Properties Of Silicon Nitride Films Research Articles

Optical, structural and composition properties of silicon nitride films deposited by reactive radio-frequency sputtering, low pressure and plasma-enhanced chemical vapor deposition

We present a comparative study of optical properties of silicon nitride thin films deposited by reactive radio-frequency (R-RF) sputtering, low pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD). For LPCVD process, two different proportions of mixed gases were used (LPCVD (A) and LPCVD (B) processes) and PECVD deposition were conducted in three regimes: low frequency (LF), mixed frequency and high frequency. Dielectric functions were extracted from ellipsometric measurements for the wavelength range from ultraviolet to near-infrared wavelengths, spanning from 210 nm to 1690 nm. To understand how different deposition parameters affect the optical properties of thin films, additional structures and composite analysis was done by using X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, X-ray reflectometry, atomic force microscopy, reflection electron energy loss spectroscopy, Fourier-transform infrared spectroscopy and stress measurements. The series of analysis show that the influence of deposition method on optical properties is significant especially for in the range of 200 nm–400 nm. For these UV wavelengths, LPCVD (A)-deposited films give a transparency window at the shortest wavelength up to 275 nm, while R-RF-sputtering and PECVD (LF) lead to transparency windows starting up to 320 nm wavelengths. Hence, appropriate techniques and recipes should be selected to account for various peculiarities in optical and structural properties of silicon nitride films towards their potential applications in photonic and nanostructured systems.

Study on properties of silicon nitride film prepared by PECVD for solar cells

Silicon nitride film containing hydrogen is widely used as antireflection layer and passivation layer in the field of solar cell industrial production. Silicon nitride films containing hydrogen were prepared by industrial plasma enhanced chemical vapor deposition (PECVD) equipment. Fourier Transform Infrared Spectroscopy (FTIR) was used to analyze the composition of the film, to study the influence of reaction gas flow rate and high-frequency power on the composition and properties of the film, and to study the influence of silicon nitride film composition on the passivation effect of the silicon wafer through the minority carrier life of the silicon wafer, so as to clarify the direction of process adjustment in actual industrial production.

69‐1: Etch Properties of Silicon Nitride Films Using a New In‐Line Equipment with Atmospheric Glow Plasma for the OLED Flexible Display

DBD non‐thermal atmospheric pressure plasma (NAPP) is suitable for the OLED display manufacturing process using flexible substrate because it is low‐temperature atmospheric pressure process, low cost process and does not need a vacuum system. High dynamic etch rate of 220À·cm/s in Si3N4 thin films was obtained in flow rate ratio (O2/CF4) of 0.13, rf 480W, the speed of 10mm/s in a 200mm new inline NAPP system. About 5% increase of dynamic etch rate by N2 gas injection was conformed. Etch profile of Si3N4 film with patterned PR shows perfectly isotropic without undercut because the species such as CF3, COF2, F and O have low energy and chemical reaction.

Moisture barrier and bending properties of silicon nitride films prepared by roll-to-roll plasma enhanced chemical vapor deposition

In this study, we demonstrated a single-layer silicon nitride (SiNx) film deposited on polyethyleneterephthalate substrate as a moisture permeation barrier film that reduced the water vapor transmission rate (WVTR). The SiNx film was fabricated by roll-to-roll, plasma-enhanced chemical vapor deposition (R2R-PECVD) in widths as large as 500 mm. The effects of the NH3/SiH4 flow ratio on the SiNx properties were investigated according to their refractive index, optical characteristics, film density, WVTR, and chemical composition. The durability of the flexibility of the SiNx film was investigated via outer/inner bending test and cyclic bending fatigue test. The SiNx film showed excellent thickness uniformity and optical properties. At the NH3/SiH4 flow ratio of 3, the SiNx film exhibited the highest film density and the best moisture barrier performances of 1.67 × 10−3 g/m2·day. The results of the inner bending test showed that the flexibility of the SiNx film was excellent. The test results showed that the failure bending radius was 2 mm. The durable flexibility of the SiNx film was influenced by the internal residual stress and microstructure. After 10,000 cyclic inner-bending fatigue tests, no crack was observed, and the WVTR values were maintained below 2.0 × 10−3 g/m2·day. These results indicate that the single-layer SiNx film fabricated with a simple R2R PECVD has a high potential as a moisture barrier film for future flexible electronic applications.

Comparison of Passivation Property on Hydrogenated Silicon Nitrides whose Antireflection Properties are Identical

Silicon nitride (SiNx:H) films made by plasma enhanced chemical vapor deposition (PECVD) are generally used as antireflection layers and passivation layers on solar cells. In this study, we investigated the properties of silicon nitride (SiNx:H) films made by PECVD. The passivation properties of SiNx:H are focused on by making the antireflection properties identical. To make equivalent optical properties of silicon nitride films, the refractive index and thickness of the films are fixed at 2.0 and 90 nm, respectively. This limit makes it easier to evaluate silicon nitride film as a passivation layer in realistic application situations. Next, the effects of the mixture ratio of the process gases with silane (SiH4) and ammonia (NH3) on the passivation qualities of silicon nitride film are evaluated. The absorption coefficient of each film was evaluated by spectrometric ellipsometry, the minority carrier lifetimes were evaluated by quasi-steady-state photo-conductance (QSSPC) measurement. The optical properties were obtained using a UV-visible spectrophotometer. The interface properties were determined by capacitancevoltage (C-V) measurement and the film components were identified by Fourier transform infrared spectroscopy (FT-IR) and Rutherford backscattering spectroscopy detection (RBS) - elastic recoil detection (ERD). In hydrogen passivation, gas ratios of 1:1 and 1:3 show the best surface passivation property among the samples.

BUCKLING MORPHOLOGIES AND INTERFACIAL PROPERTIES OF SILICON NITRIDE FILMS DEPOSITED ON FLOAT GLASS SUBSTRATES

We report on the buckling morphologies and interfacial properties of silicon nitride films deposited on float glass substrates. The coexistence of straight-sided and telephone cord buckles can be observed in the silicon nitride films after annealing at a high temperature. The straight-sided structure is metastable and can spontaneously evolve into the telephone cord structure accompanied by the increase in the buckle width and height. The geometric parameters of various buckling structures (including the straight blister, telephone cord and their transition state) have been measured by optical microscopy and atomic force microscopy (AFM). The internal stress and interfacial adhesion of the films are evaluated and analyzed based on the continuum elastic theory. It is valid to measure the interfacial properties of thin films by simplifying the telephone cord buckle as a straight-sided structure. This measurement technique is suitable for all the film systems provided that the buckles can form in the film.

Silicon Nitride Thin Films Deposited By Reactive Gas-timing Magnetron Sputtering For Protective Coating Applications

Silicon nitride is a promising alternative to carbon based materials for protective coatings, owing to its compatibility with existing silicon-based microfabrication. The complexity of the fabrication processes and contaminations hamper fine-tuning to obtain desirable coating properties. We have explored the reactive gas-timing rf plasma sputtering technique for silicon nitride thin film deposition as an alternative method to fine-tune the film properties. The gas-timing technique controls the on-off sequence of the sputtering gas (Ar) and the reactive gas (N2) during deposition. We focus this investigation to the effect of the Ar:N2 gas timing ratio (10:0, 10:1, 10:3, 10:5, 10:7 and 10:10) on the composition, the morphology, the corrosion resistance, and the hardness properties of the films, in comparison to the films deposited by conventional reactive sputtering with Ar-N2 gas mixture. These deposited silicon nitride films were characterized by Auger electron spectroscopy, Raman spectroscopy, and atomic force microscopy. The chemical resistance was measured by the electrochemical corrosion test in sulfuric acid, while the hardness properties were obtained by nanoindentation. The results reveal that although the nitrogen content in the films increases only slightly when the N2 timing is prolonged, the corrosive current of the films decreases abruptly. A thin passivating oxidized layer is found to play a major role in the corrosion resistance. In contrast, the hardness properties exhibit a uniform variation with the N2 timing. The gas-timing sequence may induce morphological changes the underlying silicon nitride films. The highest hardness obtained by the gas-timing technique almost doubles that produced by the conventional mixed gas sputtering. Thus the reactive gas-timing technique suggests a new route to selectively control the properties of silicon nitride films with minor modification to existing microfabrication processes. Copyright © 2015 VBRI Press.

Improving optical properties of silicon nitride films to be applied in the middle infrared optics by a combined high-power impulse/unbalanced magnetron sputtering deposition technique

Silicon nitride films are prepared by a combined high-power impulse/unbalanced magnetron sputtering (HIPIMS/UBMS) deposition technique. Different unbalance coefficients and pulse on/off ratios are applied to improve the optical properties of the silicon nitride films. The refractive indices of the Si3N4 films vary from 2.17 to 2.02 in the wavelength ranges of 400-700 nm, and all the extinction coefficients are smaller than 1×10(-4). The Fourier transform infrared spectroscopy and x-ray diffractometry measurements reveal the amorphous structure of the Si3N4 films with extremely low hydrogen content and very low absorption between the near IR and middle IR ranges. Compared to other deposition techniques, Si3N4 films deposited by the combined HIPIMS/UBMS deposition technique possess the highest refractive index, the lowest extinction coefficient, and excellent structural properties. Finally a four-layer coating is deposited on both sides of a silicon substrate. The average transmittance from 3200 to 4800 nm is 99.0%, and the highest transmittance is 99.97% around 4200 nm.

Optical properties of silicon nitride films formed by plasma-chemical vapor deposition

The optical properties and structure of layers of silicon nitride deposited on silicon substrates by plasma-aided chemical vapor deposition at 300°C are studied by ellipsometry, Raman scattering, IR spectroscopy, and photoluminescence techniques. It is found that immediately after deposition the silicon nitride contains hydrogen in the form of Si-H bonds. Annealing (1100°C, 30 min) leads to dehydrogenation and densification of the nitride layer. An intense Si3N4 photoluminescence signal is detected in the green. Immediately after deposition the photoluminescence peak appears at 542 nm and annealing shifts it to shorter wavelengths.

Effects of Substrate Temperature on the Properties of Silicon Nitride Films by PECVD

Under different growth conditions, silicon nitride (SiNx) thin films were deposited successfully on Si(100) substrates and glass substrates by plasma enhanced chemical vapor deposition (PECVD). The thickness, refractive index and growth rate of the thin films were tested by ellipsometer. The surface morphologies of the thin films were investigated using atomic force microscope (AFM). The average transmittance in the visible region was over 90%.

Silicon Nitride Film by Inline PECVD for Black Silicon Solar Cells

The passivation process is of significant importance to produce high-efficiency black silicon solar cell due to its unique microstructure. The black silicon has been produced by plasma immersion ion implantation (PIII) process. And the Silicon nitride films were deposited by inline plasma-enhanced chemical vapor deposition (PECVD) to be used as the passivation layer for black silicon solar cell. The microstructure and physical properties of silicon nitride films were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), spectroscopic ellipsometry, and the microwave photoconductance decay (μ-PCD) method. With optimizing the PECVD parameters, the conversion efficiency of black silicon solar cell can reach as high as 16.25%.

Room Temperature Deposition Process for Manufacturing Silicon Nitride Films Using Pulsed Plasma and Neural Network

As a deposition layer, silicon nitride (SiN) films are widely used in manufacturing silicon solar cells. To develop a cost-effective manufacturing process, deposition processes at lower temperatures is demanded. For this purpose, we report film properties of SiN films deposited at room temperature using pulsed plasma. In particular, the effect of duty ratio, a primary control variable in the pulsed plasma, on deposition rate and ion energy is examined. In an attempt to optimize the impact of ion energy on deposition rate, an empirical neural network model is constructed. A fairly large deposition rate is reported as well as several correlations between ion energy and deposition rate.

Effect of Substrate Temperature on Properties of Silicon Nitride Films Deposited by RF Magnetron Sputtering

In the present work, we report the preparation, characterization and application of silicon nitride thin films deposited by RF magnetron sputtering on oxidized silicon substrates. The properties of the films were investigated with respect to the substrate temperature during film deposition. X-ray energy dispersive spectroscopy confirms the presence of silicon and nitrogen in the films. The X-ray diffraction results indicate that the films were amorphous when deposited without external substrate heating. On the other hand, the deposition on heated substrate (300 °C) results in weakly crystalline structure. Spectral reflectance technique was used for thickness and refractive index measurements. With substrate heating, the refractive index was observed to increase. Atomic force microscope images revealed that the films were smooth and had uniform texture. The etching characteristics of the films in buffered hydrofluoric acid at room temperature and 40 wt % potassium hydroxide at 80 °C were also investigated. Significant reduction in etch rates was observed when the films were deposited on heated substrates. Using the sputter deposited silicon nitride films, microstructures such as cantilevers and diaphragms, which are basic building blocks in micro-electro-mechanical system (MEMS) based sensors, were fabricated using micromachining techniques.

Analysis of ion energy impact on the refractive index of silicon nitride films by use of neural network model

Physical ion bombardment plays a crucial role in determining refractory properties of silicon nitride films. The duty ratio is also a critical parameter that controls the amount of radio frequency power delivered to a plasma. In this study, impacts of duty ratio-induced ion energy on the refractive index are investigated. Silicon nitride films are deposited using a pulsed-plasma enhanced chemical vapor deposition. Ion energy variables and their relationship with the refractive index are studied. We report a decrease of the refractive index with decreasing duty ratio as well as a strong relationship of the refractive index with the ratio of high (or low) ion energy to high ion energy flux. A neural network model is developed to predict the effect of ion energy parameters.

Mechanical property characterization of sputtered and plasma enhanced chemical deposition (PECVD) silicon nitride films after rapid thermal annealing

In this paper, the mechanical and fracture properties of silicon nitride films subjected to rapid thermal annealing (RTA) have been systemically tested. The residual stress, Young's modulus, hardness, fracture toughness, and interfacial strength of both sputtered and plasma-enhanced chemical vapor deposition (PECVD) silicon nitride films deposited on silicon wafers were measured and compared. The results indicated that the Young's modulus and hardness of both types of silicon nitride films significantly increased when the RTA temperature increased. Furthermore, RTA processes could also alter the state of residual stress. The initial residual compressive stress of sputtered silicon nitride film was gradually relieved, and the film became tensile after the RTA process. For PECVD silicon nitride, the tensile residual stress reached its peak after a 600 °C RTA, then dropped after further increases in RTA temperature, due to stress relaxation. The tendency of the equivalent fracture toughness was to exhibit a strong correlation with that shown in the residual stress of silicon nitride. By considering the effect of residual stress, the real fracture toughness of both types of silicon nitride films were slightly enhanced by using RTA processes. Finally, experimental results indicated that the interfacial strength of PECVD silicon nitride could also be significantly improved by RTA processes at 600–800 °C. On the other hand, the initial interfacial strength of the sputtered silicon nitride was sufficiently strong, and the RTA processes only resulted in minor improvements. The characterization flow could be applied to other brittle films, and these specific test results should be useful for improving the structural integrity and process optimization of related MEMS and IC applications.

Physicochemical, structural, and mechanical properties of Si3N4 films annealed in O2

The physicochemical, structural, and mechanical properties of silicon nitride films deposited by radio frequency reactive magnetron sputtering were investigated before and after thermal annealing in O182. As-deposited films were essentially amorphous, stoichiometric, and free from contaminants for a wide range of deposition parameters, with hardness figures ranging from 16.5–22 GPa, depending mainly on the deposition temperature. After O182 annealing at 1000 °C, films hardness converged to 21 GPa, independently of the deposition temperature, which is explained based on the crystallization of the films at this annealing temperature. Moreover, oxygen is incorporated only in 7.5 nm of the Si3N4, forming silicon oxynitride at the top surface of the film, indicating a good oxidation resistance at high temperature. Finally, the elastic strain to failure (H3/E2), which mimics the wear resistance of the film, doubles after the 1000 °C annealing. These observations show the great potential of silicon nitride as a hard coating for high temperature applications.

Surface characterization and properties of silicon nitride films prepared by ion-assisted deposition

Silicon nitride (SiN) films had been prepared at low substrate temperature (100 °C) using the ion-assisted deposition (IAD) process. The films had been analyzed by the measurement of X-ray diffraction, atomic force microscopy, Fourier transform infrared spectrometry, nano indenter, and ellipsometry. The effects of N-ion current density on the surface morphology, compositional, mechanical, and infrared optical properties of SiN thin films were investigated. The results showed that the stoichiometric Si3N4 thin film with desirable properties, such as continuous and smooth surface morphology, extremely low hydrogen content, mechanical strong, and low extinction coefficient, could be obtained by using the IAD technique.

The effect of N2 flow rate on discharge characteristics of microwave electron cyclotron resonance plasma

The properties of plasma in Ar/N2 microwave electron cyclotron resonance discharge with a percentage of N2 flow rate ranging from 5% to 50% have been studied in order to understand the effect of N2 flow rate on the mechanical properties of silicon nitride films. N2+ radicals as well as N2, N+ are found by optical emission spectroscopy analysis. The evolution of plasma density, electron kinetic energy, N2+, N2, and N+ emission lines from mixed Ar/N2 plasma on changing mixture ratio has been studied. The mechanisms of their variations have been discussed. Moreover, an Ar/N2 flow ratio of 2/20 is considered to be the best condition for synthesizing a-Si3N4, which has been confirmed in the as-deposited silicon nitride films with quite good mechanical properties by nanoindentation analyses.

Influence of Gas Flow Ratio in PE‐CVD Process on Mechanical Properties of Silicon Nitride Film

AbstractThis paper investigates the influence of gas flow ratio in the preparation of submicron‐thick silicon nitride (SiNx) films on their elastic properties. SiNx films with a thickness ranging from 0.14 to 0.69 µm were deposited by plasma‐enhanced chemical vapor deposition (PE‐CVD) onto 10‐µm‐thick single‐crystal silicon (SCS) specimens by changing the gas flow ratio of monosilane (SiH4) to ammonia (NH3) to nitrogen (N2). A uniaxial tensile tester operated under an atomic force microscope (AFM) characterized the Young's modulus of SiNx films and the fracture strength of SiNx/SCS laminated specimens. The Young's modulus of SiNx films ranged from 99.5 to 144.3 GPa, which increased with the gas flow ratio but was independent of the film thickness. Nano‐indentation tests were also carried out to examine the Poisson's ratio of SiNx films in addition to the tensile tests. The Poisson's ratio was found to be 0.19 to 0.27, on average. Auger spectroscopy revealed that an increase of the atomic content ratio of nitrogen (N) to silicon (Si) in SiNx films yielded higher elastic constants of the films. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Composition and optical properties of silicon nitride films grown on SiO 2-glass and R-Al 2O 3 substrates by reactive RF magnetron sputtering

We have grown silicon nitride (Si 3N 4) films on SiO 2-glass and R-Al 2O 3 substrates by using reactive RF magnetron sputtering deposition methods with N 2 pure gas and N 2 + Ar mixture gas. The film composition, thickness and impurities have been examined by ion beam analysis. It is shown that the films have stoichiometric composition and are free from Ar contamination, when N 2 gas was used for the film deposition. Effects of impurities on the film properties, e.g., optical properties will be discussed.