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Publications (10)1.48 Total impact

  • M. ZELNER · S. NAGY · A. CERVIN-LAWRY · M. CAPANU · T. BERNACKI · C. DIVITA
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    ABSTRACT: Thin film voltage tunable ferroelectric capacitors on various substrates are promising for use in high power microwave and other RF systems. Benefits of ferroelectric capacitors include miniaturization and integration with other passive devices.Commercialization of ferroelectric components requires compliance with certain industry standards for reliability. For ferroelectric capacitors the requirement to pass the THB test requires a silicon nitride layer in the back end of the process (after interconnect metalization). However the nitride layer deposition process results in a drastic increase in the leakage of the BST capacitors. This effect is attributed to the exposure of the ferroelectric material to atomic hydrogen which is a by-product of the PECVD deposition process.This paper presents results of different passivation materials for ferroelectric capacitors and for a barrier layer which preserves the performance of ferroelectric capacitors during a PECVD nitride deposition. This allows qualification of ferroelectric capacitors to industry reliability standards.
    No preview · Article · Dec 2008 · Integrated Ferroelectrics
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    ABSTRACT: Ferroelectric materials such as (Ba<sub>x</sub> Sr<sub>1-x</sub>) TiO<sub>3</sub> (BST) exhibit a non-zero piezoelectric coefficient under a DC field. The piezoelectric coefficient increases from 0 as the applied DC bias increases from 0V. This gives rise to electrostrictive resonance behaviour in capacitors fabricated with these materials. This paper presents the results of high frequency measurements and simulations of induced piezoelectricity for multilayer BST thin film structures under a 10V DC bias. The Mason model and transmission line theory is used as the basis of the simulation and our work extends it to include the effects of other layers in the passivated capacitor device. High-frequency capacitors with 100 nm thick (Ba<sub>0.5</sub>Sr<sub>0.5</sub>) TiO<sub>3</sub> and Pt electrodes were fabricated on polycrystalline Al<sub>2</sub>O<sub>3</sub> ceramic and Si substrates with an amorphous oxide buffer layer. Correlation between measurements and simulations allowed us to evaluate the piezoelectric coefficient, its switchability and tunability as well as the contribution of the multilayer film structure to the electrostrictive resonance behaviour. The model fits very well with the measurements and can be used to adjust the resonance peaks to the desired frequencies.
    No preview · Conference Paper · Dec 2008
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    ABSTRACT: Power handling capability of tunable microwave devices employing ferroelectric Ba<sub>x</sub>Sr<sub>1-x</sub>TiO<sub>3</sub> film-based varactors: was experimentally measured and analyzed. A microstrip resonator, excited by either harmonic or two-tone microwave signals of elevated power, was selected as an example of tunable test fixture. The nonlinear distortion of the resonant curve under microwave pulsed power and generation of the third-order intermodulation distortion products in microwave resonator, using ferroelectric varactors were measured. Formulas to estimate power handling capability connected with the microwave electric field dielectric nonlinearity and the ferroelectric film overheating are derived for the tunable microwave devices based on ferroelectric films
    Full-text · Conference Paper · Jul 2006
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    ABSTRACT: The power handling capability of tunable microwave devices employing planar and parallel-plate Ba<sub>x</sub>Sri<sub>1- x</sub>TiO<sub>3</sub> film-based capacitors was experimentally measured and analyzed. A microstrip resonator, excited by either harmonic or two-tone microwave signals of elevated power, was selected as an example of tunable test fixture.
    Full-text · Conference Paper · Nov 2005
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    Ivoyl Koutsaroff · Thomas A. Bernacki · Charles Divita

    Full-text · Article · Sep 2004
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    ABSTRACT: In this paper we present the results of the characterization of parallel-plate thin-film (Ba1-x,Srx)TiO3 (BST) capacitors, to demonstrate their suitability for use as decoupling capacitors (a capacitance as high as 0.34 µF and a capacitance density of up to 70 fF/µm2) and as tunable RF components (a small capacitance from 0.5 pF to 16 pF, a high tunability of 4.22:1 at 10 V and a capacitance density of up to 34 fF/µm2). BST films of different compositions, (Ba0.7Sr0.3)TiO3 and (Ba0.5Sr0.5)TiO3, were grown by metal-organic decomposition (MOD) and RF magnetron reactive sputtering on Pt/TiOx/SiO2/Al2O3 ceramic substrates. For large capacitors (2.25 mm2), capacitance and tan δ were measured at low frequencies (1 kHz) using an LCR meter. Smaller capacitors (16 µm2 to 961 µm2) were characterized in the frequency range of 0.01–20 GHz. Capacitance, tan δ and equivalent series resistance (ESR) were extracted from two port scattering parameters obtained using a vector network analyzer (VNA). The relationships between dielectric loss, tunability and commutation quality factor (CQF) vs BST composition and deposition conditions were outlined.
    Full-text · Article · Sep 2004 · Japanese Journal of Applied Physics
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    ABSTRACT: To achieve the level of miniaturization required for hearing aid modules unique 3D chip stacking solutions (S-CSP) have been developed. These architectures utilize multi-layer thin film capacitor technology in combination with high-density thick film based substrates and advanced flip chip, wirebond, and vertical interconnect capabilities. To meet the substrate interconnect requirements demanded by these types of modules an innovative high-density thick film system has been employed. The system includes solid filled Ag/Pd through holes that provide planar front-to-back electrical connection points through the thickness of the substrate, a photoimaged multi-layer thick film dielectric, and a high density etchable gold composition. Dielectric vias less than 100um in diameter and conductor lines/spaces less than 25um can be achieved. For miniaturized multi-chip module (MCM) applications this system can provide a more economical solution than traditional multi-layer thick film because of the significant layer reduction that can be achieved. Other benefits include improved downstream assembly efficiencies and increased yields due to more precise feature definition and elimination of pattern distortion inherent to traditional thick film processes. Built on ceramic substrates the system also offers excellent performance for applications requiring controlled impedance high speed circuitry. This paper describes the process used to fabricate these high-density substrates, outlines the benefits to the overall packaging solution, and highlights some of the applications where this technology has been utilized. Introduction Miniaturization continues to be in high demand for a wide variety of electronic applications. The drive towards smaller form factors coupled with the need to continuously increase functionality yet still maintain good electrical performance presents considerable challenges to the final packaging solution. The needs for miniaturized packaging solutions are particularly prevalent in the hearing aid industry where very small modules are needed to obtain better fit rates particularly in the CIC (completely in the canal) market segment. To achieve this level of miniaturization standard off the shelf approaches are not suitable and more advanced
    Full-text · Conference Paper · Jan 2004
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    ABSTRACT: Ba0.7Sr0.3TiO3 (BST) single and quadruple layer capacitors with Pt electrodes were fabricated together on polycrystalline alumina substrates with a SiO2-based multicomponent amorphous buffer layer (SiO2/Al2O3). This paper presents the results of the characterization of these capacitors, to demonstrate their suitability for application as decoupling (high value) capacitors and as components in tunable RF applications (e.g., phase shifters and filters). BST films of different compositions, (Ba0.7Sr0.3)TiO3 and (Ba0.5Sr0.5)TiO3, were grown by metal-organic decomposition (MOD) and RF magnetron reactive sputtering. The capacitance density of 90–140 nm thick BST films was in the range of 20 to 70 fF/μm 2. Parallel plate capacitors with areas from 16 μm2 to 2.25 mm2 were fabricated using photolithography and ion milling techniques. For large capacitors (0.125 to 2.25 mm2), capacitance and tanδ were measured at low frequencies (1 KHz - 1 MHz) using an LCR meter. Smaller capacitors (16 μm2 to 3600 μm2) were additionally characterized in the frequency range of 50 MHz - 20 GHz. In such case, capacitance, tanδ and equivalent series resistance (ESR) were extracted from two port scattering parameters obtained using a vector network analyzer (VNA). The relationship between dielectric loss, tunability and calculated figure of merit vs. BST composition and deposition temperature was outlined. In addition, loss and ESR at high frequencies was investigated. The typical achieved leakage current density of sputtered BST films for 2.25 mm2 capacitors fabricated on SiO2/Al2O3 was 7.3×10-9 A/cm2 at 300 kV/cm (65 fF/μm2), about 2 times lower than for (Ba0.7Sr0.3)TiO3 films deposited by MOD (1.4×10-8 A/cm2 at 300 kV/cm, 34.5 fF/μm2). Furthermore, the tunability of (Ba0.7Sr0.3)TiO3 deposited by both methods on SiO2/Al2O3 was ∼60% at 350 kV/cm.
    Full-text · Article · Dec 2002 · MRS Online Proceeding Library
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    ABSTRACT: Double layer (DL) Ba0.7Sr0.3TiO3 (BST) capacitors with Pt electrodes have been fabricated with similar growth conditions on different substrates. The substrates used in the present study were r-plane sapphire, polycrystalline alumina Al2O3 (99.6% and 96%), and glazed polycrystalline alumina. BST films were grown by metal-organic decomposition (MOD) method. By varying the annealing conditions which affects the formation of the crystalline structure, significant changes in the dielectric properties of the BST films have been observed. BST films were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Powder X-ray Diffractometer (PXRD). These observations showed that BST films grown at lower temperatures on alumina substrates exhibited the smallest grain size. BST films of the same thickness prepared under the same thermal processing conditions showed higher capacitance when grown on all types of alumina-based substrates compared to those deposited on control SiO2/Si. The higher capacitance on alumina was always associated with larger dissipation factor, and lower or similar leakage current density. The final tuning, of the dielectric properties of BST DL capacitors on non-silicon substrates, was correlated to the initial film formation temperature and post-annealing conditions of the BST films. The leakage current density, of DL BST capacitors fabricated on glazed alumina, becomes smallest when the BST processing temperature was lowered by 100 °C compared to the control SiO2/Si. The typical achieved leakage current density for 1500×1500 μm2 DL capacitors on glazed alumina was 3.8×10-9 A/cm2 at 250 kV/cm (36.5 fF/μm2), about 3 times lower than on SiO2/Si substrates (1.1×10-8 A/cm2 at 250 kV/cm, 31 fF/μm2).
    Full-text · Conference Paper · Jan 2002
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    M Zelner · M Capanu · T Bernacki · A Cervin-Lawry · C Divita
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    ABSTRACT: Thin film voltage tunable ferroelectric capacitors on various substrates show significant promise for use in high power microwave and other RF systems. The commercialization of ferroelectric components requires compliance with certain industry standards. TDDB (Time Dependent Dielectric Breakdown) is a fundamental measure of a dielectric material's aging characteristics under applied bias. Tuning is the main function of a tunable capacitor. Stability of tuning within a required temperature and voltage range is critical. This paper presents the results of a tuning degradation test. Acceleration factors and their limitations are discussed. The relationship of Mean Time to Failure (MTTF) and film grain structure is presented.
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