Dielectric Constant Materials Research Articles

Effect of thermal annealing on the structure and properties of plasma enhanced chemical vapor deposited SiCOH film

The development of high-performance integrated circuit chips and the shrinkage of feature sizes according to Moore’s law bring forward continuously the requirements for low dielectric constant (low-k) materials with various excellent properties in the back-end-of-the-line (BEOL) interconnect. Porous SiCOH films prepared by plasma enhanced chemical vapor deposition (PECVD) through a porogen approach are widely applied to industry and extensively studied. Thermal annealing is an important process for fabricating the porous low-k films, which has a great influence on film structure as well as properties. SiCOH films are deposited by PECVD using tetraethoxysilane and limonene as precursors, and annealed at 450 ℃ for 1.5 h under nitrogen atmosphere. The evolutions of film structure and properties during thermal annealing are revealed, and the reaction mechanism for structure change is also proposed. Fourier transform inferred spectroscopy and solid state nuclear magnetic resonance results show that the as-deposited film is an organic-inorganic hybrid film composed of various kinds of Si-O-Si, -CHx, Si-O-CH2CH3, etc. The organic component is removed almost completely during thermal annealing, making a porous film with a Si-O-Si inorganic skeleton. The skeleton is also rearranged at the same time. Deconvolution of the Si-O-Si absorption band of the FTIR spectrum reveals that the cage-like Si-O-Si occupies the major part for both as-deposited and annealed films, while the amount of silicon suboxide Si-O-Si decreases and that of network Si-O-Si increases during thermal annealing, making the film more robust. More C=C and Si-C are formed through chemical reactions between Si-H, -CHx and Si-O-CH2-CH3, and crosslinking is further enhanced. Nitrogen adsorption/desorption isothermal measurement reveals that a large number of micropores with diameter less than 2-3 nm are created during thermal annealing, which is consistent with the removal of organic groups and the existence of cage-like Si-O-Si. As a result, both the refractive index and dielectric constant decrease significantly from 1.476 (λ =630 nm) and 3.45 to 1.365 and 2.60, respectively. Because of the increase of C=C after annealing, extinction coefficient and leakage current density increase. Although there is a shrinkage of 14.7% in film thickness and a reduction of mechanical properties after annealing, the Young’s modulus is still larger than 4 GPa. Considering all kinds of properties, the obtained film appears to be a competitive candidate as inter layer dielectrics in the BEOL interconnect of integrated circuits.

Complex Permittivity Determination From Far-Field Scattering Patterns

An accurate knowledge of the complex permittivity value of materials is compulsory when performing experimental electromagnetic applications. Unfortunately, these values are not so obvious to determine in practice. In this letter, we propose a novel approach for determining the complex dielectric constant of materials. This method combines free-space far-field scattering pattern measurements with a Bayesian procedure, which fully exploits the measurement uncertainties. Therefore, the measured values weighted according to their experimental accuracy are incorporated in the permittivity determination algorithm. In this letter, the samples are all shaped as spheres in order to benefit from efficient Mie scattered field computations. The dielectric properties of typical plastic samples are first determined and compared to values found in the literature in order to assess the validity and the accuracy of the proposed methodology. A more “exotic” sample extracted from a microwave absorber, which is a polyurethane foam charged with carbon particles, is also analyzed.

Effect of Graphite on the Microwave Susceptibility of Cement Foam Concrete

The reduction of the dielectric constant of materials is in favor of the improvement of the microwave susceptibility. A great amount of micro-pores in the cement paste introduced by a foaming agent could reduce the dielectric constant of a cement matrix, as well as reducing its apparent density. The microwave susceptibility of cement foam concrete was determined by the arch reflection method in the range of 8–18 GHz. Effect of graphite content, porosity, surface roughness, moisture content and age over the microwave susceptibility was studied. Results showed that this capacity was enhanced with the increase of graphite content, being the optimal 15 wt.%. Porosity and open porosity also help matching impedance on the surface of sample. The increase of the moisture content resulted in the fluctuation of the microwave susceptibility of concrete, while the age had no significant effect.

Radiation of Open-Ended Rectangular Waveguide into Terminating Rectangular Cavity: Application to the Measurement of the Complex Dielectric Constant of Substances

The problem of radiation of open-ended rectangular waveguide into a rectangular cavity is tackled. The cavity is assumed to be filled with material of complex dielectric constant in the form of powder or liquid. The cavity is directly connected to the waveguide through its open end. The work main objective is to solve for the electromagnetic fields inside the waveguide and the cavity in order to estimate the value of the equivalent admittance of the cavity in terms of its dimensions, the complex dielectric constant of the substance filling it and the waveguide dimensions. Successful and good agreement is obtained between the obtained results and those obtained by using the commercial software HFSS. Further to that, the work paves the way for an accurate and efficient technique to measure the complex dielectric constant of substances filling the terminating cavity.

Optical Constants of SiO2 Films Deposited on Si Substrates

SiO2 films were deposited on single-crystalline silicon substrates by ion beam sputtering technology. Optical constants of SiO2 films are calculated from spectroscopic ellipsometry data, transmittance spectra and reflectance spectra by WVASE32 software, and the best fitted method is obtained for calculating optical constants of dielectric materials in the ultraviolet-visible-infrared (UV-VIS-IR) range. In the UV-VIS-NIR spectral range, refractive indices of SiO2 films are calculated separately by both ellipsometry data and reflectance spectra, and the obtained results are almost the same. Complex dielectric functions of SiO2 films in the IR spectral range are accurately calculated with infrared transmission spectra using the GenOsc model. The obtained accuracy complex refractive index of SiO2 films in the wavelength region from 0.19 μm to 25 μm is of great importance for the design of high quality coatings, such as ultra-low loss coating.

Simulations of electrical asymmetry effect on N2-H2 capacitively coupled plasma by particle-in-cell/Monte Carlo model

A N2-H2 capacitively coupled rf discharge has potential applications in etching of organic low dielectric constant (low-k) material for microelectronics technology. In this paper, we investigate the characteristic and electrical asymmetry effect (EAE) on the N2-H2 capacitively coupled plasma used for low-k material etching by particle-in-cell/Monte Carlo (PIC/MC) model, in which the two frequency sources of 13.56 MHz and 27.12 MHz are applied separately to the two electrodes in geometrically in symmetry. It is found that the plasma density profiles, the ion flux density profiles and the energy distribution of ion bombarding electrodes can be changed by adjusting the phase angle θ between the two harmonics. When the phase angle θ is 0°, the density of primary ion (H3+) near low frequencie electrode (LFE) (wafer) is smallest, whereas flux and average energy of ion (H+, H3+, H2+) bombarding LFE are biggest; if the phase angle θ is tuned from 0° to 90°, the dc self-bias increases almost linearly from -103 V to 106 V, ion flux bombarding the LFE decreases by ±18%, the maximum of the ion bombarding energy at the LFE decreases by a factor of 2.5. For the N2-H2 capacitively coupled rf discharge, for the case of two frequencies (13.56 MHz/27.12 MHz) applied separately to the two electrodes, can realize separate control of ion energy and flux via the EAE, and is generally in qualitative agreement with experimental and modeling investigation on the Ar and O2 plasma for a dual-frequency voltage source of 13.56 MHz and 27.12 MHz is applied to the powered electrode. This work supplies a references basis for experimental research and technology that the EAE on the H2-N2 plasmas is used for organic low-k material etching process.

Research on Mechanical Design with Beidou GPS Navigation Antenna Design Terminal

With advances in technology and machinery manufacturing technology, the satellite navigation system plays a more and more important role in the modern society. People demand increasingly for satellite navigation. Satellite navigation is increasingly used in military systems, so military and civilian value is higher and higher. For the satellite signal reception, microstrip antenna plays an indispensable role. As the mechanical design of microstrip antenna is simple, easy manufacture, low cost, smaller size, lighter weight, with the overall unity of active devices and integrated circuit, etc. The successful development of high dielectric constant ceramic material enables the area of microstrip antenna to narrow several times. Microwave dielectric ceramics material has some merits such as high dielectric constant, thermal stability and excellent characteristics of small dielectric loss. Different dielectric constant substrate can be prepared through changing and doping modification of process parameters, including the relative dielectric constant of microwave dielectric ceramics for more than a few dozens which can be used for different microwave frequencies. Those are important reasons for promoting the development of microstrip antenna.

The slow light in the closed-packed face-centered cubic photonic crystal: characteristics and application design

Using the plane wave expansion method, we calculated the energy band distribution of face-centered cubic (FCC) photonic crystals in the reciprocal lattice space. The influences of various dielectric constant materials on the properties of slow light are discussed. The results show that, in the close-packed hollow spherical FCC photonic crystal, the group velocity of light can be slow down to the velocity about $$10^{-4}c$$ . And the slow light effect tends to occur more strongly in the hollow spherical structure in comparison with the dielectric spherical structure. The possible applications of the slow light effect in the 3D photonic crystal are proposed for solar cells and optical communication devices.

Water Content Detection for Fine Iron Powder Based on Capacitance Sensor

The water content of fine iron powder is an important parameter to evaluate the fine iron powder price, and there is very important practical significance for rapidly measuring water content of the fine iron powder during manufacturing and trading. So water content detecting method is explored for fine iron powder based on capacitance sensor. The capacitance size depends on the dielectric constant of material between the plates, and the capacitance value reflects the iron powder water content. The water content measurement system for the fine iron powder is designed based on the principle above. The measurement probe components and its testing mechanics are researched, and capacitance measurement circuit and single chip control system of STC89C55 are designed. The software programming and debugging for single chip control system are completed. The experimental results show that the capacitive measurement method of water content for fine iron powder is feasible and easy to implement real-time or rapid monitoring.

Dielectric properties of carbon-, silicon-, and germanium-based polymers: A first-principles study

A knowledge of factors that control the electronic structure and dielectric constant of materials would be valuable in the design of new insulators with attractive dielectric properties. In an attempt to systematically and directly understand the role of chemical composition and atomic configuration in determining such properties, we have studied (using first-principles computations) nine homopolymer systems based on $XY$${}_{2}$ building blocks, where $X=\mathrm{C}$, Si, or Ge and $Y=\mathrm{H}$, F, or Cl. Two possible generic configurations were explored, and our computations utilized dispersion-corrected semilocal exchange-correlation functionals as well as hybrid functionals. Correlations between stability, electronic structure features, infrared intensities, and the dielectric response are established across the chemical and configurational space considered. Homopolymers containing GeF${}_{2}$ or GeCl${}_{2}$ building blocks are identified as particularly promising. These systems display large dielectric constant values (regardless of the underlying crystal structure) and may display a large band gap for particular configurations. The design of a polymer insulator with optimal dielectric constant and band gap may require consideration of heteropolymers (e.g., involving CH${}_{2}$ and GeF${}_{2}$ building blocks). We provide a convenient strategy for the rapid exploration of that extended chemical and configurational space.

Dielectric property of binary phase composite and its interface investigated by electric force microscope

Dielectric property of two-phase stack-up sample is studied by electric force microscopy (EFM). Highly oriented pyrolytic graphite (HOPG)/polyethylene(PE) and mica/PE are fabricated. The phenomenon that phase shift (Δθ) of conducting probe varys with dielectric constant of material is discovered near the interface between the two materials by using phase detection EFM. The characteristic curves of tan(Δθ) versus tip voltage VEFM are of parabolic type. Quadratic coefficient increases with dielectric constant ε increasing. An approach to the qualitative analysis of the dielectric property near the interface between different material at the micro/nanometer scale, is provided in this paper.

Synthesis and characterisation of gold nanoparticle doped ceria-rice husk silica nanocomposites derived from biomass

To realise high performance in IC devices, it is necessary to reduce the RC delay, cross talk, and power consumption. An effective method to make these reductions is to decrease the parasitic capacitance by employing a low dielectric constant (low-k) material in the intermetal dielectrics (IMD). The present research topic deals with the synthesis and characterisation of gold doped in ceria-silica, derived from rice husk biomass materials. Large amount of silica recovered from waste rice husk silica, hence the silica materials derived from waste product can be the low cost and used for potential application such as low-k dielectric material development. Gold doping on ceria-mixed silica derived from rice husk is carried out by insitu method (Au/Ce-silica-A) and deposition-co precipitation method (Au/Ce-silica-B). Au/Ce-silica-A and Au/Ce-silica-B shown the low-k dielectric constant compared to bulk ceria-silica.

Moisture content prediction of Iranian wheat using dielectric technique.

The moisture measurement is the most important criteria in harvesting and post harvesting processing of wheat. This paper investigates the moisture dependent dielectric constant and calibration equation of three most cultivated wheat varieties in Iran. An instrument with a cylindrical capacitive sensor was used to measure the dielectric constant of grain at different moisture contents. Samples were prepared at five levels of moisture content. To validate the proposed equations, the dried material dielectric constant was estimated and compared with the measured ones. Homographic regression models showed an acceptable prediction of dried wheat dielectric constant. Results showed that the calibration equation obtained for Shahriar variety was able to predict the moisture content of other varieties confidently. The lowest value of R (2) = 0.985 between predicted and reference moisture content for Tajan variety is still a good result.

1 × 3 Microstrip Line-fed Metal-plated Split U-shaped Omnidirectional Ultra-wideband Monopole Antenna

In this article, a parallel metal-plated split U-shaped omnidirectional ultra wideband (UWB) antenna fed by a novel 1 × 3 microstrip line is proposed. Printed monopole antennas fabricated on a substrate offer impedance bandwidth which can cover UWB. However, radiation pattern varies significantly over the bandwidth. The cross polar component increases with frequency and the pattern degrades from the desired omnidirectional characteristics. Omnidirectional radiation bandwidth can be increased significantly by decreasing the substrate thickness and using substrate material of low dielectric constant. With the use of the proposed feeding arrangement, parallel metal-plated split U-shaped monopole antenna shows omnidirectional radiation pattern. The proposed metal-plated structure using foam as dielectric is designed, fabricated, and tested. The measured VSWR is <2 over 3.1 to 10.6 GHz frequency band. The antenna offers high efficiency, stable gain, small group delay variation, and its radiation patterns indicate its suitability for UWB applications.

Thermo-electro-mechanical response of 1–3–2 piezoelectric composites: effect of fiber orientations

A micromechanics-based analytical model is developed to evaluate the performance of 1–3–2 piezoelectric composite where both matrix and fiber materials are piezoelectrically active. A parametric study is conducted to investigate the effects of variations in the poling characteristics of the fiber phase on the overall thermo-electro-mechanical behavior of a 1–3–2 piezocomposite. The performance of the 1–3–2 composite as a transducer for underwater and biomedical imaging applications is analyzed. The proposed model is capable of predicting the effective properties of the composite subjected to thermo-electro-mechanical loading conditions. The predicted variations in the effective elastic, piezoelectric and dielectric material constants with fiber volume fraction are nonlinear in nature. It is observed that the influence of thermal effects on effective properties of the composite also induces polarization in the composite. The analytical results show that an appropriate selection of the poling characteristics of the individual fiber and matrix phases could lead to the development of a piezocomposite with significant effective properties.

The study on stress-cone based on HTS cable terminal

Our research aims at improving the performance of 35kV class stress-cone for HTS cable terminal. Firstly, the equivalent circuit model of a stress-cone is constructed for simulation. The relation between the sag voltage of each layer can be characterized by structural and material parameters, such as the stress-cone’s plate length, plate radius, insulating material thickness and dielectric constant. Secondly, the simulation based on ANSYS is developed for analyzing the electric field of stress cone of HTS cable terminal, by altering the length of step and insulation material parameter of stress cone, we get the voltage of each plate layer, horizontal electric field and vertical electric field, and the influence of stress-cone parameter on stress cone electric field is analyzed.

Low Temperature Sintering of BaO–ZnO–TiO&lt;sub&gt;2&lt;/sub&gt; Ceramics for LTCC Applications

In order to develop a new middle dielectric constant LTCC materials, the effects of BaO–ZnO–TiO2–B2O3–SiO2(BZTBS) and/or BaCu(B2O5)(BCB2) on the phase composition, microstructure and microwave dielectric properties of BaO–ZnO–TiO2 ceramics were investigated by solid-state reaction. It was found that BCB2 mainly worked as sintering aids to lower the sintering temperature and the key role of BZTBS was to affect the phase composition in favour of showing a high Q×f value. Therefore, when 5wt% BZTBS+6wt% BCB2 were co-doped, the sintering temperature was down to 850°C, and the microwave dielectric properties were improved significantly because the densification and grain size distribution were not only improved but also the phase composition was controlled. At last, this ceramics sintered at 850°C for 0.5 h showed good microwave dielectric properties: εr=28.4, Q×f=8,030 GHz and τf=2 ppm/°C. Also, it was compatible with Ag electrodes, so it was a promising candidate for LTCC application.

Impedance spectroscopy and structural properties of the perovskite-like Sn(Ba,Sr)O3 stagnate

An exhaustive study of structural, electrical and transport properties on the perovskite stagnate Sn(Ba,Sr)O3 was performed. Samples of SnBa1−xSrxO3 with 0≤x≤1.00 were prepared by the solid state reaction method. The crystallographic structure was studied by X-ray diffraction experiments and Rietveld refinement using the GSAS code. Results reveal the material synthesized in a cubic structure (space group Pm3̄m, #221) for 0≤x≤0.50 and in an orthorhombic (space group Pnma, #62) for x>0.50. The approximate grain size was found from experiments' Scanning Electron Microscopy. The electric response was studied by the Impedance Spectroscopy technique from 10.0mHz up to 0,10MHz. Electric polarization measurements for SnSrO3 and SnBaO3 were determined through curves of polarization as a function of applied electric field, which reveal the ferroelectric character of the material. From the saturation polarization the dielectric constants of materials were calculated.

Circular Polarized Dielectric Resonator Antenna for Portable RFID Reader Using a Single Feed

A new design of circular polarized elliptical dielectric resonator antenna (DRA) with single feed for handheld radio frequency identification (RFID) reader is presented. The elliptical dielectric resonator antenna with an aspect ratio of 1.5 is used. This design has achieved 66.7 MHz impedance bandwidth (for S11 &lt; –10 dB) by using material with dielectric constant material (εr = 12) in conjunction with coaxial probe feed in free space. The DRA models are simulated using two different numerical techniques, the finite element method and the finite integral technique. The numerical results of the two different computational methods approache are investigated and compared. The results are in good agreement within the desired frequency band, 5.65 GHz – 5.95 GHz. A model for a handheld RFID reader device including the elliptical DRA in the presence of human hand models is, also, investigated. The return loss is &lt;10 dB over the frequency range of 5.49– 6.967 GHz resulting in frequency bandwidth of 1.47 GHz. A high front to back ratio and gain of 5.726dBi are obtained.

Transmission Fourier Transform Infra-red Spectroscopy Investigation of Structure Property Relationships in Low-k SiOxCy:H Dielectric Thin Films

ABSTRACTIn order to understand the structure property relationships for inorganic low dielectric constant (i.e. low-k) materials, transmission Fourier Transform-Infrared (FTIR) spectroscopy has been utilized to study the local bonding structure in various plasma enhanced chemically vapor deposited low-k materials in the SiOxCy:H phase diagram. The FTIR measurements were combined with additional mechanical, electrical, and optical property measurements to elucidate the structure property relationships for these materials. The combined measurements show that increased incorporation of terminal methyl bonding results in a decrease in network bonding that manifests itself in a reduction in mass density, dielectric constant, refractive index, Young’s modulus and many other important material properties.