Planar Capacitor Research Articles

Flow patterns and heat transfer in a dielectric liquid inside a planar capacitor under microgravity conditions

Heat transfer in a planar capacitor containing a dielectric liquid subject to an increasing high-frequency voltage and a fixed temperature gradient under microgravity is investigated using direct numerical simulations. When the intensity of the applied voltage exceeds a critical value, the dielectrophoretic force induces thermoelectric convection in the form of stationary vortices. The increase in the voltage leads to different types of convective patterns and to the increase in the heat transfer coefficient between the electrodes of the capacitor.

Smaller than MLCC: CCW (Ceramic Capacitor Wire)

The world’s smallest discrete capacitor was invented in a cylindrical form factor for high-frequency power delivery, contrary to a planar capacitor such as MLCC. A dielectric layer of Al2O3 (5~50nm ALD) was deposited on conventional Au metal wires (18~40µm), and subsequently, a 2nd electrode metal (0.5~1µm) was sputtered on the Al2O3 layer. Advanced wire bonding was used to assemble CCW to PCB pads for electrical connections required capacitors. Electrical simulations were used to characterize CCW in terms of electrical performances. The capacitance measurements were compared between CCW & MLCC in conjunction with electrical simulation at high frequencies for RF & HPC applications. CCW can also be embedded into PCB and integrated into package chips.

Advances in a Microwave Sensor-Type Interdigital Capacitor with a Hexagonal Complementary Split-Ring Resonator for Glucose Level Measurement

This study involved the creation and assessment of a microwave sensor to measure glucose levels in aqueous solutions without invasiveness. The sensor design utilized a planar interdigital capacitor (IDC) loaded with a hexagonal complementary split-ring resonator (HCSRR). The HCSRR was chosen for its ability to generate a highly intense electric field that is capable of detecting variations in the dielectric characteristics of the specimen. A chamber tube was used to fill glucose solutions at the sensor’s sensitive area, and changes in the device’s resonance frequency (Fr) and reflection coefficient (S11) were used to measure glucose levels. Fitting formulas were developed to analyze the data, and laboratory tests showed that the sensor could accurately measure glucose levels within a range of 0–150 mg/dL. At a concentration of 37.5 mg/dL, the sensitivity based on S11 and Fr reached maximum values of 10.023 dB per mg/dL and 1.73 MHz per mg/dL, respectively. This implies that the sensor put forward has the possibility of being utilized in medical settings for the monitoring of glucose levels.

Enhancing the performance and mechanical stability of 2D-based hybrid micro-supercapacitors using dendritic-gold as framework layer

In recent years scaling-down approaches on supercapacitors has led to the definition of Micro-Supercapacitors (μSC). The demand for these devices is increasing for many applications in microelectronics, such as wearable energy storage and self-powered sensors. Recently, many efforts have been made to achieve good results in terms of power and energy densities. However, the current research challenge is to develop a sustainable chain production, involving eco-friendly materials, such as water-based electrolytes, organic binders and low-impact active material. This work presents a hybrid μSC using low impact materials and a fully water-based solution. Different approaches were adopted for patterning the current collectors and for the deposition of the active materials. The material chosen as anode was MnO2 deposited by electroplating, which presents pseudocapacitive behavior. The active material used for the cathode was Activated Carbon (AC), deposited by drop-casting, which works through the electric double layer (EDL) capacitance effect. The electrolyte was 1 M Na2SO4 in water. We investigated the addition of an interlayer micro-structure made of Dendritic-Gold (D-Gold). The results show that such a layer seems to have positive effects in terms of wettability and mechanical stability, enhancing the adhesion of the active material. Electron microscopy measurement shows the characteristic tree-like shape of the layer. The device reports a capacitance of about 14 to 23 mF cm-2 and a large voltage window equal to 1.6 V. The present research explores, for the first time, the effects of dendritic gold in planar electrochemical capacitors. The findings should give an important contribution for boost energy storage densities in the field of 2D micro-supercapacitors.

Area-Selective Deposition of AlOx and Al-Silicate for Fully Self-Aligned Via Integration

The rush for better-performing electronics, and manufacturing processes that heavily rely on "top-down" patterning techniques, is making the integration of "self-aligned" fabrication methods, such as area-selective deposition (ASD), a critical objective for continued device scaling. The fully self-aligned via (FSAV) scheme is broadly proposed as a "killer application" to determine whether ASD can shift from an R&D process to high-volume manufacturing. Nevertheless, the lack of a suitable low-κ deposition process has prevented the realization of FSAV by dielectric-on-dielectric ASD. This is primarily due to the high temperature and/or strong oxidizers employed during low-κ dielectric deposition and their unsuitability in the presence of organic masks, such as self-assembled monolayers (SAMs), used to prevent material nucleation during ASD. In this work, AlOx and Al-silicate atomic layer deposition (ALD) processes are studied to provide suitable materials for ASD-enabled FSAV. Dimethylaluminum isopropoxide and H2O are utilized to deposit the metal oxide, whereas Al-silicate is grown by adding 2,2-dimethoxy-1,6-diaza-2-silacyclooctane (DMDAcO) pulses to the AlOx ALD cycle. The selectivity of such processes is demonstrated on 50 nm Cu/SiO2 structures, using octadecanethiol-derived SAMs to inhibit material nucleation on the metal lines. Scanning and transmission electron microscopies are employed to assess the quality of the ASD processes and investigate the mechanisms behind defect generation on a nongrowth surface. X-ray photoelectron spectroscopy measurements show the high purity of the AlOx film, whereas DMDAcO-ligand incorporation into the Al-silicate matrix is observed. Planar capacitor structures are used to assess the electrical properties of both ASD films, revealing that the silicate film exhibits a relatively low κ-value (5.3 ± 0.2), with a high acceleration field factor (32.4 ± 1.4) and a dielectric breakdown voltage of 6.0 ± 0.3 V at 100 °C.

Packaged Flexible Planar Copper Foil Fractional-Order ‘0.61–0.87’ Capacitors: Series/Parallel Combinations

The fabrication of packaged, flexible, and planar fractional-order capacitors (FOCs) using copper foil electrodes and thin films of PVDF polymer nanocomposite dielectric is presented in this paper. An extensive comparison of FOC properties is made by using two separate conductive fillers, i.e., graphene nanosheets (GNS) and reduced graphene oxide (rGO). Similar fractional-order is observed at a particular filler loading in both types of FOCs; however, differences in the pseudocapacitance values and width of the constant phase (CP) zone exists. Fractional order α (alpha) is reported to vary in the range 0.61–0.87 in impedance measurements made on individual samples of rGO/PVDF and GNS/PVDF FOCs and series/parallel connections of two identical-order FOCs. For series/parallel connection of arbitrary-order FOCs, α varies from 0.61 to 0.83. Phase angle variation ranges from − 56.2° to − 79° for standalone pure FOC samples, whereas, for series/parallel connection of identical or arbitrary order FOCs, phase ranges from − 54.94° to − 77.75°. Phase ripple varies between ± 1.1° and ± 4.8°, and a maximum CP zone of 4 decades (1 kHz to 10 MHz) for the fabricated samples is reported. Industrial manufacturing of large-value capacitors demands materials to be flexible to enable rolling of large-area electrodes into a miniature device. FOCs fabricated in this work match the design specifications of commercial standard thin film capacitors and show high-value capacitances as well as flexibility of materials and structure.

Effects of post metallization annealing on Al2O3 atomic layer deposition on n-GaN

The chemical, physical and electrical properties and the robustness of post metallization annealed Al2O3 atomic layers deposited on n-type GaN are investigated in this work. Planar metal insulator capacitors are used to demonstrate a gate-first with following ohmic contacts formation at elevated temperature up to 600 °C process flow. X-ray photoelectron spectroscopy indicates that no new bonds in the Al2O3 layer are formed due to exposure to the elevated annealing temperature. X-ray diffraction measurements show no crystallization of the oxide layer. Atomic force microscopy shows signs of degradation of the sample annealed at 600 °C. Electrical measurements indicate that the elevated annealing temperature results in an increase of the oxide depletion and the deep depletion capacitances simultaneously, that results in a reduction of the flat band voltage to zero, which is explained by fixed oxide charges curing. A forward bias step stress capacitance measurement shows that the total number of induced trapped charges are not strongly affected by the elevated annealing temperatures. Interface trap density of states analysis shows the lowest trapping concentration for the capacitor annealed at 500 °C. Above this temperature, the interface trap density of states increases. When all results are taken into consideration, we have found that the process thermal budget allows for an overlap between the gate oxide post metallization annealing and the ohmic contact formation at 500 °C.

An Ex Vivo Study of Wireless Linkage Distance between Implantable LC Resonance Sensor and External Readout Coil.

The wireless monitoring of key physiological parameters such as heart rate, respiratory rate, temperature, and pressure can aid in preventive healthcare, early diagnosis, and patient-tailored treatment. In wireless implantable sensors, the distance between the sensor and the reader device is prone to be influenced by the operating frequency, as well as by the medium between the sensor and the reader. This manuscript presents an ex vivo investigation of the wireless linkage between an implantable sensor and an external reader for medical applications. The sensor was designed and fabricated using a cost-effective and accessible fabrication process. The sensor is composed of a circular planar inductor (L) and a circular planar capacitor (C) to form an inductor-capacitor (LC) resonance tank circuit. The reader system comprises a readout coil and data acquisition instrumentation. To investigate the effect of biological medium on wireless linkage, the readout distance between the sensor and the readout coil was examined independently for porcine and ovine tissues. In the bench model, to mimic the bio-environment for the investigation, skin, muscle, and fat tissues were used. The relative magnitude of the reflection coefficient (S11) at the readout coil was used as a metric to benchmark wireless linkage. A readable linkage signal was observed on the readout coil when the sensor was held up to 2.5 cm under layers of skin, muscle, and fat tissue. To increase the remote readout distance of the LC sensor, the effect of the repeater coil was also investigated. The experimental results showed that the magnitude of the reflection coefficient signal was increased 3-3.5 times in the presence of the repeater coil, thereby increasing the signal-to-noise ratio of the detected signal. Therefore, the repeater coil between the sensor and the readout coil allows a larger sensing range for a variety of applications in implanted or sealed fields.

Gate Oxide Reliability and V<sub>TH</sub> Stability of Planar SiC MOS Technology

Similar charge to failure distributions with mean values of about 50 C/cm2 were measured for planar SiC MOSFETs and MOS capacitors. Fast occurring and saturating negative flatband and threshold voltage drops were found in time resolved 1 second long pulsed gate current stress with IG=1 mA/cm2 at T=150 °C. No substantial difference in VTH drift rate with VGS=28 V at T=150 °C was found after about 10 s recovery period for IG stressed devices compared with unstressed devices. Additionally, IG stressed and unstressed devices did not differ in final VTH shift at T=25 °C after VGS=28 V stress (during 3 hrs or 31 hrs). More gate oxide reliability characterization is important to determine if 1 mA/cm2 pulsed gate current stress creates any permanent changes to the SiC MOSFET device behaviour. Additionally, parametric shifts in VTH and RDSon was examined after long-term AC gate bias stress by a gate driver switching between-8V and 20V for four different commercially available SiC MOSFETs.

INVESTIGATION OF VOLT-FARAD CHARACTERISTICS OF THIN MULTIFERRROIC FILMS

In this work, the influence of the concentration of manganese ions in BST films on the capacitance-voltage characteristics (CV characteristics, I–V characteristics, tgδ) of the Cu-Cr/BST/α-Al2O3 and Cu-Cr/BST/GGG structures was studied. To measure the electrophysical characteristics, multiferroic thin-film the samples were made in the form of planar capacitors. Measurements of the electrical properties of the formed planar structures were carried out at a frequency of 1 MHz.

Study and characterization of GaN MOS capacitors: Planar vs trench topographies

Developing high quality GaN/dielectric interfaces is a fundamental step for manufacturing GaN vertical power transistors. In this paper, we quantitatively investigate the effect of planar etching treatment and trench formation on the performance of GaN-based MOS (metal oxide semiconductor) stacks. The results demonstrate that (i) blanket etching the GaN surface does not degrade the robustness of the deposited dielectric layer; (ii) the addition of the trench etch, while improving reproducibility, results in a decrease in the breakdown performance compared to the planar structures. (iii) For trench structures, the voltage for a 10 year lifetime is still above 20 V, indicating a good robustness. (iv) To review the trapping performance across the metal-dielectric-GaN stack, forward-reverse capacitance–voltage measurements with and without stress and photo-assistance are performed. Overall, as-grown planar capacitors devoid of prior etching steps show the lowest trapping, while trench capacitors have higher interface trapping and bulk trapping comparable to the blanket etched capacitors. (v) The nanostructure of the GaN/dielectric interface was characterized by high resolution scanning transmission electron microscopy. An increased roughness of 2–3 monolayers at the GaN surface was observed after blanket etching, which was correlated with the higher density of interface traps. The results presented in this paper give fundamental insight on how the etch and trench processing affects the trapping and robustness of trench-gate GaN-metal-oxide-semiconductor field effect transistors and provide guidance for the optimization of device performance.

Physical Modeling of Monolithic Self-Rolled-Up Microtube Interdigital Capacitors

This article presents a physical model for monolithic self-rolled-up microtube interdigital capacitors and elaborates their working mechanisms in comparison to on-chip planar interdigital capacitors. Besides the high-frequency phenomena such as the skin effect in thin, wide metal films, the model accounts for the complexities resulting from all possible 3-D electrode configurations, such as the inner diameter-dependent overlapping capacitances and edge capacitances between electrodes, as well as parasitic inductances within the rolled-up structure between the fingers, for integer and noninteger number of turns. The model is validated by the measured results of fabricated self-rolled-up membrane (S-RuM) interdigital capacitors over a wide range of layout and process parameters. This fully enables the structural design optimization for electrical performance of this 3-D device architecture.

Influence of shielding on the dependence of capacitance of planar capacitor on a distance of a measured object

This article deals with the topic of the shielding effect of electrodes in the design of capacitance sensors. The main focus of the article is the phenomenon, which occurs when placing shielding electrodes between planar capacitor electrodes. This phenomenon naturally occurs when the multi-electrode setup is being used. Such setup is used in electronic capacitance tomography (ECT). The first part of the article briefly describes the theoretical attributes of a planar capacitor. Then the model of the multi-electrode system is explained. Subsequently, the experiment during which the phenomenon was observed, is being described. The real measurement is then compared to the simulation of the equal setup. Results, implications, and possible explanations are being discussed in the conclusion.

Electrophoretic deposition and capacitive characteristics of composite electrode materials based on CNTs and ruthenium oxide for planar supercapacitors

In this work, a method for the formation of planar supercapacitors, which combines electrophoretic deposition of composite electrode materials based on CNTs and ruthenium oxide, and laser engraving, is proposed. The features of electrophoretic deposition are considered and the influence of the main technological modes on the morphology and composition of the formed layers of electrode materials is determined. The conducted studies of the electrophysical characteristics of the formed samples confirmed the possibility of producing planar capacitors with a high capacity and their potential applicability for a number of applications in microelectronics.

Design and Performance of Additively Manufactured In-Circuit Board Planar Capacitors

This article discusses the design and performance of planar capacitors built as pairs of conductive plates by additive manufacturing as part of an electronic circuit board. This article covers several geometries and layers of parallel plates that allow for different capacitance values, from a few picofarads (pF) to several nanofarads (nF). The dc, ac, and radio frequency (RF) characterization demonstrated superior performance compared to off-the-shelve surface mount device (SMD) capacitors up to 20 GHz. The additively manufactured capacitors exhibit breakdown voltages in excess of 1 kV and subpicoampere leakage currents, while the change in RF impedance changes, as a function of frequency, is a factor of $3\times $ smaller than SMD capacitors.

Enhanced Tunability of BaTixSn1−xO3 Films on Dielectric Substrate

The structural properties of ferroelectric films of barium titanate-stannate on alumina substrates and the microwave characteristics of planar capacitive elements based on them are studied. It is established that the composition of the gas medium and the temperature of the substrate during the deposition of the film has a significant effect on the crystal structure, phase composition of the films and their electrical characteristics. Planar capacitors based on films subjected to high-temperature annealing after deposition exhibit 85% tunability at a frequency of 2 GHz, which is the best result for today.

Pyroelectric Properties of BaxSr(1-x)TiO3/PVDF-TrFE Coating on Silicon.

Bilayer coatings of barium strontium titanate (BaxSr(1−x)TiO3)/poly [(vinylidenefluoride-co-trifluoroethylene] (PVDF-TrFE) were integrated on silicon Si (100) for pyroelectric devices. Pyroelectric properties of the composite were determined for different electrode materials (silver and aluminum) and different electrodes configurations creating an electric field in parallel and in-plane direction in the ferroelectric coating. For this purpose, parallel-plate and planar interdigital capacitors were fabricated. Anisotropy in the pyroelectric response was noted for the different directions of the measured electrical potential. The dynamic method was used to evaluate the pyroelectric properties in the temperature range of 22 to 48 °C. Pyroelectric response with a higher value was observed at the one plate’s configuration of interdigital electrodes. The voltage response was the strongest when silver contacts were used. At temperatures near room temperature, the voltage increased by 182 µV at resolution of 7 µV/°C for the in-plain device configuration, vs. 290 µV at a resolution of 11 µV/°C for the out-of-plain configuration. A relationship between the surface morphology of the ferroelectric oxide and oxide/polymer coating and the pyroelectric voltage was also found, proving the smoothening effect of the introduction of polymer PVDF-TrFE over the BaSrTiO3 grains.

Theory of Transport in Ferroelectric Capacitors.

The spontaneous order of electric and magnetic dipoles in ferroelectrics and ferromagnets even at high temperatures is both fascinating and useful. Transport of magnetism in the form of spin currents is vigorously studied in spintronics, but the polarization current of the ferroelectric order has escaped attention. We therefore present a time-dependent diffusion theory for heat and polarization transport in a planar ferroelectric capacitor with parameters derived from a one-dimensional phonon model. We predict steady-state Seebeck and transient Peltier effects that await experimental discovery.

비아를 이용한 CRLH 전송선로 안테나 소형화

In this study, miniaturization of composite right-left handed (CRLH) transmission line (TL) antennas using via structure is proposed. The proposed CRLH TL antenna replaces the planar interdigital capacitor structure of the conventional CRLH TL antenna using vias in the printed circuit board multilayer structure. Via structure derives series capacitance values by replacing the finger-shaped patterned parts that comprise the conventional interdigital capacitor. The proposed model reduces the increased length of 8.34 mm to 2.66 mm for every one-cell increase based on an operating frequency of 2.9 GHz. Unlike the three-cell conventional model that utilizes 5.17 dBi at a size of 47.79 mm, the proposed four-cell model utilizes 5.35 dBi at a size of 33.41 mm.

Wireless Microfluidic Sensor for Metal Ion Detection in Water

In the present work, a wireless microfluidic sensor based on low-temperature cofired ceramic (LTCC) technology for real-time detection of metal ions in water is proposed. The wireless sensor is composed of a planar spiral inductor and parallel plate capacitor (LC) resonant antenna, which integrates with the microchannel in the LTCC substrate between the capacitor plates. Aqueous solutions of Pb(NO3)2, Cd(NO3)2, Mg(NO3)2, Ca(NO3)2, NaNO3, and KNO3 with concentrations of 0–100 mM were tested with the sensors. The metal ion and its concentration in water can be tested by the amplitude of the reflection coefficient (S11) and the resonance frequency (fr) of the wireless microfluidic sensor. The metal ion species can be distinguished from the wireless response behavior of the sensor. The detection limit of the sensor for the selected metal ionic solutions could reach as low as 5 μM. The normalized sensitivity of the sensor is 0.47%, which is higher than that of the reported liquid microfluidic sensors based on microwave resonators. The wireless microfluidic sensor of this study is promising for rapid and convenient detection of heavy metal ion pollutants in the industrial wastewater.