, crack-free SiON coatings, which provided complete separation between oxidizing species and the steel substrate. A thin oxide scale was observed on top of the SiON coating for all the atmospheres, which was attributed to the reactions between the oxidizing species in the atmosphere and the metallic species (Cr, Mn, and Fe) diffused through the SiON coating from the AISI 441 substrate.

Secondary Silicon Carbide Formed in the Interaction of Nanosized Silicon Carbide with Iron Oxide

The characteristics of superfine powder composites formed in the interaction of nanosized silicon carbide with iron oxide in vacuum and argon at 1200 and 1400°C, respectively, are analyzed. Silicon carbide (β-SiC), iron silicide and carbide, silicon oxide, and silicon oxynitride are main components of the powder composites. The lattice parameter of SiC in the powder composites synthesized in the SiC–Fe2O3 system is determined. In the interaction in the SiC–Fe2O3 powder mixture in vacuum, secondary SiC is synthesized with a lattice parameter that corresponds to the standard parameter for cubic β-SiC. The interaction in an argon atmosphere is accompanied by the synthesis of secondary SiC with a decreased lattice parameter. The minimum lattice parameter (0.4336 nm) is 0.6% smaller than the standard parameter for cubic β-SiC. The morphology of the powder composite synthesized in the SiC–Fe2O3 system is studied. The average particle size of the powder composite decreases with increasing weight content of secondary SiC.

Investigation on the luminescent stability in amorphous silicon oxynitride systems

Light induced degradation is a common phenomenon in the photoluminescence (PL) properties of silicon (Si) based light emitting materials. Based on our previous research of highly efficient luminescent amorphous silicon oxynitride (a-SiNxOy) systems, in this work, we intensively investigated the light induced degradation properties of a-SiNxOy, and then further significantly improved the related PL stability. It was notable that the a-SiNxOy films exhibit a light induced time evolutionary metastable PL and have self-recovery properties when exposed in the air after a period. With the purpose of eliminating the light induced degradation and the meta-stable PL in a-SiNxOy films, we employed thermal annealing combined with pulsed laser annealing processes, which makes the film density improved and weak bond angle eliminated, thus obtaining the high stable luminescent a-SiNxOy films in visible range.

Alternate lanthanum oxide/silicon oxynitride-based gate stack performance enhancement due to ultrathin oxynitride interfacial layer for CMOS applications

Metal–insulator–semiconductor (MIS)-based Pt/La2O3/SiOXNY/p-Si/Pt structures are fabricated using ultrathin silicon oxynitride (SiOXNY ~ 4 nm) interfacial layer underneath of lanthanum (III) oxide (La2O3 ~ 7.8 nm) with Pt as gate electrode for CMOS applications. Capacitance–voltage (C–V) characteristics of Pt/La2O3/SiOXNY/p-Si/Pt at 500 kHz showed a positive gate bias threshold voltage (Vth) shift of ~ 0.43 V (~ 43.8%) and flat-band (Vfb) shift of ~ 1.24 V (~ 42.3%) as compared to Pt/La2O3/p-Si/Pt MIS structures, attributing to the reduction in effective positive oxide charges at La2O3/SiOXNY/Si gate stack. Likewise, conductance–voltage (G–V) characteristics show ~ 0.56 (~ 44.4%) reduction in FWHM for Pt/La2O3/SiOXNY/p-Si/Pt as compared to Pt/La2O3/p-Si/Pt MIS structures revealing the reduction in interface states at La2O3/SiOXNY/Si interface. There is a considerable reduction of effective oxide charge concentration (Neff) ~ 3.99 × 1010 cm−2 by (~ 15.2%) and ~ 56.8% lower gate leakage current density ~ 4.47 × 10−7 A/cm2 (|J|–V) at − 1 V for SiOXNY based MIS structures w.r.t its counterpart. Capacitance–time (C–t) characteristics, constant voltage stress (CVS) and temperature measurements for C–V and |J|–V demonstrate the considerable retention ~ 12 years, electrical improvement and reliability of MIS structures. The depth profile analysis X-ray photoelectron spectroscopy (XPS) for SiOXNY/Si gate stack clearly reveals that less nitrogen concentration in bulk than SiOXNY/Si interface. Atomic force microscopy (AFM) micrographs of La2O3/Si and SiOXNY/Si showed the significantly lesser r.m.s roughness of ~ 1.11 ± 0.39 nm and ~ 0.97 ± 0.11 nm, respectively. Thus, the ultrathin SiOXNY interfacial layer underneath of La2O3 demonstrates a significantly improved electrical performance and prelude the gate stack strong potential for reliable CMOS logic devices and integrated circuits.

Nitriding process for next-generation semiconductor devices by VHF (162 MHz) multi-tile push-pull plasma source

For the low power and high-performance semiconductor devices, a silicon oxynitride (SiOxNy) layer is required as the gate sidewall spacer material by replacing oxygen of the silicon oxide (SiO2) sidewall layer with nitrogen through a plasma nitriding process. In this study, as a plasma nitriding process, instead of conventional radio frequency plasma nitriding utilizing high frequency (HF; 13.56 MHz, etc.) plasmas, a very high frequency (VHF) plasma operated at 162 MHz with a multi-tile push-pull plasma source has been used in nitriding the SiO2 layer at room temperature and the effects of the VHF (162 MHz) plasma on SiOxNy formation from a SiO2 layer and electrical characteristics of the SiOxNy formed by the plasma nitridation were investigated. The use of the VHF (162 MHz) multi-tile push-pull plasma formed ∼10 nm thick SiOxNy with a very high nitrogen percentage of ∼24% on the SiO2 layer surface. Also, when the surface roughness of the SiOxNy and electrical characteristic of MOS capacitors fabricated with the SiOxNy formed by the VHF (162 MHz) plasma were compared with those formed by a capacitively coupled plasma at 60 MHz, a lower surface roughness and much lower leakage current of MOS capacitor could be obtained.

Improving the Thermal Stability of CIGS Photovoltaic Devices

Photovoltaic devices based on the copper–indium–gallium–selenium (CIGS) materials system are limited to thermal cycles below 350 °C. This is an obstacle for making higher performance devices and a significant barrier to building multi-junction CIGS devices. High anneal temperatures lead to the diffusion of Cd from the CdS buffer layer into the CIGS absorber. Cd counterdopes the absorber causing the space charge region to extend to the back contact, dramatically reducing the power conversion efficiency. This article studies the effect of a silicon oxynitride diffusion barrier placed between the absorber and buffer layers. The oxynitride film was deposited by plasma-enhanced atomic layer deposition. Capacitance–voltage and drive-level-capacitance methods were used to extract the carrier profile in the absorber as a function of anneal condition and barrier layer thickness. Both measurement techniques showed that the barrier significantly retards diffusion, leading to intact devices at anneal temperatures as high as 450 °C. The barrier conducts current through the Poole–Frankel mechanism and did not increase the device series resistance if it was 4.4 nm or thinner. The deposition of the barrier layer, however, remains a significant obstacle. Exposure of the CIGS absorber to a plasma introduced moderate damage, but exposure to a hydrogen-containing plasma led to severe loss of Se near the absorber surface. Such devices were nearly ohmic, suggesting a high concentration of deep states in the space charge region.

Luminescence Mechanism in Amorphous Silicon Oxynitride Films: Band Tail Model or N-Si-O Bond Defects Model

Silicon oxynitride films are one kind of important gate dielectric materials for applications in the fabrication of silicon CMOS integrated circuits (ICs), which have been widely and deeply studied. However, with the significant demand of the technologies for Si-based monolithic optoelectronic ICs, the research efforts on the optoelectronic applications of these materials have been continually increasing, particularly in the study of light emission properties and recombination mechanisms. In this paper, we first briefly outline the present photoluminescence (PL) mechanisms in amorphous silicon oxynitride (a-SiOxNy) films. Since the PL properties and recombination processes are affected by both structural disorder and chemical disorder, the PL mechanism has been still unclear and even controversial until now. Among these various PL recombination models, the band tail states and defect states models have gained general consensus. Recently a N-Si-O bond defect model has been reported, which depends on relative atom concentration of oxygen and nitrogen in the silicon oxynitride materials. It has been revealed that oxygen bonding plays a key role not only in reducing the structural disorder, but also in creating N-Si-O (Nx) defect states in the band gap. The characteristics of two models, namely band tail and N-Si-O bond defects, have been discussed in detail. Finally it has been shown that by controlling the chemical composition of these non-stoichiometric silicon oxynitride materials, the optical and electronic properties can be improved.

Periodic density fluctuations in sputtered aluminum‐doped silicon oxynitride layers

AbstractMagnetron sputtering is widely used for deposition of silicon oxynitride (SiOxNy) coatings on glass in large‐area applications. Since repeated deposition simulates the factory‐scale in‐line processing, amorphous aluminum‐doped SiOxNy layers with thickness of about 250 nm were deposited by reactive pulsed DC sputtering in a multi‐pass process with repeated linear movement of a glass substrate under an Al‐alloyed Si target. Using specular X‐ray reflectivity we show periodic fluctuations of the material density throughout the entire thickness of the resulting coating. The number of periods corresponds to the number of passes of the substrate through the plasma of the magnetron. Fitting results suggest a model consistent with a periodic alternation of the O/N ratio. These subtle stoichiometric fluctuations in the SiOxNy layer composition were confirmed by scanning transmission electron microscopy analysis with nanoscale resolution, and with detailed elemental maps of characteristic X‐rays of the layered cross‐section. Our study demonstrates the superior sensitivity of the relatively simple nondestructive X‐ray reflectivity method for industrial line‐process inspection compared to ellipsometry.

A Review: Preparation, Performance, and Applications of Silicon Oxynitride Film.

Silicon oxynitride (SiNxOy) is a highly promising functional material for its luminescence performance and tunable refractive index, which has wide applications in optical devices, non-volatile memory, barrier layer, and scratch-resistant coatings. This review presents recent developments, and discusses the preparation methods, performance, and applications of SiNxOy film. In particular, the preparation of SiNxOy film by chemical vapor deposition, physical vapor deposition, and oxynitridation is elaborated in details.

Average power handling capability on SiON thin film coplanar waveguide interconnections for MMICs

In this study, we investigated the average power handling capability (APHC) of silicon-oxy-nitride (SiON) thin-film-coated coplanar waveguide (CPW) interconnections for monolithic microwave integrated circuits (MMICs). SiON thin films were prepared through very-high-frequency plasma-enhanced chemical vapor deposition at 40.68 MHz. Films prepared under various annealing conditions were studied. The microwave characteristics of CPW interconnections were analyzed for fitting to the International Technology Roadmap for Semiconductors. SiON thin films were annealed under a vacuum condition for 60 s at 700 °C, 900 °C and 1100 °C. The use of coated and annealed SiON thin films on the low-resistivity Si substrate effectively improved the substrate resistivity, reduced microwave attenuation at 1100 °C, and enhanced the APHC of CPW interconnections. These results indicate that the proposed method is suitable for application to MMICs.

Zero temperature coefficient of sound velocity in vitreous silicon oxynitride thin films

Vitreous silicon oxide (v-SiO2) shows anomalous phonon properties such as the positive temperature coefficient of velocity (TCV). Variation of the Si–O–Si bond angle between SiO4 tetrahedrons has been recognized to be the key, but the origin of TCV still remains unclear. In this study, we controlled the bond angle by doping nitrogen and measured TCV of vitreous silicon oxynitride thin films with various nitrogen concentrations using picosecond ultrasonics. TCV significantly decreases by adding a small amount of nitrogen, and it shows positive to negative values as the nitrogen concentration increases. We evaluated the bond-angle change by Fourier-transform infrared spectroscopy, which decreases with the increase in the nitrogen content. We also find that the temperature rise in nondoped v-SiO2 decreases the bond angle, leading to an increase in the sound velocity. We then reveal theoretically that the bond-angle change dominates the origin of the positive TCV. This study indicates the existence of a zero-TCV single material, and we discover that the specific content of v-SiO1.71N0.19 achieves this.