Silicon Oxynitride Research Articles

Roll-to-roll deposition of silicon oxynitride layers on polymer films using a rotatable dual magnetron system

High performance permeation barrier coatings are usually multilayer stacks consisting of inorganic and organic layers. Besides the water vapor transmission rate, the optical properties of such layers have a high importance. This contribution focuses on the deposition of silicon oxynitride as an inorganic layer. This material attracts a widespread interest due to its varying refractive index depending on its oxygen and nitrogen content. The experiments were carried out in a roll-to-roll coating machine using a rotatable magnetron system. The layers were deposited by reactive pulse magnetron sputtering using targets of 1m length. It was established that the ratio of oxygen to nitrogen in the layer was not only determined by the reactive gas mixture but also by the chosen set point of the closed loop control. Both the Secondary Ion Mass Spectrometry and the Glow Discharge Optical Emission Spectroscopy measurements revealed a vertically different composition of the SiOxNy layers. This could be supported by the simulation of the optical properties of the layers.

Enhanced transmittance of sapphire by silicon oxynitride thin films annealed at high temperatures

Silicon oxynitride (SiON) and SiO2 thin films attracted considerable attention for various applications such as anti-reflection coatings and surface passivation layers. In this report, we present the enhancement of sapphire optical transmittance by over-layer deposition of the amorphous SiON by RF magnetron sputtering, and investigation on changes in microstructure and transmittance upon high-temperature annealing ∼1373 K. A thin layer of nanocrystalline SiO2 was formed at the sapphire/film interface induced by the annealing. Remarkably, the XPS spectra revealed that the silicon-nitrogen bonds disappear in the annealed films to form a non-stoichiometric silicon oxide (SiOx) phase. The films showed high visible transmittance ∼92%, which is comparable to that of soda-lime glass due to a significant reduction in the refractive index 1.41 of the films after annealing at 1373 K.

Degradation by water vapor of hydrogenated amorphous silicon oxynitride films grown at low temperature

We report on the degradation process by water vapor of hydrogenated amorphous silicon oxynitride (SiON:H) films deposited by plasma-enhanced chemical vapor deposition at low temperature. The stability of the films was investigated as a function of the oxygen content and deposition temperature. Degradation by defects such as pinholes was not observed with transmission electron microscopy. However, we observed that SiON:H film degrades by reacting with water vapor through only interstitial paths and nano-defects. To monitor the degradation process, the atomic composition, mass density, and fully oxidized thickness were measured by using high-resolution Rutherford backscattering spectroscopy and X-ray reflectometry. The film rapidly degraded above an oxygen composition of ~27 at%, below a deposition temperature of ~150 °C, and below an mass density of ~2.15 g/cm3. This trend can be explained by the extents of porosity and percolation channel based on the ring model of the network structure. In the case of a high oxygen composition or low temperature, the SiON:H film becomes more porous because the film consists of network channels of rings with a low energy barrier.

Oxidation behavior of amorphous silicon nitride nanoparticles

Silicon oxynitride is a promising structural/functional material for high temperature applications. Silicon oxynitride can be synthesized through oxidation of amorphous silicon nitride (ASN) nanoparticles followed by a crystallization process. Oxidation of the ASN plays an important role during the synthesis. Here we investigated its oxidation mechanism in an atomic scale using experimental and modelling method. The results of Nitrogen-Oxygen analyzer and X-ray photoelectron spectroscopy indicate that a large amount of nitrogen vacancies exist in ASN, thus oxidation of ASN may include vacancy oxidation ( oxygen atoms move into the nitrogen vacancies) and replacement oxidation ( oxygen atoms replace nitrogen atoms). A model has been made to describe these two oxidation processes, from which the activation energy (Ea) of the vacancy oxidation and replacement oxidation is calculated to be 9.09kJ/mol and 118.25kJ/mol, respectively. These values agree well with Ea calculated from well-designed experiments, confirming the existence of the two different mechanisms during oxidation of ASN.

Breath figures decorated silica-based ceramic surfaces with tunable geometry from UV cross-linkable polysiloxane precursor

Little has been published so far on the fabrication of porous ceramic films by using the Breath Figure method. In this work we explored the Breath Figure method to obtain ceramics with patterned surfaces. A UV cross-linkable polysiloxane was used to produce Breath Figures with tunable pore size. Pores formation, in terms of size and distribution on the polysiloxane films, were studied as a function of the concentration of the starting solution and time before UV irradiation. The polymeric breath figures were then pyrolyzed in controlled atmosphere to obtain, through the polymer-derived ceramic, PDCs, route the corresponding ceramic preserving the original porous surface. Pyrolysis under different gases, in particular air, nitrogen and ammonia, allows obtaining films of three different ceramic materials: silicon dioxide, SiO2, silicon oxycarbide, SiOC and silicon oxynitride, SiON respectively.

Characteristics of silicon oxynitride films grown by using neutral-beams and inductively coupled plasma

The characteristics of silicon oxynitride (SiON) films grown using neutral-beam and typical plasma-enhanced chemical vapor deposition methods are compared. Neutral-beam and plasma oxynitridation processes were performed using a nitrogen neutral beam at room temperature and a nitrogen plasma at 400°C, respectively, using the same deposition system. The neutral beam was generated via the surface neutralization of the ions produced by the inductively coupled plasma. The physical and electrical properties were measured using metal-insulator‑silicon structures. The plasma SiON films showed significant plasma-induced damage, while we demonstrate that the neutral beam method is suitable for growing SiON films at room temperature without plasma-induced damage or a high thermal budget.

Role of Hydrogen and Nitrogen on the Surface Chemical Structure of Bioactive Amorphous Silicon Oxynitride Films.

Silicon oxynitride (Si-O-N) is a new biomaterial in which its O/N ratio is tunable for variable Si release and its subsequent endocytotic incorporation into native hydroxyapatite for enhanced bone healing. However, the effect of nitrogen and hydrogen bonding on the formation and structure of hydroxyapatite is unclear. This study aims to uncover the roles of H and N in tuning Si-O-N surface bioactivity for hydroxyapatite formation. Conformal Si-O-N films were fabricated by plasma-enhanced chemical vapor deposition (PECVD) onto Ti/Si substrates. Fourier transform infrared spectroscopy (FTIR) and Rutherford backscattering spectrometry (RBS) analysis indicated increased Si-H and N-H bonding with increased N content. Surface energy decreased with increased N content. X-ray absorbance near edge structure (XANES) analysis showed tetrahedral coordination in O-rich films and trigonal coordination in N-rich films. O-rich films exhibited a 1:1 ratio of 2p3/2 to 2p1/2 electron absorbance, while this ratio was 1.73:1 for N-rich films. Both Si and N had a reduced partial charge for both O- and N-rich films, whereas O maintained its partial charge for either film. O-rich films were found to exhibit random bonding SizOxNy, while N-rich films exhibited random mixing: [Si-Si]-[Si-O]-[Si-N]. Thus, hydrogen bonding limits random nitrogen bonding in Si-O-N films via surface Si-H and N-H bonding. Moreover, increased nitrogen content reduces the partial charge of constituent elements and changes the bonding structure from random bonding to random mixing.

Transmission of oxygen radicals through free-standing single-layer and multilayer silicon-nitride and silicon-dioxide films

Free radicals from processing plasmas are known to cause damage to dielectric films used in semiconductor devices. Many radicals are highly reactive and can readily interact with the material exposed to the plasma. This can modify the chemical structure of the material causing deterioration of electrical and mechanical properties of the films. This work detects the transmission of oxygen radicals through single- and double-layer silicon-nitride and silicon-dioxide freestanding films. The films were exposed to oxygen plasma. A fluorophore dye was used to detect the oxygen radicals traversing through the films. By measuring the fluorescence of the dye before and after multiple timed-plasma exposures, the transmission properties of oxygen radicals through the material were found. The results indicate that the absorption length of oxygen radicals increases with increasing plasma exposure times for Si3N4 films because the oxygen plasma oxidizes the top layer of the film and forms a less dense silicon oxynitride layer. For SiO2 films, the absorption length was found to decrease as a function of plasma exposure time because of oxidation of the SiO2 surface which leads to the formation of a denser oxide layer on the surface of the sample.

On-Chip Ultra-High-Q Silicon Oxynitride Optical Resonators

Ultra-high-quality-factor (UHQ) optical resonators have enabled numerous fundamental scientific studies and advanced integrated photonic device technology. While free-standing devices can be fabricated from many different materials, only silica (SiO2) devices have been successfully integrated onto silicon wafers in large arrays. However, the UHQs (Q > 108) are transient, gradually decaying over time due to the presence of hydroxyl groups on the silica surface that attract water. Here, we overcome this challenge by using silicon oxynitride (SiOxNy) instead of silica. Unlike SiO2, SiOxNy presents a mixture of −OH and −F groups to the environment, thus inhibiting the formation of a high optical loss water layer. As a result, quality factors in excess of 100 million are able to be maintained for longer than 14 days with no environmental controls on device storage. Over the same time frame, quality factors for SiO2 devices stored in the same manner degraded by approximately an order of magnitude.

Enhanced quantum efficiency with magnesium doping in europium-containing silicon oxynitride phosphor

Abstract Two types of europium (Eu)-containing silicon oxynitride phosphors were prepared by the polymer-derived method via polycarbosilane and Eu acetylacetonate with/without magnesium (Mg) acetylacetonate. The influences of Mg doping on the phase structure, surface morphology, microstructure and photoluminescence property of the Eu-containing silicon oxynitride phosphor were investigated. It was found that both the phosphors had almost single crystalized particles with a β-Si 3 N 4 like major phase and a strong emission band ranging 430–440 nm. Doping a small amount of Mg ions into the Eu-containing silicon oxynitride phosphor not only enlarged the crystalline and particle sizes, but also significantly enhanced the quantum efficiency from 34.53% to 93.81%. By comparing with the pure silicon oxynitride powder, possible mechanisms for the major emission band in the region of 430–440 nm and the shoulder emission band at around 550 nm are discussed.

Normally-Off GaN-on-Si MISFET Using PECVD SiON Gate Dielectric

We have developed a silicon oxynitride (SiON) deposition process using a plasma-enhanced chemical vapor deposition system for the gate dielectric of GaN-on-Si metal-insulator-semiconductor field-effect transistors (MISFETs). The optimized SiON film had a relative dielectric constant of 5.3 and a breakdown field of 12 MV/cm. A normally-off GaN-on-Si MISFET fabricated with a 33-nm SiON gate dielectric exhibited a threshold voltage of ~2 V, an ON-resistance of 7.85 mQ · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and a breakdown voltage of ~640 V at the OFF-state current density of 1 μA/mm. The extracted interface trap density was 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> · eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> at E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> - E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> = 0.442 eV, which resulted in negligible hysteresis and excellent dynamic characteristics.

Record high efficiency of screen-printed silicon aluminum back surface field solar cell: 20.29%

We have achieved a record high cell efficiency of 20.29% for an industrial 6-in. p-type monocrystalline silicon solar cell with a full-area aluminum back surface field (Al-BSF) by simply modifying the cell structure and optimizing the process with the existing cell production line. The cell efficiency was independently confirmed by the Solar Energy Research Institute of Singapore (SERIS). To increase the cell efficiency, for example, in four busbars, double printing, a lightly doped emitter with a sheet resistance of 90 to 100 Ω/□, and front surface passivation by using silicon oxynitride (SiON) on top of a silicon nitride (SiNx) antireflection layer were adopted. To optimize front side processing, PC1D simulation was carried out prior to cell fabrication. The resulting efficiency gain is 0.64% compared with that in the reference cells with three busbars, a single antireflection coating layer, and a low-sheet-resistance emitter.

Detailed study of SiOxNy:H/Si interface properties for high quality surface passivation of crystalline silicon

In this work, we present a detailed study on the interface and passivation properties of the hydrogenated silicon oxynitride (SiOxNy:H) on the crystalline silicon (c-Si) and their correlations with the film composition. The SiOxNy:H films were synthesized by plasma enhanced chemical vapor deposition (PECVD) at various N2O flow rates, which results in different film composition, in particular the different H-related bonds, such as SiH and NH bonds. Fourier transform infrared spectroscopy measurements show that the concentration of NH bonds increases with the N2O flows from 0 to 30 sccm, while drops below the detection limit at N2O flows above 30 sccm. This changing trend of NH bonds correlates well with the evolution of carrier lifetime of silicon substrate passivated by SiOxNy:H film, indicating the crucial role of NH bonds in surface passivation. It is inferred that during the film deposition and forming gas anneal (FGA) a considerable amount of hydrogen atoms are liberated from the weak type of NH bonds rather than SiH bonds, and then passivate the dangling bonds at the interface, thus resulting in the significant reduction of interface state density and the improved passivation quality. In detail, the interface state density is reduced from ∼5 × 1012 to ∼2 × 1012 cm−2 eV−1 after the FGA, as derived from the high frequency capacitance-voltage (CV) measurements.

New design graded refractive index antireflection coatings for silicon solar cells

Reflectance spectrum of nanoporous silicon dioxide (SiO2) double layer was calculated by using the matrix method. The results were compared with the corresponding spectrum of silicon oxynitride (SiO[Formula: see text]N[Formula: see text])–porous silicon (PS) double layer which deposited on nanostructured black silicon coatings. The nanoporous silicon dioxide (SiO2) double layer deposited on nanostructure black silicon antireflection coating presents a lower reflectance in a broad range of solar spectrum. This research outcome may find a wide application in solar cell industry.

Oxide-related defects in quantum dot containing Si-rich silicon nitride films

Silicon-rich silicon nitride thin films were deposited by co-sputtering silicon and silicon nitride and annealed at high temperatures to form precipitates of silicon nanocrystals within the nitride matrix. This process was chosen to replicate the typical fabrication used for silicon nitride based quantum dots. Photoluminescence (PL) spectra were observed from the silicon nitride samples after a high temperature anneal and the PL peak shifted with increasing Si concentration. However, the time resolved PL spectra exhibited a fast decay in the nanosecond range, indicating that the PL does not originate from a radiative transition due to quantum confinement in the silicon nanocrystals. The chemical composition and the structural properties of the thin films were studied using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, and Raman spectroscopy. XPS and FTIR demonstrated that there was some oxygen incorporation in the as-deposited films, forming silicon oxynitride, which increased after high temperature annealing in N2 ambient. It is proposed that the PL originates from defect states related to the increased film oxidation after high temperature annealing and the shift in PL peak energies are due to transitions between the defect levels and the band edges of the nitride matrix.

Broad range refractive index engineering of SixNy and SiOxNy thin films and exploring their potential applications in crystalline silicon solar cells

Silicon nitride (SixNy) and silicon oxynitride (SiOxNy) are materials that can find multifarious application in solar cells by tuning their microstructure and optical properties. In this work we have investigated a series of SixNy and SiOxNy films deposited by rf-PECVD at a low temperature of 200 °C having different compositional and optical properties by changing the gas mixture ratio during deposition resulting in varying refractive index materials. The effect of varying gas ratio on the composition of these materials has been investigated comprehensively by X-ray Photoelectron Spectroscopy (XPS) and the bond analysis using Fourier Transform Infrared Spectroscopy (FTIR) thereby creating a material library to select materials of desired properties and bond composition for specific applications in solar cells. The structural and optical properties were also analysed using Micro-Raman spectroscopy, X-ray Diffraction (XRD), UV-VIS-NIR spectrophotometer and ellipsometry. The films were found to be amorphous, hydrogenated, compact, presents high deposition rates and needs lesser thermal budget. In order to demonstrate their multifaceted application potential, we have fabricated multilayer anti-reflection coatings (ARC), novel Rugate ARC, dielectric Bragg mirrors using SiOxNy/SixNy multi layers as back reflectors for thin crystalline silicon (c-Si) wafers as well as the passivation of c-Si. The novel bilayer passivation stack over CZ p-type c-Si wafers using SiOxNy/SixNy presented a minority carrier lifetime of 169 μs with an implied Voc of 673 mV.

One-Step Synthesis of Silicon Oxynitride Films Using a Steady-State and High-Flux Helicon-Wave Excited Nitrogen Plasma

A steady-state and high-flux helicon-wave excited N2 plasma was used to oxynitride Si substrates for the synthesis of silicon oxynitride (SiON) films. X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) have been extensively used to characterize surface quality of the SiON films, and it is found that a large amount of nitrogen (N) can be incorporated into the films. The result of XPS depth profiles shows that the N concentration is high near the surface and the oxide/Si interface. In the UPS spectra, absence of the reappearance of surface states suggests a resistance to clustering of the oxynitride layer. The N2 flux and Ar mixture quantity can facilitate tuning of the dissociation characteristics in N2 discharge. By modulating the N2 fractions, the N+ density reaches maximum at a N2/(N2 + Ar) flow-rate ratio of 0.5, resulting in incorporation of more N atoms into the SiON films. Considering the easy control of N2 plasma, our work opens up a new avenue for achieving high-yield SiON films at low temperature.

Effects of silica sol on the preparation and high-temperature mechanical properties of silicon oxynitride bonded SiC castables

Abstract Silicon oxynitride bonded SiC castables (SS castables) were prepared via in-situ nitridation at 1420 °C for 6 h in flowing N 2 , using black SiC, SiO 2 fume and Si powder as starting materials, and silica sol as a binder. Phase compositions and microstructures of as-prepared SS castables were characterized, and the effects of silica sol's type and amount on their cold and hot moduli of rupture (CMOR and HMOR) and thermal shock resistance examined and discussed. The results indicated that using silica sol containing well-dispersed spherical SiO 2 nanoparticles as a binder not only resulted in improved workability of fresh castables and packing density of green samples, but also promoted the in-situ formation of Si 2 N 2 O bonding phase on nitridation. HMOR at 1400 °C of nitrided SS castables using 7 wt% silica sol was as high as 51 MPa, and their residual strength after one thermal shock cycle (1100 °C-room temperature) remained significantly higher than their CMOR value before the thermal shock. It is believed that the in-situ formed Si 2 N 2 O in the castables was responsible for the much improved cold/hot strength and thermal shock resistance.

Device performance enhancement via a Si-rich silicon oxynitride buffer layer for the organic photodetecting device

An advanced organic photodetector (OPD) with a butter layer of Si-rich silicon oxynitride (SiOxNy) was fabricated. The detector structure is as follows: Indium tin oxide (ITO) coated glass substrate/SiOxNy(10 nm)/naphthalene-based donor:C60(1:1)/ITO. Values of x and y in SiOxNy were carefully controlled and the detector performances such as dark current and thermal stability were investigated. When the values of x and y are 0.16 and 0.66, the detector illustrates low dark current as well as excellent thermal stability. In the OPD, silicon oxynitride layer works as electron barrier under reverse bias, leading to the decrease of dark current and increase of detectivity. Since the band gap of silicon oxynitride unlike conventional buffer layers can also be controlled by adjusting x and y values, it can be adapted into various photodiode applications.

Vibrational and dielectric properties and ideal strength of Si2N2O ceramic from first principles

Abstract Silicon oxynitride (Si 2 N 2 O) is a functional ceramic having many possible applications. In this work, we studied the vibrational and dielectric properties and ideal strength as well as the related deformation mechanism of Si 2 N 2 O using first principles calculations. Factor group analysis was performed and vibrational frequencies were calculated to assign the observed vibrational modes. Infrared dielectric and absorption spectra were simulated and their origins were revealed. Tensile, compressive and shear strengths along the representative directions were investigated, which gave Si 2 N 2 O an ideal strength agreeing well with its experimental hardness. The calculated minimum compressive stress also coincides well with the starting amorphization pressure observed in shock experiments, providing a theoretical method to study mechanical effects of shock wave. Analyses on the deformation mechanisms at the critical strains imply that Si-O bond is stronger than other bonds, which is opposite to the previous speculation.