Dielectric Silicon Nitride Research Articles

Real-Time Cell Temperature Fluctuation Monitoring System Using Precision Pt Sensors Coated with Low Thermal Capacity, Low Thermal Resistance, and Self-Assembled Multilayer Films.

Real-time monitoring of cell temperature fluctuation can help researchers better understand physiological phenomena and the effects of drug treatment on cells, which is a novel and important tool for cellular informatics. The platinum (Pt) temperature sensor is widely used in temperature measurement with the advantages of strong stability, great accuracy, and high sensitivity. However, the commercially available Pt sensors have large thermal resistance and heat capacity which are difficult to be applied for cell temperature measurement because only a very small amount of heat flux is generated by live cells. In this study, we designed a system using precision Pt thin-film temperature sensors with low heat capacity and thermal resistance. The Pt thin-film sensors are covered by a silicon nitride insulation layer grafted with a self-assembled multilayer silane film for promoting cell adhesion. The temperature coefficient of resistance of the Pt temperature sensor was about 2100 ppm/°C. The four-wire lead design next to the sensor detection area ensured maximum accuracy, resulting in a system noise below 0.01 °C over a long time. HEK-293T and HeLa cells were cultured on the sensor surface, respectively. The temperature fluctuation of 293T cells was monitored in a cell culture medium, showing a temperature increase of about 0.05-0.12 °C. The temperature fluctuation of HeLa cells treated with cisplatin was also measured and recorded, indicating a temperature decrease of 0.01 °C first and then a gradual temperature increase of 0.04 °C. The Pt sensor system we developed demonstrated high sensitivity and long stability for cell temperature fluctuation monitoring, which can be widely used in cell activity and cellular informatics studies.

High thermoelectric power factors in sputter-deposited polycrystalline n-type BaSi2 films

We formed n-type polycrystalline semiconducting BaSi2 films on insulating silicon nitride films by sputtering and investigated their electrical and thermoelectric properties. The electron concentration of the grown films was approximately 1015–1016 cm−3 at room temperature, and the electron mobility was higher than 103 cm2 V−1 s−1 despite the polycrystalline films being randomly oriented. The films contained a large concentration of oxygen (1.5 × 1021 cm−3). A large thermoelectric power factor of 386 μW m−1 K−2 was obtained at 309 K for B-doped n-BaSi2 films. This value is approximately 8.6 times higher than the previous highest power factor reported for n-BaSi2.

Effect of Gate Dielectric Material on the Electrical Properties of MoSe2-Based Metal–Insulator–Semiconductor Field-Effect Transistor

In this study, we fabricated metal–insulator–semiconductor field-effect transistors (MISFETs) based on nanolayered molybdenum diselenide (MoSe2) using two insulator materials, silicon dioxide (SiO2) and silicon nitride (SiN). We performed morphological and electrical characterizations in which the devices showed good electronic performance, such as high mobility and high Ion/Ioff ratios exceeding 104. The subthreshold swing (ss) was somewhat high in all devices owing to the dimensions of our devices. In addition, the transfer curves showed good controllability as a function of gate voltage. The photogating effect was weakened in MoSe2/SiN/Si, indicating that SiN is a good alternative to silicon oxide as a gate dielectric material.

Corrosion and Protection of Silicon Nitride Insulators in Microelectrode Array Applications

In the study of the electrophysiological activity of cultured cells, the integrity of the electrical insulation layer is crucial in ensuring the reliability of microelectrode array (MEA) sensor measurements. The materials used are required to withstand the challenging culture conditions for up to several months. The commonly used silicon nitride (SiN) has been reported to corrode in cell cultures with very little attention in the scientific community. Herein, we show that plasma-enhanced chemical vapor deposited (PECVD) SiN is subject to substantial wear when in contact with different culture media, with the corrosion rate depending on the deposition temperature and media type. A chemically stable insulator is proposed and demonstrated as an alternative for SiN using thermally annealed atomic layer deposited (ALD) titanium dioxide (TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) as a transparent protective layer for SiN. Electrochemical impedance spectroscopy (EIS) was successfully applied to periodically assess the integrity and thickness of the insulation layers in two different media, with profilometer measurements performed as an endpoint analysis to confirm the actual change in thickness in four solutions. ALD TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> not only prevented insulator corrosion but also showed excellent cytocompatibility during a four-week culture with human embryonic stem cell (hESC)-derived neurons. The results here underline the need for addressing the corrosion of SiN insulation in MEA sensors. We believe that the integrity and results of cellular measurements can be compromised, especially when reusing MEAs. We propose the ALD TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> protected insulator as a viable solution for this problem, as it increases reliability, particularly during extended cell cultures.

A high-precision current measurement platform applied for statistical measurement of discharge current transient spectroscopy of traps in SiN dielectrics

This paper presents a current measurement platform to measure current across dielectrics with a high-precision of 10−17 A from a large number of small capacitors at high speed. The developed platform consists of a common readout circuit part and a dielectric part formed on the circuit part by a simple process. A platform chip with 10 μm pitch 384H × 360V cells was fabricated using a 0.18 μm CMOS technology and silicon nitride (SiN) films were formed by plasma-enhanced CVD (PECVD) as a measurement target. The trap property of SiN films in metal–insulator–metal (MIM) capacitors was statistically measured by discharge current transient spectroscopy (DCTS) using the developed platform. The measured average energy levels of traps (E c –E t ) were 0.21–0.25 eV, which is in good agreement with that of the discrete samples. The distributions of energy levels and densities of traps measured with different film thicknesses and areas are also presented and discussed.

Влияние механических напряжений на поведение лазерных ультразвуковых сигналов вблизи отверстия в керамике нитрида кремния

An experimental study of the behavior of laser ultrasonic signals near a hole in a plate from dielectric silicon nitride ceramics under the action of external compressive stresses is carried out. A fundamental discrepancy between the results obtained and similar results obtained by us earlier for metals and a quantitative discrepancy with the predicted thermodynamic model of the formation of thermoelastic signals from stressed materials is shown. An explanation of the observed discrepancies is proposed using the model of thermal excitation of lattice defect states that we proposed earlier.

MEMS piezoelectric micro power harvester physical parameter optimization, simulation, and fabrication for extremely low frequency and low vibration level applications

In the last decade, the Piezoelectric Micro Power Harvesters (PMPH) has had a significant attention to produce self-powered small electronic devices at high frequency range. This paper discusses the effects of the PMPH control factor on the PMPH performances including Electric Energy Density and the Normal Electric Field using Taguchi optimization method. Furthermore, the study uses the ANOVA test and the Multivariable linear Regression model to confirm the Taguchi method. Also, it studies the PMPH with optimal control factor simulate through COMSOL Multiphysics 5.4 software. Then, it studies the PMPH first resonance frequency mode with Eigen-Frequency analysis. Moreover, the PMPH performances simulate in time domain through the transient analysis. Therefore, the PMPH is fabricated; it uses silicon substrate coated on both sides with a silicon nitride insulation layer, piezoelectric material is deposited on top of the insulation layer using the RF sputtering technique, the interdigitated gold electrodes (IDEs) are deposited using the DC sputtering, and a proof mass is used to lower the resonance frequency. Furthermore, the fabricated PMPH will be tested with base shaker experiment. Taguchi, ANOVA, and multivariable linear regression analyses results confirm each other. The paper concludes that the piezoelectric material, piezoelectric layer thickness, and silicon membrane thickness are the most three-factors influence the PMPH performances at low vibration levels and extremely low frequency about 1.2 Hz. On the other hand, the piezoelectric layer width and insulator width are the lowest control factors affect the PMPH performances. The PMPH with an optimum parameters simulation results as following, it vibrates at 2.59 Hz with an acceleration magnitude of 0.9 g and the maximum electric energy density of 400 Jm−3. The fabricated PMPH vibrates at the first resonance frequency of 1.2 Hz with acceleration magnitude of 0.9 g. Also, the study finds out that the optimum loading resister of 200 KΩ is found, associated with open-circuit voltage of 18.52 Vp−p. Also, the PMPH produces a maximum electric output power of 135 μW and maximum electric power density of 26.1 mWCm−3. The PMPH Simulation and fabrication results support each other and they demonstrate that the proposed PMPH can work probably at low vibration levels and at extremely low frequency about 1 Hz. Which makes the PMPH suitable for powering small electronic devices, such as cardiac pacemakers and other small medical implants.

Tuning silicon-rich nitride microring resonances with graphene capacitors for high-performance computing applications.

We demonstrate the potential of a graphene capacitor structure on silicon-rich nitride micro-ring resonators for multitasking operations within high performance computing. Capacitor structures formed by two graphene sheets separated by a 10 nm insulating silicon nitride layer are considered. Hybrid integrated photonic structures are then designed to exploit the electro-absorptive operation of the graphene capacitor to tuneably control the transmission and attenuation of different wavelengths of light. By tuning the capacitor length, a shift in the resonant wavelength is produced giving rise to a broadband multilevel photonic volatile memory. The advantages of using silicon-rich nitride as the waveguiding material in place of the more conventional silicon nitride (Si3N4) are shown, with a doubling of the device's operational bandwidth from 31.2 to 62.41 GHz achieved while also allowing a smaller device footprint. A systematic evaluation of the device's performance and energy consumption is presented. A difference in the extinction ratio between the ON and OFF states of 16.5 dB and energy consumptions of <0.3 pJ/bit are obtained. Finally, it has been demonstrated that increasing the permittivity of the insulator layer in the capacitor structure, the energy consumption per bit can be reduced even further. Overall, the resonance tuning enabled by the novel graphene capacitor makes it a key component for future multilevel photonic memories and optical routing in high performance computing.

Helium ion beam induced electron emission from insulating silicon nitride films under charging conditions

Abstract Secondary electron emission from thin silicon nitride films of different thicknesses on silicon excited by helium ions with energies from 15 to 35 keV was investigated in the helium ion microscope. Secondary electron yield measured with Everhart-Thornley detector decreased with the irradiation time because of the charging of insulating films tending to zero or reaching a non-zero value for relatively thick or thin films, respectively. The finiteness of secondary electron yield value, which was found to be proportional to electronic energy losses of the helium ion in silicon substrate, can be explained by the electron emission excited from the substrate by the helium ions. The method of measurement of secondary electron energy distribution from insulators was suggested, and secondary electron energy distribution from silicon nitride was obtained.

Wideband long wave infrared metamaterial absorbers based on silicon nitride

In this paper, we present silicon nitride metamaterial absorber designs that accomplish large bandwidth and high absorption in the long wave infrared (LWIR) region. These designs are based on the metal-insulator-metal topology, insulator (silicon nitride), and the top metal (aluminum) layers are optimized to obtain high absorptance values in large bandwidths, for three different silicon nitride based absorber structures. The absorption spectrum of the final design reaches absorptance values above 90% in the wavelength interval between 8.07 μm and 11.97 μm, and above 80% in the wavelength interval between 7.9 μm and 14 μm, in the case of normal incidence. The difficulty in the design process of such absorbers stems from the highly dispersive behavior of silicon nitride in the LWIR region. On the other hand, silicon nitride is a widely used material in microbolometers, and accomplishing wide band absorption in silicon nitride is crucial in this regard. Therefore, this study will pave the way for more efficient infrared imaging devices, which are crucial for defense and security systems. Additionally, such designs may also find applications in thermal emitters.

Optical, structural and electrical characterizations of stacked Hf-based and silicon nitride dielectrics

High-k stacked dielectric structures were fabricated by a combination of RF magnetron sputtering and plasma-enhanced chemical vapor deposition. Their structural properties were studied versus deposition and annealing conditions by means of attenuated total reflection and high-resolution transmission electron microscopy techniques. All samples demonstrated smoothed surface (with a roughness below 1nm) and abrupt interfaces between the different stacked layers. No crystallization of Hf-based layers was observed after annealing at 800°C for 30min, demonstrating their amorphous nature and phase stability upon annealing. Uniform capacitance–voltage characteristics were measured along the wafers for all stacks. Besides, after round-voltage sweep they demonstrate significant flat-band voltage hysteresis due to charging of the stack caused by carrier injection from the substrate. These phenomena were found to be more pronounced for the stacks with pure HfO2 layers. The stacked structures were implemented for the formation of Ge nanocrystals by means of ion implantation followed by the thermal treatment mentioned above. It was found that the spatial distribution of Ge crystallites in stacked dielectrics affects significantly their electrical properties including the trapping of charge.

Thermopower and hall effect in silicon nitride composites containing thermally reduced graphene and pure graphene nanosheets

Composites consisting of dielectric silicon nitride (Si3N4) with diverse percentages of different graphene nanoreinforcements, such as graphene nanoplatelets (GNP) – 17 and 21vol% – and reduced graphene oxide (rGO) sheets − 4 and 7vol% – displayed thermopower effect. Maximum thermopower was observed for the rGO containing composites, which reached a peak Seebeck coefficient (S) of −26μVK−1 at 300K, whereas GNP composites showed top S of +5μVK−1 at the same temperature. Hall effect measurements indicated that current carriers were different in both composites, electrons for the rGO/Si3N4 (n-type conductor) and holes for the GNP/Si3N4 materials (p-type conductor) and also having ∼1.4 times higher carrier concentration the first composites. The enhanced thermopower of the rGO/Si3N4 composites is attributed to the particular defective nature of rGO sheets, which presented edge defects and nanometer scale defect clusters as shown by the high resolution transmission electron microscope images – probably associated to both oxygen atoms remaining after GO reduction during spark plasma sintering and N doping from the Si3N4 matrix.

The Effect of Interface States on Single-Walled Carbon Nanotube Transistors

Different from p-type single-walled carbon nanotubes (SWCNT) thin film transistors (TFTs) with SiO2 dielectrics, air-stable top-gated n-type SWCNT TFTs are reported with amorphous silicon nitride (SiNx) dielectrics exhibiting the strong dependence of deposition methods and conditions, and metal contacts. Amorphous silicon TFTs-like characteristics was observed from semiconducting single-chirality (6,5) SWCNT TFTs with SiNx deposited at 225°C and appropriate NH3/SiH4 feeding ratio of 10 sccm/5.3 sccm using plasma enhanced chemical vapor deposition (PECVD). These results are interpreted as the effect of interface states between (6,5) SWCNT and SiNx gate dielectrics, which provide the avenue to alter the ratio of free electrons and trapped electrons along applied gate potential.

A three-mask process for fabricating vacuum-sealed capacitive micromachined ultrasonic transducers using anodic bonding.

This paper introduces a simplified fabrication method for vacuum-sealed capacitive micromachined ultrasonic transducer (CMUT) arrays using anodic bonding. Anodic bonding provides the established advantages of wafer-bondingbased CMUT fabrication processes, including process simplicity, control over plate thickness and properties, high fill factor, and ability to implement large vibrating cells. In addition to these, compared with fusion bonding, anodic bonding can be performed at lower processing temperatures, i.e., 350°C as opposed to 1100°C; surface roughness requirement for anodic bonding is more than 10 times more relaxed, i.e., 5-nm rootmean- square (RMS) roughness as opposed to 0.5 nm for fusion bonding; anodic bonding can be performed on smaller contact area and hence improves the fill factor for CMUTs. Although anodic bonding has been previously used for CMUT fabrication, a CMUT with a vacuum cavity could not have been achieved, mainly because gas is trapped inside the cavities during anodic bonding. In the approach we present in this paper, the vacuum cavity is achieved by opening a channel in the plate structure to evacuate the trapped gas and subsequently sealing this channel by conformal silicon nitride deposition in the vacuum environment. The plate structure of the fabricated CMUT consists of the single-crystal silicon device layer of a silicon-on-insulator wafer and a thin silicon nitride insulation layer. The presented fabrication approach employs only three photolithographic steps and combines the advantages of anodic bonding with the advantages of a patterned metal bottom electrode on an insulating substrate, specifically low parasitic series resistance and low parasitic shunt capacitance. In this paper, the developed fabrication scheme is described in detail, including process recipes. The fabricated transducers are characterized using electrical input impedance measurements in air and hydrophone measurements in immersion. A representative design is used to demonstrate immersion operation in conventional, collapse-snapback, and collapse modes. In collapsemode operation, an output pressure of 1.67 MPa pp is shown at 7 MHz on the surface of the transducer for 60-Vpp, 3-cycle sinusoidal excitation at 30-V dc bias.

Advancement of Tooling for Spark Plasma Sintering

A combined experimental and numerical study is conducted to investigate temperature nonhomogeneities within a Spark Plasma Sintering tooling setup. Radial thermal gradients through a powder compact are encountered, a cause of microstructural nonuniformities in sintered specimens, which tend to become more significant when increasing the setup's characteristic size. In the insulating silicon nitride powder compact employed for the experimental procedures, a double pyrometer arrangement detects a strong temperature disparity between the overheated die and the area adjacent to the tooling's axis. A previous finite‐element simulations campaign had individuated a possible solution in a novel punch design, consisting in the drilling of three concentric ring‐shaped holes according to a specific geometrical pattern, whose efficacy is here experimentally verified. Further punch optimization strategies are drawn, involving a refinement of the three‐rings geometry by linearly varying the drilled holes characteristic dimensions along the radial direction, or the selective coating and consequent insulation of the punch cross section with a thin layer of hexagonal boron nitride. Ideal configurations are identified, consisting in a concentration of the graphite punch's mass at its center by means of a tailored holes pattern, or in the coating of a portion of the conventionally shaped punch with boron nitride.

A robust platform cooled by superconducting electronic refrigerators

A biased tunnel junction between a superconductor and a normal metal can cool the latter electrode. Based on a recently developed cooler with high power and superior performance, we have integrated it with a dielectric silicon nitride membrane, and cooled phonons from 305 mK down to 200 mK. Without perforation and covered under a thin alumina layer, the membrane is rigorously transformed into a cooling platform that is robust and versatile for multiple practical purposes. We discussed our results and possibilities to further improve the device.

Graphene Metallization of High-Stress Silicon Nitride Resonators for Electrical Integration

High stress stoichiometric silicon nitride resonators, whose quality factors exceed one million, have shown promise for applications in sensing, signal processing, and optomechanics. Yet, electrical integration of the insulating silicon nitride resonators has been challenging, as depositing even a thin layer of metal degrades the quality factor significantly. In this work, we show that graphene used as a conductive coating for Si3N4 membranes reduces the quality factor by less than 30% on average, which is minimal when compared to the effect of conventional metallization layers such as chromium or aluminum. The electrical integration of Si3N4-Graphene (SiNG) heterostructure resonators is demonstrated with electrical readout and electrostatic tuning of the frequency by up to 0.3% per volt. These studies demonstrate the feasibility of hybrid graphene/nitride mechanical resonators in which the electrical properties of graphene are combined with the superior mechanical performance of silicon nitride.

An electroosmotically-driven micromixer modified for high miniaturized microchannels using surface micromachining

In order to offer the ability of smaller volumes and high throughput in Lab-On-a-Chip and micro Total Analysis Systems devices, more miniaturized components are needed. Due to a low Reynolds number on the microscale, the mixing process can be particularly troublesome. This problem is compounded by the fact that more miniaturization can be challenging in a microfluidic system. In such a case, electroosmotic (EO) force is an efficient force to perturb low Reynolds number fluid. In this paper, a novel Micro-Electro-Mechanical-Systems (MEMS) based fabrication for microfluidic devices, and a more miniaturized micromixer are presented. The proposed technology process requires the covering of excited electrode patterns by a thin Silicon-Nitride (Si3N4) insulator layer. Fabrication parameters such as Low Pressure Chemical Vapor Deposition (LPCVD) Si3N4 deposition effect, and height of the Phosphor Silicate Glass (PSG) sacrificial layer were investigated for the electroosmotically-driven mixer. Particle tracing for fluid flow was illustrated, the particles were stretched and folded for a long time, which was a proof of chaotic regime. Finite Element Analysis (FEA) revealed that the mixer with covered electrodes provides the high mixing efficiency of above 90% for a 96 μm long microchannel. Using a silicon nitride insulator layer reduces high electric field gradient at sharp corners and edges of the electrodes, leading to the elimination of unwanted electrolyte effects. Thus, the excitation and geometrical parameters were optimized for the micromixer.

Plasmonic Antennas Hybridized with Dielectric Waveguides

For the purpose of using plasmonics in an integrated scheme where single emitters can be probed efficiently, we experimentally and theoretically study the scattering properties of single nanorod gold antennas as well as antenna arrays placed on one-dimensional dielectric silicon nitride waveguides. Using real space and Fourier microscopy correlated with waveguide transmission measurements, we quantify the spectral properties, absolute strength, and directivity of scattering. The scattering processes can be well understood in the framework of the physics of dipolar objects placed on a planar layered environment with a waveguiding layer. We use the single plasmonic structures on top of the waveguide as dipolar building blocks for new types of antennas where the waveguide enhances the coupling between antenna elements. We report on waveguide hybridized Yagi-Uda antennas which show directionality in out-coupling of guided modes as well as directionality for in-coupling into the waveguide of localized excitations positioned at the feed element. These measurements together with simulations demonstrate that this system is ideal as a platform for plasmon quantum optics schemes as well as for fluorescence lab-on-chip applications.

Experimental Evaluation of the Light Trapping Potential of Optical Nanostructures for Thin-Film Silicon Solar Cells

We describe a method based on nanoimprinting and non-absorbing insulating silicon nitride electrodes for evaluating the light trapping potential of photonic nanostructures for thin-film silicon solar cells. We validate our method by relating the optical reflectance of the full solar cell stack to the external quantum efficiency of functional cells. Our method provides a useful experimental tool to compare different nanostructures circumventing complications arising from parasitic absorption and electrical cell performance.