Structure Of Silicon Nitride Research Articles

Fabrication of humidity monitoring sensor using porous silicon nitride structures for alkaline conditions

Porous silicon nitride structures were fabricated for a humidity sensor. The porous silicon structures were fabricated by the metal-assisted chemical etching process, and the conformal silicon nitride thin film was deposited by the atomic layer deposition process. The optimized porous sensor with the 10 nm-thick silicon nitride thin film had a hydrophilic surface and compared to other sensors, had an excellent humidity sensing response. Especially, it showed a superior humidity sensing response at 1 kHz with fast response and recovery times of 13.3 s and 12.4 s, respectively, were observed. Based on the electrochemical impedance spectroscopy results, the equivalent circuits and humidity sensing mechanism were discussed. The chemical stability of the silicon nitride was characterized using Tafel analysis in alkaline electrolytes. Additionally, the sensor's humidity sensing capabilities were tested under cement-embedded conditions.

Mid-infrared bimodal wide metamaterial absorber based on double-layer silicon nitride structure

Infrared band occupies a very important position in the electromagnetic wave band. Traditional infrared devices use the inherent properties of natural materials to achieve the regulation of electromagnetic waves, but the limited ability of such devices to regulate electromagnetic waves can't well meet our needs. In this paper, we reported a metamaterial absorber of Cr-Si3N4-Cr-Si3N4-Ti based on double-layer metal-insulator-metal (MIM). It is investigated with the optimal structural parameters of 490 nm, 330 nm, 30 nm, 720 nm, 120 nm, in descending order, at which the absorptive properties are studied. When the light wave is incident vertically, it can be obtained from the experimental simulation that this absorber has polarisation insensitivity. Because of the coupling effect of the surface plasmon resonance and the high-loss material, the bandwidth of absorption greater than 90% can reach 9190 nm, and the average absorption in the target long-wave infrared band (9.506∼18.145 μm) is 94.8%. By selecting different geometrical parameters of the structure, the absorption spectrum can be adjusted independently. In addition, the absorber has good incident angle insensitivity in TE and TM modes. Also, the absorber we proposed has a plain structure, is convenient for manufacturing, the material is easier to obtain, which ensures a good absorption bandwidth and average absorptivity, and the study of this metamaterial absorber has important applications in solar cells, satellite radiothermographs, photodetectors, and spectral imaging.

Registration of Functioning of a Single Horseradish Peroxidase Macromolecule with a Solid-State Nanopore

Currently, nanopore-based technology for the determination of the functional activity of single enzyme molecules continues its development. The use of natural nanopores for studying single enzyme molecules is known. At that, the approach utilizing artificial solid-state nanopores is also promising but still understudied. Herein, we demonstrate the use of a nanotechnology-based approach for the investigation of the enzymatic activity of a single molecule of horseradish peroxidase with a solid-state nanopore. The artificial 5 nm solid-state nanopore has been formed in a 40 nm thick silicon nitride structure. A single molecule of HRP has been entrapped into the nanopore. The activity of the horseradish peroxidase (HRP) enzyme molecule inserted in the nanopore has been monitored by recording the time dependence of the ion current through the nanopore in the course of the reaction of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) oxidation reaction. We have found that in the process of ABTS oxidation in the presence of 2.5 mM hydrogen peroxide, individual HRP enzyme molecules are able to retain activity for approximately 700 s before a decrease in the ion current through the nanopore, which can be explained by structural changes of the enzyme.

FDTD investigation of adiabatic optical coupling between Silicon nitride and Germanium-based optical structures for energy-efficient photonic integration

This paper aims to investigate the potential of a direct integration between Si3N4 waveguides and Germanium(Ge)-based structures, which are considered two of the most promising silicon(Si)-compatible materials for passive and active functions for Si-based energy-efficient photonics, respectively. This paper focuses on investigating the vertical coupling scheme between these materials employing a tapered structure of the Ge-based layer using 2D FDE and 3D FDTD simulations, to match the optical mode from a passive Si3N4 waveguide to the Ge-based layer and vice versa. The expected optical coupling performance will be reported, and its dependence on the unavoidable fabrication variation in the coupling region will be also investigated. Additionally, the coupling performance of the vertical coupling approach compared to the previous investigation between a Si waveguide and a Ge layer will be addressed.

STM/STS Study of the Density of States and Contrast Behavior at the Boundary between (7 × 7)N and (8 × 8) Structures in the SiN/Si(111) System

The origin of the contrast appearing in STM images at the boundary between diverse ordered structures is studied using the example of two structures, (7 × 7)N and (8 × 8), formed in the system of a two-dimensional silicon nitride layer on the Si(111) surface during ammonia nitridation. A significant dependence of the contrast between these structures on the voltage applied to the tunnel gap was found and studied both experimentally and theoretically. Variations in the contrast were quantitatively studied in the range from −3 V to +3 V, and they were studied in more detail for the positive biases on the sample from +1 V to +2.5 V, where the contrast was changed more than 2 times. Within the one-dimensional Wentzel–Kramers–Brillouin (WKB) model for the tunnel current, a comparatively simple procedure is proposed for the correction of the experimental STS-spectra of differential conductivity to identify the adequate (feasible) density of electron states (DOS). It is shown that the (8 × 8) structure DOS corresponds to a graphene-like layer of silicon nitride structure. The proposed correction procedure of the empirical differential conductivity spectra measured by STS will be useful for the quantitative determination of the DOS of new two-dimensional materials and surface structures.

Enhanced sensitivity of surface plasmon resonance biosensor for the selective detection of immunoglobin (IgG)

In this work, we propose a surface plasmon resonance (SPR) biosensor based on a hybrid structure of silicon nitride (Si3N4), molybdenum trioxide (MoO3), and graphene oxide (GO) in the Kretschmann configuration. To investigate the performance parameters of the SPR biosensor, we calculate, theoretically, the reflectance spectra of the proposed model and analysed it. The investigation of various performance parameters i.e., sensitivity, detection accuracy, and quality factor, of sensor configuration are theoretically done with the optimized thickness of silver (55 nm), silicon nitride (5 nm), molybdenum trioxide (10 nm), and graphene oxide (2.55 nm) respectively. The sensitivity, detection accuracy, and figure of merit for the proposed SPR structure are found at 301 deg./RIU, 4.01, and 133 RIU−1 respectively for the detection of IgG. Furthermore, the present SPR biosensor shows improved sensitivity as compared to the other reported works. The refractive index of the analyte changes from 1.33 to 1.37 due to adsorption of the analyte at the GO surface. The proposed sensor design can detect the small change in the refractive index of the sensing media doped with the analyte.

A SiGe Slot Approach for Enhancing Strain Induced Pockels Effect in the Mid-IR Range

Strained silicon was proposed more than a decade ago promising to revolutionize the silicon photonics field by allowing efficient modulation in this platform. Despite all the efforts, still rather low χ(2) values have been measured in strained silicon devices. In addition, the way of applying strain has not barely changed since the concept was proposed, usually consisting on a silicon waveguide covered by a stressor material such as silicon nitride. In this letter, a SiGe slot approach is explored as a different route to enhance the strain induced Pockels effect in the mid-IR range. Such approach would allow effective index change values which are near to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> and improve the values expected for the most common silicon - silicon nitride structure by more than three orders of magnitude.

Defects induced by He+ irradiation in γ-Si3N4

Formation and evolution of defect levels in the electronic structure of silicon nitride with cubic spinel structure, γ-Si3N4, after the irradiation with He+ ions was investigated using spectroscopic techniques. Strong changes of cathodoluminescence (CL), photoluminescence (PL), photoluminescence excitation (PLE) and Raman spectra were detected. In particular, excitonic PL was significantly inhibited and a new near-IR band appeared with the band gap excitation hν≥Eg = 5.05 eV. This was explained by an effective trapping of photoinduced electrons and holes by charged defects. The spectral shift of PL with the excitation photon energy indicated heterogeneous nature of the defect sites. The energetic position of near-IR and visible PL bands correlate, suggesting an interaction with the common cation defect to be an origin. The visible PL of exciton bound to a neutral defect Si× was red shifted, which was attributed to the permutations between empty and occupied octahedral and tetrahedral sites, inherent to the spinel structure, after collisions with He+ ions. The positively charged cation sites in the spinel structure are compensated by VN‴ anion vacancies. The local deformation of the spinel lattice affects PL intensity of the self-trapped exciton at 4.35 eV.

Структура нитрида кремния, полученного плазмохимическим синтезом.

X-ray diffraction results of short-range order in nanoscale powders of silicon nitride obtained by plasma-chemical synthesis are presented. It is shown that the most probable structure of nanopowder silicon nitride can be characterized by a model of a disordered network of SiN4tetrahedra.

Investigation of the Effect of Atomic Composition on the Plasma-Chemical Etching Rate of Silicon Nitride in High-Power Transistors Based on an AlGaN/GaN Heterojunction

The effect of atomic composition on the rate of the plasma-chemical etching of silicon nitride in high-power transistors based on an AlGaN/GaN heterojunction is studied. It is shown how the subsequent process of its plasma-chemical etching depends on the configuration of the incorporation of hydrogen impurity atoms into the molecular structure of silicon nitride deposited in the plasma. The dependence of the etching rate on the process parameters (the working pressure in the chamber, the plasma-generator power, the working-gas flows, and the deposition temperature) is investigated. It is shown that the etching rate of the HxSirNzHy film is independent directly on the hydrogen content but significantly depends on the ratio of [Si–H]/[N–H] bonds. The etching rate of HxSirNzHy in high-density plasma at low powers is much less dependent on the configuration of hydrogen bonds than the etching rate of this dielectric in a buffer etchant.

Novel fabrication of fixed suspended silicon nitride structure for MEMS devices with dry etching

A method of fabricating suspended LPCVD and PECVD silicon nitride structure is demonstrated for a wide range of MEMS (Micro-Electro-Mechanical Systems) applications. Low stress LPCVD and PECVD silicon nitride film of 1 μm thickness were selected for the structure separately. Optical Lithographic parameters, viz, photoresist (PR) thickness, PR variety and baking parameters were optimized to obtain the PR suitable for selective etching of silicon and silicon nitride. Parameters of the dry etching process were also optimized to achieve anisotropic etching of silicon nitride and isotropic etching of Si to release the silicon nitride beam. The silicon nitride structures, thus released, were characterized using Scanning Electron Microscope (SEM) and Laser Doppler Vibrometer (LDV). Finite Element Method (FEM) analysis was carried out using COMSOL, to compare with the experimental modes of vibration investigated using the Laser Doppler Vibrometer (LDV). Thus we demonstrate that the first mode at 30 kHz was indeed the optimum match.

Effect of SiO2 Etching Inhibitor to H3PO4 for the Selective Si3N4 Wet Etching of 3D NAND

3D NAND has a vertically stacked semiconductor structure to increase the memory density of semiconductor devices. 3D NAND devices are based on the multiply stacked silicon nitride (Si3N4) and silicon dioxide (SiO2) structure, and it is essential to high selectively etch Si3N4-to-SiO2 in the fabrication process. Hot phosphoric acid (H3PO4) has been typically used in the Si3N4-to-SiO2 selective etching process and the etch selectivity can increase by adding SiO2 etching inhibitors in H3PO4. In order to increase etching rate of Si3N4 and Si3N4-to-SiO2 etch selectivity, additives can be added in H3PO4. However, SiO2 etching inhibitors to increase Si3N4-to-SiO2 etch selectivity may occur by-product redeposition issue around the SiO2-layered trenches of Si3N4/SiO2 multi-stack structure. In this study, the etching behavior of the Si3N4/SiO2 multi-stack structures in SiO2 etching inhibitor-added H3PO4 was investigated. In addition, high selective Si3N4 etching with the control of redeposition was performed on the Si3N4/SiO2 multi-stack structure by adding proper SiO2 etching inhibitor in H3PO4.

Integration of nanodiamonds with NV-centers on optical silicon nitride structures

In this work we had developed optical structures from silicon nitride for further integration of the nanodiamonds containing NV-centers with them. We have introduced method of the nanodiamonds solution application on the substrates. The work has practical meaning in nanophotonics sphere and in development of optical devices with single-photon sources.

29Si NMR Chemical Shifts in Crystalline and Amorphous Silicon Nitrides.

We investigate 29Si nuclear magnetic resonance (NMR) chemical shifts, δiso, of silicon nitride. Our goal is to relate the local structure to the NMR signal and, thus, provide the means to extract more information from the experimental 29Si NMR spectra in this family of compounds. We apply structural modeling and the gauge-included projector augmented wave (GIPAW) method within density functional theory (DFT) calculations. Our models comprise known and hypothetical crystalline Si3N4, as well as amorphous Si3N4 structures. We find good agreement with available experimental 29Si NMR data for tetrahedral Si[4] and octahedral Si[6] in crystalline Si3N4, predict the chemical shift of a trigonal-bipyramidal Si[5] to be about −120 ppm, and quantify the impact of Si-N bond lengths on 29Si δiso. We show through computations that experimental 29Si NMR data indicates that silicon dicarbodiimide, Si(NCN)2 exhibits bent Si-N-C units with angles of about 143° in its structure. A detailed investigation of amorphous silicon nitride shows that an observed peak asymmetry relates to the proximity of a fifth N neighbor in non-bonding distance between 2.5 and 2.8 Å to Si. We reveal the impact of both Si-N(H)-Si bond angle and Si-N bond length on 29Si δiso in hydrogenated silicon nitride structure, silicon diimide Si(NH)2.

Material Structure and Mechanical Properties of Silicon Nitride and Silicon Oxynitride Thin Films Deposited by Plasma Enhanced Chemical Vapor Deposition

Silicon nitride and silicon oxynitride thin films are widely used in microelectronic fabrication and microelectromechanical systems (MEMS). Their mechanical properties are important for MEMS structures; however, these properties are rarely reported, particularly the fracture toughness of these films. In this study, silicon nitride and silicon oxynitride thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) under different silane flow rates. The silicon nitride films consisted of mixed amorphous and crystalline Si3N4 phases under the range of silane flow rates investigated in the current study, while the crystallinity increased with silane flow rate in the silicon oxynitride films. The Young’s modulus and hardness of silicon nitride films decreased with increasing silane flow rate. However, for silicon oxynitride films, Young’s modulus decreased slightly with increasing silane flow rate, and the hardness increased considerably due to the formation of a crystalline silicon nitride phase at the high flow rate. Overall, the hardness, Young modulus, and fracture toughness of the silicon nitride films were greater than the ones of silicon oxynitride films, and the main reason lies with the phase composition: the SiNx films were composed of a crystalline Si3N4 phase, while the SiOxNy films were dominated by amorphous Si–O phases. Based on the overall mechanical properties, PECVD silicon nitride films are preferred for structural applications in MEMS devices.

Ion-beam formation of light-emitting structures based on silicon nitride layers on silicon

The paper shows the advantage of silicon nitride for use as a light-emitting element in integrated circuits. Alongwith this, the chosen methods for obtaining the studied samples enable us to determine all possible causesresponsible for radiative recombination. The effect of irradiation with Xe+ ions of 200 MeV in the dose range109 – 1014 ions/cm2 on the optical properties and the structure of silicon enriched silicon nitride (SRN) filmsdeposited on the Si substrate by chemical vapor deposition under low pressure was studied. Based on the Ramanscattering (RS) data, it was concluded that the irradiation by 200 MeV Xe ions with a dose of 1×1014 ions/cm2leads to the dissolution of the amorphous Si phase in the nitride matrix. According to the results of transmissionelectron microscopy, preliminary irradiation with swift heavy ions (SHI) enhances the phase separation processin the nitride layer with a 22% excess of Si during the subsequent annealing at 1100°C for 60 minutes. The SHIirradiation, followed by the heat treatment, leads to a further increase in the intensity of the photoluminescence(PL) in the spectral range 600–750 nm compared with that in case of annealed films without preliminaryirradiation. It is known that radiation in this spectral range is due to Si nanocrystals (Si NCs).

Fabrication and characterization of micromechanical bridges with strain sensors deposited using focused electron beam induced technology

In this paper we present a method of fabrication and characterization of strain sensors fabricated with a focused electron beam induced deposition (FEBID) technology from Pt precursor. The FEBID structures were used as deflections sensors and applied to read-out resonance frequency of micromechanical bridges. In our experiments we have investigated silicon nitride structures with an integrated metallization path on which the FEBID strain sensors were deposited. In order to modify mechanical properties of the microbridge we developed and applied a focused ion beam (FIB) milling technology which allowed to modify the distribution of mechanical stress and consequently increase the deflection detection sensitivity. An atomic force microscopy (AFM) technology was applied to both characterize the electrical properties of the deposited structures and characterize properties of the fabricated devices. In this way the gauge factor (GF) of the FEBID fabricated nanogranular resistors (NGRs) of 4.25 was determined for the static microbridge deflection.

Quasiatomic layer etching of silicon oxide selective to silicon nitride in topographic structures using fluorocarbon plasmas

The precision etch of dielectric materials (SiO2, Si3N4) in self-aligned contacts and self-aligned multiple patterning at the 10 nm technology node and beyond is required to solve/mitigate the trade-offs of selectivity, profile, and aspect ratio independent etching. Atomic layer etching (ALE) has significant potential to solve the trade-offs challenge. Unlike the halogenation step of atomic layer etching of silicon using chlorine (e.g., chlorine adsorption on c-Si), the fluorocarbon deposition step of ALE of nitride and oxide is not a self-limiting process. The argon ion bombardment step used to remove CF polymer layer and activated layer of oxide and nitride can be self-limiting if ion energy is kept below the sputter threshold. In this paper, the authors will discuss concurrent engineering approaches including both modeling and experimentation that can provide visibility to the parameters characterizing a viable process. The core of the approach is a new integrated chamber hybrid plasma equipment model-feature scale Monte Carlo feature profile model for silicon dioxide etch experiments intended to be selective to organic planarization layer masked silicon nitride structures. The experiments were conducted on a dual frequency capacitively coupled plasma source using a benchmark Ar/C4F6 chemistry for adsorption and an argon plasma step for desorption in the cyclic etch process. The concurrent engineering approach comprises stages of simulation development and prediction tests using both blanket wafer and patterned wafer data, and finally, process parameter optimization. Plasma parameters for each of the fluorocarbon layer adsorption and desorption etch steps are presented. The authors show how nitride/oxide etch selectivity can be optimized using saturation, “S”-curves, and detail pattern top clogging and its correlation with mask topography. S-curves describe etch/deposition rate trends as a function of desorption time in cyclic etch processes. The results show that clogging margin is a sensitive function of desorption time and feature topography.

The influence of carbon on the structure and photoluminescence of amorphous silicon carbonitride thin films

Silicon carbonitride (SiCN), an intermediate structure between silicon carbide and silicon nitride, has emerged as a material of interest to increase the performance of silicon-based visible luminescence. In this work, thin films of SiCN were deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition using silane, nitrogen, and methane as the gas precursors. The microstructure, composition, and optical properties of the SiCN layers were determined by elastic recoil detection, Rutherford backscattering spectrometry, ultraviolet–visible spectroscopy, variable angle spectroscopic ellipsometry, photoluminescence, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, and X-ray diffraction spectroscopy techniques. The optical and electrical characteristics were linked with the structural properties to investigate the effect of carbon incorporation on the nature of SiCN thin films. Successive increases in the carbon content from 0 to 41.6at.% resulted in an increase in refractive index and growth rate of the films, while band gap narrowing occurred. Structural studies showed that carbon preferred to form bonds with silicon rather than nitrogen in SiCN thin layers. The produced films contained mainly amorphous silicon nitride and silicon carbide structures and small amounts of an amorphous SiCN network. Photoluminescence emission showed two peaks centred at 475 and 550nm. The observed link between the photoluminescence behavior and the composition and structure of SiCN layers revealed the details of the most luminescent SiCN thin film. Silicon nitride (carbon-free) thin films exhibited lower emission intensities indicating that the presence of carbon in the silicon nitride matrix enhanced the visible light emission.

Organosilicon polymer-derived mesoporous 3D silicon carbide, carbonitride and nitride structures as platinum supports for hydrogen generation by hydrolysis of sodium borohydride

Herein, mesoporous 3D silicon carbide (SiC), carbonitride (SiCN) and nitride (Si3N4) structures have been synthesized by nanocasting and pyrolysis using commercial organosilicon polymers as precursors of the different compositions. Detailed characterizations by BET and XRD allowed us to fix the most appropriate parameters to design mesoporous 3D structures with high specific surface areas and high pore volume. Then, the series of 3D structures has been used as supports to grow platinum nanoparticles (Pt NPs) by wet impregnation followed by reduction in hydrogen/argon flow. The Pt-supported mesoporous 3D supports kept the mesoporosity of the virgin supports to be used for catalytic hydrolysis of sodium borohydride (NaBH4). A hydrogen generation rate of 24.2 L min−1 gPt−1 is measured for the Pt-supported mesoporous 3D Si3N4 structure, which is notably higher than the catalytic hydrolysis using Pt-supported mesoporous 3D SiC and SiCN structures. HRTEM investigations demonstrated the homogeneous distribution of Pt NPs over the Si3N4 support.