Dielectric Properties Of Thin Films Research Articles

Ferroelectric tunable coplanar waveguide components for Ku- and K-band and applications

The main objective of this research is to study the effect of inserting a Barium Strontium Titanate (BSTO) ferroelectric tuning layer in coplanar waveguide (CPW) and conductor-backed CPW (CBCPW) components. The modeled components include CPW and CBCPW transmission lines (with and without a dielectric filling between the center conductor and the ground planes). We have modeled the characteristic impedance (Z0), effective dielectric constant (ϵeff), attenuation and dispersion as a function of circuit geometry and the ferroelectric thin-film's dielectric properties over the 10–20 GHz frequency range. We found that the presence of a ferroelectric layer between the transmission line and the ground planes improves the percentage change in ϵeff by almost two-fold with respect to a CPW deprived of this layer. This result is significant, as one could obtain larger frequency tunability with relatively lower applied fields compared to regular CPW or microstrip lines.

Microwave Properties of Strontium Barium Niobate Thin Films Grown by Pulsed Laser Deposition

AbstractStrontium barium niobate (SrxBa1−xNb2O6 - SBN) with 0.25≤x≤0.75 is a ferroelectric material of interest for diverse optoelectronic applications. Dielectric properties of bulk SBN crystals were comprehensively studied over 30 years ago for a range of compositions and at frequencies up to 30 MHz, but there is little information on properties at higher frequencies. In particular, and up to the best of our knowledge, there are no published results about SBN thin film dielectric properties at high frequencies. For the study reported here, SBN thin films with x = 0.61 were grown on MgO and LaAlO3 substrates by Pulsed Laser Deposition (PLD). Films with good crystallinity and oriented with c-axis normal to the substrate surface were obtained on both types of substrates, while films on MgO had much better texture due to better lattice matching. Interdigital electrode (IDE) capacitors and coupled microstrip phase shifters (CMPS) were fabricated with both types of samples in order to study dielectric response. Capacitance of the IDE capacitors was measured at 1 MHz as a function of temperature and bias voltage, revealing very low losses but poor capacitance tunability, particularly for samples on MgO. Response of the CMPS structures was measured at room temperature and at high frequencies, up to 21 GHz. Insertion losses were measured up to 28 GHz.

On-wafer characterization of thermomechanical properties of dielectric thin films by a bending beam technique

A bending beam technique has been developed for on-wafer characterization of thermomechanical properties of dielectric thin films including Young’s modulus (E), the coefficient of thermal expansion (CTE), and the Poisson ratio (ν). The biaxial modulus E/(1−ν) and CTE were determined by measuring the thermal stresses of the dielectric film as a function of temperature on two different substrates. The Poisson ratio and Young’s modulus were determined by measuring the temperature dependence of the thermal stress of periodic line structures of the dielectric film. Three dielectric thin films were selected for this study, consisting of silica made from tetraethylorthosilane (TEOS), hydrogen silsesquioxane (HSQ), and biphenyltetracarboxylic dianhydride-p-phenylene diamine (BPDA-PDA). The deduced biaxial modulus and CTE are 77 GPa and 1.0 ppm/°C for TEOS, 7.07 GPa and 20.5 ppm/°C for HSQ, and 11.1 GPa and 3.4 ppm/°C for BPDA-PDA. The Poisson ratio is determined to be 0.24 and Young’s modulus is 59 GPa for the TEOS film. The error limit and the valid range of E/(1−ν) and CTE for applying this technique are also discussed.

Dielectric Investigation of BaTiO3 Thin-Film Capacitor

The dielectric properties of BaTiO3 thin film were investigated on a highly c-axis-oriented epitaxial thin crystal. It was confirmed by X-ray diffraction that the film thickness was 120 Å and that it was high-quality single-crystal film. The spread of crystal orientation of the BaTiO3 thin film was the same as that of SrTiO3 substrate. However, the dielectric properties of this thin film were different from those of the BaTiO3 bulk crystals and were explained by the space-charge effect. The space-charge polarization of this film strongly depends on temperature and this behavior was observed after the incubation time had passed. The experimental results are discussed in terms of the interaction between the polarities of domain and space charges.

Measurement of thermal properties of thin dielectric films and anisotropic solids by ac hot-strip method

The present work deals with the foundations of the theory of the method of measuring the thermal properties of anisotropic solids and thin dielectric films deposited onto them. The experimental setup is briefly described. The authors demonstrate the possibility of measuring a set of thermal properties of solids by means of recording the amplitude and phase of temperature oscillations of a strip, which has a width comparable with the attenuation length of a temperature wave in the sample. The paper offers the results of measurements of the heat capacity, thermal conductivity, thermal diffusivity and thermal activity of leucosapphire. The thermal conductivity of an SrTiO3 film about 2 μm thick sputtered onto a single crystal of leucosapphire was determined by measuring the temperature oscillation amplitude at various frequencies.

Dielectric Properties of Radio Frequency Magnetron Sputter Deposited Zirconium Titanate‐Based Thin Films

We have studied the dielectric properties of thin film zirconia‐titania‐based mixed oxide compositions. Films of different Zr/Ti ratios were developed by radio frequency magnetron sputtering, and the effect of dopant addition to the composition were also investigated. We present a comparison of the electrical properties of zirconium titanate thin film capacitors in metal‐insulator‐semiconductor and metal‐insulator‐metal structures, and discuss the effect of process parameters on film properties. Stoichiometric (1:1 Zr:Ti), 320 Å zirconium titanate films on silicon exhibited an effective dielectric constant of 17 at 1 MHz. This is equivalent to an thickness of 73 Å. For 2500 Å thin zirconium titanate films on silicon, the dielectric constant was determined to be 37 at 1 MHz. On platinized silicon, the dielectric constant of 450 Å zirconium titanate films was 33. This corresponds to an equivalent thickness of 53 Å. Direct current resistivities improved by nearly two orders of magnitude by modifying the film composition with an addition of tin oxide. Tin modification also resulted in a significant improvement in the film dc breakdown characteristics, and we have achieved dielectric breakdown field greater than 7 MV/cm. Zirconium titantate‐based thin films display high resistivity and high dielectric constant, and are highly promising for ultra‐large scale integration applications. These films provide large capacitance in small area, and hence, higher charge storage capacity.

Measurement of the thermal properties of thin dielectric films by a probe technique with periodic heating. I. Theory underlying the method

The foundations of the theory underlying a method for measuring the thermal properties of anisotropic solids and thin dielectric films deposited on them are examined. An analysis of the solutions is performed, making it possible to establish the limiting possibilities of the periodic-heating technique and the conditions needed for an experiment that would permit measurement of the specific heat and the thermal conductivity of films with good accuracy.

Measurement of the Electrical Properties of High Performance Dielectric Materials for Multichip Modules

Multichip modules provide short chip‐to‐chip interconnects in order to take advantage of the high speeds available in integrated circuits. One multichip approach utilises layers of embedded microstrip. In order to achieve the highest possible speed, it is necessary to use metals and dielectrics which have low relative dielectric constants and low loss. Polymer and polyimide dielectric materials hold great promise in MCM applications; however, their high frequency characteristics are often not well known. Since thin film dielectric properties may differ from the bulk properties, it is important to be able to determine the dielectric properties using on‐wafer measurement techniques rather than more conventional techniques. This paper focuses on some of the techniques available and discusses the advantages and shortcomings of different techniques for measuring dielectric properties.

Characterization by guided wave of instabilities of optical coatings submitted to high-power flux: thermal and third-order nonlinear properties of dielectric thin films

We study the reversible refractive index variations of optical thin films submitted to a high-power light flux. As a preliminary step, we study the thermorefractive coefficient ?n/?T and the laser damage threshold of our materials. From the hypothesis of a localized optical Kerr-type effect, we use the m-line technique to estimate the nonlinear refractive-index coefficients n(2) of TiO(2), Ta(2)O(5), and ZnS films with continuous illumination. Very large values of n(2) are found for the films obtained by conventional evaporation condensation. On the other hand, the study of the change in the decoupling direction of a low-power light guided in a layer disturbed by a pulsed YAG laser gives a first analysis of the phenomena versus time.

Influence of substrate temperature on the properties of oxygen-ion-assisted deposited CeO2 films

Substrate temperature and ion bombardment during deposition have been observed to modify significantly the optical and structural properties of dielectric thin films. Single-layer films of CeO2 have been deposited by electron beam evaporation with simultaneous oxygen-ion bombardment using a Kaufman broad beam ion source and maintaining the substrates at elevated temperature. A systematic study has been made on the influence of (a) substrate temperature in the range ambient to 300 °C, (b) ion energy in the range 300–700 eV, and (c) ion current density 100–220 μA/cm2 on optical properties such as refractive index, extinction coefficient, inhomogeneity, packing density, and structural properties. The refractive index increased with in increase in substrate temperature: ion energy up to 600 eV and ion current density. Homogeneous, absorption free and high index (2.48) films have been obtained at 600 eV, 220 μA/cm2 and at substrate temperature of 300 °C. The packing density of the films was observed to be unity for the same deposition conditions. Substrate temperature with simultaneous ion bombardment modified the structure of the films from highly ordered to fine grain structure.

Microstructural and dielectric properties of BaTiO 3 thin films prepared by atom beam sputtering

Amorphous BaTiO 3 films were deposited on glass plates overlayered with platinum by atom beam sputtering at different substrate temperatures, and the effects of post-annealing at 923 K on the crystallization behavior and dielectric properties investigated. The possibility for improvement of dielectric properties of thin films through the crystallization of amorphous phases is discussed.

Structural properties of In-Se thin films prepared by direct evaporation of InSe chunk

In-Se films were deposited by direct evaporation of an InSe chunk using hot-wall-type evaporation equipment. The crystal structure was studied by X-ray diffraction using the Cu Kα line and the crystallographic properties of the films, such as the half width of the diffraction peak and the standard deviation of the rocking curve, were estimated as a function of the preparative conditions. It was found that films with a thickness above the critical value had a preferred (0001) orientation and that this critical thickness depended both on the substrate and on the source temperatures. In the present study, the films grown at 320°C with T so in the range from 550 to 570°C had the highest orientation.

Electrical and switching properties of InSe amorphous thin films

In this work electrical and switching properties of InSe thin films have been studied. The semiconductor compound InSe was obtained by direct synthesis from stoichiometric amounts of spectroscopically pure indium and selenium. By slow cooling of the synthesized InSe a polycrystalline material is obtained. The amorphous films were obtained by thermal evaporation under vacuum of the polycrystalline material on glass or pyrographite substrates. From electrical measurements, it was found that for all films the dark electrical resistivity decreases with an increase in film thickness and temperature. The InSe compound exhibits non-linear I–V characteristics and switching phenomena. The threshold voltage decreases with increasing annealing temperature and increases with increasing film thickness.

誘電体薄膜の高温物性 （Ｉ）

誘電体薄膜の高温物性 （Ｉ）

高温における誘電体薄膜の電気的特性

高温における誘電体薄膜の電気的特性

Studies of the polyparaphenylene/aluminium interface

The dielectric properties of thin film Al/polyparaphenylene/Al structures have been investigated in the frequency range from 10 −2 to 5 × 10 5 Hz. Experimental data suggest the existence of interfacial layers at the polymer/metal contacts. An equivalent circuit analysis, taking into account the dielectric response of these elements, is presented. To clarify the nature of the contact, X-ray photoelectron spectroscopy (XPS) has been performed on polyparaphenylene (PPP) films covered with Al layers. Displacements of the C(1s), O(1s) and Al(2p) lines lead to the conclusion that a chemical reaction between carbon, oxygen and aluminium occurs at the interface to form a metal-oxygen-polymer complex which is found to be responsible for the electrical a.c. behaviour of Al/PPP/Al structures.

Dielectric and high Tc superconductor applications of sol-gel and modified sol-gel processing to microelectronics technology

Microelectronic applications for sol-gel processed dielectric materials (e.g. dopant sources, resist patterning, substrates, planarization layers) are briefly reviewed. The preparation and properties of dielectric thin films of a ladder siloxane, useful for some of these applications, are described. The properties of an as-spun film of this material are intermediate between those of an organic (e.g. a resist) and an inorganic (e.g. an oxide). These organosilicon polymers can also be used as precursors for the preparation of inorganic oxides; silica, phosphosilicate, borosilicate and borophosphosilicate thin films have been prepared. The amount of boron and phosphorus incorporated appears to be limited by the organosilicon functionality. Conversion to the inorganic oxide can be accomplished by either pyrolysis or plasma oxidation. Also discussed is the processing and properties of an aqueous based sol-gel process for the preparation of superconducting YBa 2Cu 3O 7− y , a material which could have application as a thick film chip-carrier metal interconnect. Materials prepared using this process demonstrate an excellent resistivity versus temperature superconducting transition behavior but have low critical current densities.

Effects of heat treatment on the optical and structural properties of InSe thin films

Thin films of indium selenide of different thicknesses are deposited on glass substrate by vacuum evaporation. The optical gaps (E) are determined from the absorption spectra of as-deposited InSe films. The value of E of a-InSe films is found to increase with the thickness of the films. The InSe films are heat treated at different elevated temperatures from 423 to 573 K. The values of optical gaps E of InSe films are also found to increase with temperature of heat treatment. The effect of thickness and temperature of heat treatment on the optical gap (E) of the film is interpreted in terms of the density of state model of Mott and Davis. The valence band density of states of a-InSe films is calculated from the optical absorption data. The variation of valence band density of states with temperature of heat treatment is observed in the case of a-InSe films. X-ray diffraction spectra are taken for both, as-deposited and heat treated InSe films. A radial distribution function (RDF) analysis of X-ray diffraction (XRD) spectra is made to get an insight into the structural information of the specimens. From the results related to RDFs of the specimens it is shown that in case of InSe a transition from the amorphous to the crystalline state takes place at 573 K. Mittels Vakuumaufdampfung werden dunne Schichten von Indiumselenid verschiedener Dicke auf Glassubstraten aufgebracht. Die optischen Bandlucken (E) werden aus dem Absorptionsspektrum der InSe-Schichten unmittelbar nach der Abscheidung bestimmt. Der Wert E der a-InSe-Schicht nimmt mit der Dicke der Schichten zu. Die InSe-Schichten werden bei verschiedenen erhohten Temperaturen zwischen 423 und 573 K getempert. Die Werte der optischen Bandlucken E der InSe-Schichten nehmen mit der Temperatur der Warmebehandlung ebenfalls zu. Der Einflus der Dicke und der Temperatur der Warmebehandlung auf die optische Bandlucke (E) der Schicht wird mit dem Modell der Zustandsdichte von Mott und Davis erklart. Die Zustandsdichte des Valenzbandes der a-InSe-Schichten wird aus den optischen Absorptionswerten berechnet. Eine Anderung der Valenzbandzustandsdichte mit der Temperatur der Warmebehandlung wird im Falle der a-InSe-Schichten beobachtet. Rontgenbeugungsspektren werden sowohl fur InSe-Schichten unmittelbar nach dem Abscheiden als auch fur getemperte Proben aufgenommen. Eine Analyse der radialen Verteilungsfunktin (RDF) der Rontgenbeugungsspektren (XRD) wird durchgefuhrt, um strukturelle Informationen uber die Proben zu erhalten. Aus den mit RDF verbundenen Ergebnissen wird gefunden, das im Falle des InSe ein Ubergang vom amorphen zum kristallinen Zustand bei 573 K eintritt.

Interpretation of dielectric properties of thin film Al/Al 2O 3/Au structures

On the basis of experimental data previously presented, the dielectric properties of thin film Al/Al 2O 3/Au structures were investigated in the frequency range 10 -2−10 +5Hz. The results of the measurements suggested the existence of two laws of dispersion of the complex dielectric susceptibility, each obeying the empirical relation χ′(ω)∝χ≈(ω)∝ω n−1 , with n = 0.14 in the low frequency range and n = 0.88 at higher frequencies. In this paper, an equivalent circuit is proposed; it takes into account, firstly, the two laws of dispersion which coexist over the whole temperature (393–505 K) and frequency ranges studied and, secondly, the existence of a thin interfacial zone at the electrode(s), which is less conducting than the bulk of the dielectric.

Characterization of the dielectric properties of thin films

The cooperative cluster model of dielectric relaxation is outlined and applied to a representative range of thin film materials. It is shown that the full spectral response of the dielectric dispersions observed can be described in terms of the cluster model and that the characteristic cooperative parameters can be used to gain an insight into both the local and the long-range structure of the films.