Alternative Dielectric Materials Research Articles

Electrostatic Correlations Lead to High Capacitance in Zwitterion-Containing Thin Films.

A novel zwitterion composed of an imidazolium tethered to an anionic sulfonyl(trifluoromethane sulfonyl)imide group was prepared as an alternative dielectric material to traditional ionic liquids. The zwitterion not only melted below 100 °C but also proved to be nonhygroscopic. High-capacitance organic dielectric materials were obtained by blending this compound with poly(methyl methacrylate) over a range of concentrations and thicknesses. Above a specific temperature and concentration, films exhibit a capacitance nearly equivalent to that of an electrostatic double layer, approximately 10 μF/cm2, regardless of their thickness. Grazing-incidence wide-angle X-ray scattering experiments suggest that the zwitterions adopt a lamellar ordering at their surface above a critical concentration. The observed ordering is correlated with a 1000-fold increase in capacitance. The behavior suggests that the zwitterions exhibit strong electrostatic correlations throughout the film bulk, pointing the way toward a novel class of organic dielectric materials.

Technology of High-k/Metal-Gate Stack

Abstract The High-k/Metal-Gate Stack (HKMG) technology represents a seminal advancement in semiconductor fabrication, predicated upon the substitution of SiO2 with high-k dielectric materials, coupled with the integration of metal gate materials. This technological paradigm shift has emerged as a transformative response to the intricate challenges encountered within the semiconductor industry, a sector perpetually engaged in the relentless pursuit of diminishing the critical dimensions of semiconductor devices. Issues such as increased power leakage, enhanced parasitic capacitance, and the escalating complexity of gate insulators have impeded the sustainable downscaling of traditional silicon dioxide-based devices. These challenges have necessitated a comprehensive re-evaluation of the materials and processes involved in semiconductor manufacturing, leading to the conception and evolution of the HKMG technology. This article’s analysis of the developmental trajectory of HKMG technology reveals a progression marked by the systematic exploration of alternative high-k dielectric materials, rigorous compatibility assessments with metal gate materials, and the concurrent refinement of manufacturing processes to ensure seamless integration. After that, elucidating the impediments encountered during its evolution and expounding upon the corresponding ameliorative measures instituted. Looking ahead, ongoing research focusing on the synthesis of advanced high-k dielectric materials, and the development of novel metal gate materials with superior compatibility to further enhance device performance and functionality makes HKMG technology a huge prospect. Such advancements are paving the way for the realization of more powerful, energy-efficient, and compact electronic devices.

A Green High-k Dielectric from Modified Carboxymethyl Cellulose-Based with Dextrin.

Many crucial components inside electronic devices are made from non-renewable, non-biodegradable, and potentially toxic materials, leading to environmental damage. Finding alternative green dielectric materials is mandatory to align with global sustainable goals. Carboxymethyl cellulose (CMC) is a bio-polymer derived from cellulose and has outstanding properties. Herein, citric acid, dextrin, and CMC based hydrogels are prepared, which are biocompatible and biodegradable and exhibit rubber-like mechanical properties, with Young modulus values of 0.89 MPa. Hence, thin film CMC-based hydrogel is explored as a suitable green high-k dielectric candidate for operation at low voltages, demonstrating a high dielectric constant of up to 78. These fabricated transistors reveal stable high capacitance (2090 nF cm-2) for ≈±3V operation. Using a polyelectrolyte-type approach and poly-(2-vinyl anthracene) (PVAn) surface modification, this study demonstrates a thin dielectric layer (d ≈30 nm) with a small voltage threshold (Vth ≈-0.8 V), moderate transconductance (gm ≈65 nS), and high ON-OFF ratio (≈105). Furthermore, the dielectric layer exhibits stable performance under bias stress of ± 3.5 V and 100 cycles of switching tests. The modified CMC-based hydrogel demonstrates desirable performance as a green dielectric for low-voltage operation, further highlighting its biocompatibility.

Exploration of structural and dielectric properties of orthorhombic Ta2O5 nanoplatelets towards the potential optoelectronic devices

The dielectric characteristics of tantalum pentoxide (Ta2O5) nanostructures, synthesized by hydrothermal process, have been investigated in the temperature range of 80 K to 400 K and frequency range of 20 Hz to 2 MHz. X-ray diffraction (XRD) confirms the formation of highly crystalline and orthorhombic phase of the nanostructures sintered at 950 ºC. The electron microscope images reveal that the synthesized nanostructures change their morphology to nanoplatelets upon increasing the sintering temperature. Further, UV–visible absorbance, FTIR and Raman spectra of the synthesized nanostructures were obtained to investigate their optical properties. The experimentally obtained dielectric results indicate that both the dielectric constant (ε) and dielectric loss (D) values increase with increasing operating temperature. Also, the dielectric constant increases to 20 while the dielectric loss decreases to <0.025 at room temperature on increasing the sintering temperature. At 300 K and 1 kHz, the value of ε becomes almost twice that of as-synthesized nanostructures i.e. from 10 to 20 on increasing the sintering temperature to 950 ºC. The enhancement in dielectric constant can be justified by the thermally activated orientational and interfacial polarization associated with the increase in the grain size of the Ta2O5 nanoplatelets at higher sintering temperatures. Furthermore, the frequency dependence of ε indicates the high effect of the distribution of relaxation time in the Ta2O5 nanoplatelets at lower frequencies. Overall, this study provides a better understanding of the structural and dielectric behaviour of Ta2O5 nanostructures in correlation with varying sintering temperature. The results suggest that the orthorhombic Ta2O5 nanoplatelets have potential applications as alternative dielectric materials in various electronic and optoelectronic devices.

NS-GAAFET Compact Modeling: Technological Challenges in Sub-3-nm Circuit Performance

NanoSheet-Gate-All-Around-FETs (NS-GAAFETs) are commonly recognized as the future technology to push the digital node scaling into the sub-3 nm range. NS-GAAFETs are expected to replace FinFETs in a few years, as they provide highly electrostatic gate control thanks to the GAA structure, with four sides of the NS channel entirely enveloped by the gate. At the same time, the NS rectangular cross-section is demonstrated to be effective in its driving strength thanks to its high saturation current, tunable through the NS width used as a design parameter. In this work, we develop a NS-GAAFET compact model and we use it to link peculiar single-device parameters to digital circuit performance. In particular, we use the well-known BSIM-CMG core solver for multigate transistors as a starting point and develop an ad hoc resistive and capacitive network to model the NS-GAAFET geometrical and physical structure. Then, we employ the developed model to design and optimize a digital inverter and a five-stage ring oscillator, which we use as a performance benchmark for the NS-GAAFET technology. Through Cadence Virtuoso SPICE simulations, we investigate the digital NS-GAAFET performance for both high-performance and low-power nodes, according to the average future node present in the International Roadmap for Devices and Systems. We focus our analysis on the main different technological parameters with regard to FinFET, i.e., the inner and outer spacers. Our results highlight that in future technological nodes, the choice of alternative low-K dielectric materials for the NS spacers will assume increasing importance, being as relevant, or even more relevant, than photolithographic alignment and resolution at the sub-nm scale.

Theoretical investigation of Bragg Reflector optical sensor for the measurement of cryogenic temperature

The goal of the proposed work is to design and analyze a low temperature sensor to measure cryogenic temperature in the range of 0–120 K. Proposed sensor design uses Distributed Bragg Reflector (DBR) multi-layer structure. DBR consists of high-low alternate dielectric materials arranged in one direction which acts as a one-dimensional photonic crystal (pc). Gallium Arsenide (GaAs) is used as high dielectric material and air as low dielectric material. GaAs dielectric constant is a function of the temperature and hence it can be used to detect any variation in the temperature. In this work, the number of alternate multi-layers (N) is chosen as 8 and the frequency of input electromagnetic wave is taken as 24THz. We achieved a high sensitivity of 1.525 nm/K with a Q factor of 3534. The proposed sensor suits for the applications where critical low temperature measurement is needed.

High‐Sensitivity Tunable Bloch Surface Waves’ Biosensor Using Nanocomposite Cap Layer

The advantage of the high versatility of the nanocomposite (Nc) materials in modeling photonic structure devices is exploited to design an optical biosensor based on Bloch surface waves (BSWs) to probe different biomolecular species. The suggested biosensor is constituted by two periods of low and high refractive indices (RIs) of alternate dielectric materials SiO2 and TiO2 capped by Ag−TiO2 Nc layer operating under the Kretschmann configuration and using p‐polarized incident light. Herein, the biosensor performances are theoretically investigated in a wide range of the sensing medium RI [1.33, 1.61] using selected operating wavelengths 455, 465, 480, 500, and 600 nm to deviate a large dielectric loss of the Ag−TiO2 Nc layer. The results show that the structure sustains BSW for each wavelength in separate domains of the sensing medium RI conferring to the proposed biosensor a potential for the high‐sensitive multiwavelength detection of different biomolecular entities.

Bio-dielectric based on superconductors yttrium calcium barium copper oxide (YCaBa2Cu3O7−x ) from eggshell as calcium oxide source via sol-gel process

Abstract Eggshell is a rich source of calcium that is a dielectric material used for doping in a superconductor. Yttrium calcium barium copper oxide (Y x Ca1−x Ba2Cu3O7) was prepared using the sol-gel process and fired at 900 °C or 1,000 °C. The stoichiometric ratio of the raw materials Y2O3:BaCl2:CuO:CaO was 1:2:3:1 based on the molar mass. The obtained YCaBCO had an orthorhombic crystal structure composed of distorted oxygen-deficient perovskite. The orthorhombic structure was unsymmetrical, providing a substantial increase in the physical electromagnetic properties of the superconductor. The YBCO-900-reference analyzed using an impedance analyzer in the range from 500 Hz to (1 × 106) Hz and at room temperature (27 °C) had the following values for capacitance, electrical conductivity, and dielectric constant ± standard error: 8,286.70 ± 28.49 pF, (3.60 ± 0.01) × 107 S/m, and 1,874.794 ± 6.446, respectively. The YCaBCO-900-eggshell (Y x Ca1−x Ba2Cu3O7) analyzed at 500 Hz at room temperature (27 °C) had high values for capacitance, electrical conductivity, and dielectric constant, namely, 8,540.10 ± 2.00 pF, (1.32 ± 0.00) × 108 S/m, and 1,988.540 ± 0.500, respectively. Furthermore, the YCaBCO-900-eggshell had electrical properties (capacitance, conductivity, and dielectric constant values) higher than those of YCaBCO-900-commercial grade measured under the same conditions. The YCaBCO-900-com grade had capacitance of 8,225.75 ± 0.73 pF, electrical conductivity of (1.40 ± 0.01) × 108 S/m, and dielectric constant of 1,874.59 ± 0.17, respectively. Therefore, eggshell is an alternative dielectric material useful for doping in yttrium barium copper oxide (YBCO) to form YCaBCO, thus causing an increase in its electrical properties. The obtained superconductor is a candidate that could be applied in many industries.

Enhanced dielectric properties of La-doped 0.75BaTiO3-0.25Bi(Mg0.5Ti0.5)O3 ceramics for X9R-MLCC application

A series of 0.75Ba(1−x)La2x/3TiO3-0.25Bi(Mg0.5Ti0.5)O3 (x = 0–0.2) ceramics have been synthesized by doping La2O3 into 0.75BaTiO3-0.25Bi(Mg0.5Ti0.5)O3 (0.75BT-0.25BMT), and their structure and dielectric properties investigated. Upon characterizing the structural properties, the single-phase perovskite structure is identified for all the samples and the long-range order of 0.75BT-0.25BMT is verified to be further destroyed with the addition of La2O3. Moreover, it is found that the density of 0.75BT-0.25BMT can be improved by doping with La2O3, which also promotes the grain growth. Regarding the dielectric properties, the peak shifting effect induced by La3+ improves the permittivity-temperature stability of 0.75BT-0.25BMT remarkably by strengthening its relaxation behavior. Among all the samples, 0.75Ba0.8La0.4/3TiO3-0.25Bi(Mg0.5Ti0.5)O3 shows the most outstanding permittivity-temperature stability with εr = 572 ± 15% (compared with εr at 25 °C) over the temperature range −70°C–238 °C at 1 kHz, which is notably better than that of 0.75BT-0.25BMT (−4°C–58 °C) and satisfies the specification of the X9R multilayer ceramic capacitor (MLCC). Our work provides one promising option for selecting an alternative dielectric material in terms of permittivity-temperature stability, which advances the development of the X9R MLCC.

Simulation and investigations on semiconductor materials and devices with surround gate geometry for high performance and low power nano scale applications

All The device with surround gate geometry provides a better way to scale down the dimensions and optimization of power and performance for nano scale applications. The superior gate control can be obtained by novel materials and innovative techniques for various regions of the nano scale device. The surround gate (SG) field effect transistor provides high gain, high trans-conductance, reduced short channel effects and conditions for scaling the technology to sub nano scale. The device has been modeled using SILCAVO Atlas3d and DevEdit3D module also used for creating the device structure with integration of multiple layers of different materials. In this paper surround gate device input (ID-VGS) and output (ID-VDS) characteristics have been intensively studied and parameters including ION/IOFF ratio, DIBL, sub threshold slope extracted and compared with the conventional devices. The silicon nanowire field effect transistor (SiNWFET) with surround gate geometry at 0.6 V applied between source and drain exhibits threshold voltage (VTH) 0.204 V, drain induced barrier lowering (DIBL) 172 mV/V, sub-threshold swing (SS) 104.23 mV/dec, ION=440.1μA, IOFF=1.04 μA and ION/IOFF ratio 4.24e+02. The results demonstrate improvement in device parameters for the SiNWFET device as compared to other conventional MOSFETs. The result obtained for SiNWFET are also compared with FinFET and CNTFET devices. This research also investigates the integration of alternate channel, dielectric and gate materials into novel GAA device structure.

Coconut shell, coconut shell activated carbon and beta-silicon carbide reinforced polymer composite: An alternative dielectric material for wireless communication application

The effect of coconut shell (CS), coconut shell activated carbon (CSAC) and beta-silicon carbide (β-SiC) in polymer composites was investigated. Elemental composition, surface morphologies and structural analyses of the fillers were performed using carbon, hydrogen, nitrogen and sulfur (CHNS) analyser, scanning electron microscope (SEM) and X-ray Diffractometer (XRD). The dielectric properties of the composites were measured using open-ended coaxial line method. CS and CSAC fillers had positive influence on the dielectric properties (ε’, ε” and σ) of the polymer composites, contributed by the orientation polarizations arises from polar nature of the amorphous CS and CSAC fillers. β-SiC filler had insignificant influence on the dielectric properties of the polymer composites due to its single polarization of the crystalline structure filler. This finding is in agreement with XRD patterns of CS and CSAC fillers that revealed the presence of amorphous structure with broad diffraction peaks that were detected at 2ϴ=22.236°, 34.8604° and 2ϴ=23.985° and 44.015°, respectively. The amorphization structure in the polymer composites allows the displacement and conduction currents that were induced from electric field to flow through the polymer composites when subjected to electromagnetic energy, thus increased the dielectric properties of the composites.

Impedance spectroscopy study of electrical properties of polymer blend interlayered Al/PEG-PVA/p-Si (MPS) structure

PEG-PVA polymer blend has been prepared by solution processing and a thin film of the blend has been spin coated as an interfacial layer on a p-Si wafer. Capacitance-voltage (C–V) and conductance-voltage (G/ω-V) characteristics of Al/PEG-PVA/p-Si (metal-polymer-semiconductor) structure were studied in a frequency range of 5 KHz to 1 MHz with voltage bias swept from −4 V to +5 V, by considering interface states density (Dit) and series resistance (Rs) at room temperature. The voltage and frequency dependent profile of Dit were evaluated from the low-high frequency capacitance (CLF-CHF) and Hill-Coleman methods. The Rs profiles for various frequencies and voltages were evaluated using Nicollian-Brews admittance method. Dit and Rs both decrease almost exponentially with increasing frequency. It has been found that Rs is more effective at high frequencies in the accumulation region, while Dit influences the characteristics in the depletion region at low frequencies. Measured capacitance (Cm) and measured conductance (Gm) were improved to corrected capacitance (Cc) and corrected conductance (Gc) to eliminate the effect of Rs at high frequency (1 MHz). Electrical parameters of the fabricated MPS structure and band gap analysis of prepared blend confirms that PEG-PVA blend is a better alternative dielectric material for electronic devices.

Stoichiometric Engineering of Chalcogenide Semiconductor Alloys for Nanophotonic Applications.

A variety of alternative plasmonic and dielectric material platforms-among them nitrides, semiconductors, and conductive oxides-have come to prominence in recent years as means to address the shortcomings of noble metals (including Joule losses, cost, and passive character) in certain nanophotonic and optical-frequency metamaterial applications. Here, it is shown that chalcogenide semiconductor alloys offer a uniquely broad pallet of optical properties, complementary to those of existing material platforms, which can be controlled by stoichiometric design. Using combinatorial high-throughput techniques, the extraordinary epsilon-near-zero, plasmonic, and low/high-index characteristics of Bi:Sb:Te alloys are explored. Depending upon composition they can, for example, have plasmonic figures of merit higher than conductive oxides and nitrides across the entire UV-NIR range, and higher than gold below 550 nm; present dielectric figures of merit better than conductive oxides at near-infrared telecommunications wavelengths; and exhibit record-breaking refractive indices as low as 0.7 and as high as 11.5.

A comparative study of graphene and graphite-based field effect transistor on flexible substrate

In the present era, there has been a great demand of cost-effective, biodegradable, flexible and wearable electronics which may open the gate to many applications like flexible displays, RFID tags, health monitoring devices, etc. Due to the versatile nature of plastic substrates, they have been extensively used in packaging, printing, etc. However, the fabrication of electronic devices requires specially prepared substrates with high quality surfaces, chemical compositions and solutions to the related fabrication issues along with its non-biodegradable nature. Therefore, in this report, a cost-effective, biodegradable cellulose paper as an alternative dielectric substrate material for the fabrication of flexible field effect transistor (FET) is presented. The graphite and liquid phase exfoliated graphene have been used as the material for the realisation of source, drain and channel on cellulose paper substrate for its comparative analysis. The mobility of fabricated FETs was calculated to be $$83\,\hbox {cm}^{2}/\hbox {V}\,\hbox {s}$$ (holes) and $$33\,\hbox {cm}^{2}/\hbox {V}\,\hbox {s}$$ (electrons) for graphite FET and $$100\,\hbox {cm}^{2}/\hbox {V}\,\hbox {s}$$ (holes) and $$52\,\hbox {cm}^{2}/\hbox {V}\,\hbox {s}$$ (electrons) for graphene FET, respectively. The output characteristic of the device demonstrates the linear behaviour and a comprehensive increase in conductance as a function of gate voltages. The fabricated FETs may be used for strain sensing, health care monitoring devices, human motion detection, etc.

Broadband Terahertz Absorption in Graphene-Embedded Photonic Crystals

The absorption in graphene is rather low at terahertz frequencies. Here, we present a graphene-embedded photonic crystal structure to realize broadband terahertz absorption in graphene. The approach provides absorption enhancement in the whole terahertz regime (from 0.1 to 10 THz). It is shown that the average absorption in the graphene-embedded photonic crystal can be enhanced in the multiple propagating bands of the photonic crystals. The absorption efficiency can be further improved by optimizing the characteristic frequency, optical thickness ratio in a unit cell, and the angle of incidence on the photonic crystals. A maximum broadband absorption factor of 28.8% was achieved for fixed alternative dielectric materials. The graphene-embedded photonic crystal is promising for terahertz functional devices with broadband response.

Lifetime and manufacturability of integrated power electronics

In case of battery electric cars, market data show a traditional exponential gradient of sales figures, known from other technology transitions. The worldwide installed wind and photovoltaic capacity show also an exponential gradient. Even the power density of power electronics is growing exponentially.Power electronics is a prerequisite to enable the exponential growth of power density.Requirements on power electronic packaging technologies are electric performance, thermal performance and robust design. Due to the lack of bond wires, SMD capacitors can be mounted close to semiconductors, resulting in a minimization of parasitic inductance. Thermally, the packaging technology benefits from heat spreading inside the copper leadframe and thin dielectric layers. It obtains a thermal resistance of 0.5K/W, and there is potential to further reduce the thermal resistance by alternative dielectric material. The thermal resistance can be further reduced to at least 0.42K/W by the construction of a double side chip cooling.A robust design can be offered by the combination of a chip copper metallization connecting to copper microvias connecting to the top copper layer, which means no difference in coefficients of thermal expansion. On the bottom side, a silver sinter layer offers a reliable connection between chip and leadframe.This paper describes production process optimizations, thermal optimization possibilities, power cycling lifetime measurements and first conductive anodic filament lifetime measurements at 1000VDC. The outlook onto an integrated 120A 700V SiC MOSFET demonstrator is given.

Dielectric Breakdown in Electrowetting-Based Liquid Microactuators

In an electrowetting-based liquid microactuator, two types of insulating materials are used for device operation: an dielectric material to provide capacitance between the liquid and conductor, and a hydrophobic coating at the interface of liquid and insulator. This paper investigates important physical properties for the insulating materials. Several alternative dielectric materials are compared for application in EW chips, breakdown phenomenon of insulating layers with different thicknesses is tested before and after droplet actuation. It appears that the used EW devices have lower breakdown voltages than unused devices, probably due to the locally trapped charges in the insulating layer.

Effects of SiO&lt;sub&gt;2&lt;/sub&gt; Nanoparticles on Dielectric Characteristic of Aloe Vera Paste

Natural Aloe vera paste has been reported as an alternative organic dielectric material. In this study, natural Aloe vera paste incorporated with silicon dioxide (SiO2) nanoparticles (NPs) has been investigated. The natural Aloe vera paste with different weight loading (0.5 to 3.8 wt%) of SiO2 NPs was screen printed on aluminum (Al) layer supported by a soda lime glass substrate and dried at room temperature. The solidified sample with 1.5 wt% of SiO2 NPs showed the lowest leakage current density. Next, the solidified samples were additional dried in an oven at 40°C for 30 minutes to study its effect against room temperature. The additional drying process facilitated cross-linking on natural Aloe vera layer and consequently enhanced the dielectric properties of the natural Aloe vera with 1.5 wt% of SiO2 NPs, whereby leakage current and dielectric constant were decreased and increased, respectively.

Regular Distribution of –OH Fragments on a Si (001)-c(4 × 2) Surface by Dissociation of Water Molecules

Adsorption of a water molecule on a Si (001) surface and its dissociation were studied using density functional theory to study the distribution of -OH fragments on the Si surface. The Si (001) surface was composed of Si dimers, which buckle in a zigzag pattern below the order-disorder transition temperature to reduce the surface energy. When a water molecule approached the Si surface, the O atom of the water molecule favored the down-buckled Si atom, and the H atom of the water molecule favored the up-buckled Si atom. This is explained by the attractions between the negatively charged O of the water and the positively charged down-buckled Si atom and between the positively charged H of the water and the negatively charged up-buckled Si atom. Following the adsorption of the first water molecule on the surface, a second water molecule adsorbed on either the inter-dimer or intra-dimer site of the Si dimer. The dipole-dipole interaction of the two adsorbed water molecules led to the formation of the water dimer, and the dissociation of the water molecules occurred easily below the order-disorder transition temperature. Therefore, the 1/2 monolayer of -OH on the water-terminated Si (001) surface shows a regular distribution. The results shed light on the atomic layer deposition process of alternate gate dielectric materials, such as <TEX>$HfO_2$</TEX>.

A “couplonic” approach to multilayer magneto‐photonic crystals

AbstractIn the frame of an exact (non‐perturbative) formulation of the coupled‐mode theory, we describe the non‐reciprocal properties of a one‐dimensional multilayer magneto‐photonic crystal with alternate dielectric and magneto‐optical materials. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)