bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical and Physical Characterization of Ultrathin Silicon Oxynitride Gate Dielectric Films Formed by the Jet Vapor Deposition Technique
Authors: Karamcheti A. , Watt V.H.C. , Luo T.Y. , Brady D. , Shaapur F. , Vishnubhotla L. , Gale G. , Huff H.R. , Jackson M.D. , Torres K. , Diebold A. , Guan J. , Gilmer M.C. , Brown G.A. , Bersuker G. , Zeitzoff P. , Tamagawa T. , Guo X. , Wang X.W. , Ma T.P.
Published: April 2011

This paper describes the electrical and physical characteristics of ultrathin Jet Vapor Deposited (JVD) Silicon Oxynitride films. Capacitance-Voltage measurements indicate an equivalent oxide thickness (EOT) of less than 2 nm, taking into account the quantum-mechanical correction. These films have leakage currents almost two orders of magnitude lower than thermal oxide of the same equivalent thickness. Measurements on NMOSFETs with 0.15 μm of channel length demonstrate excellent electrical properties, including high drive currents (∼0.5 mA/μm @ Vd=Vg–Vt=l.5 V), low sub-threshold swings (∼72 mV/decade), and high transconductance (∼0.36 mS/μm @ Vd=1.5 V). These films were also analyzed using a variety of physicochemical methods, including Total X-ray Fluorescence (TXRF), Atomic Force Microscopy (AFM), Nuclear Reaction Analysis (NRA), Low Energy (500 eV) Secondary Ion Mass Spectrometry (SIMS), and Transmission Electron Microscopy (TEM). Surface metal concentrations of less than 1011 atoms/cm2 were measured from the TXRF analysis. The microroughness values for these films varied between 0.15 – 0.17 nm as measured by AFM. Low energy (500 eV) SIMS and NRA indicate high [N] near the top as well as throughout the bulk of the film, and a significant amount of [O] near the top of the film. High Resolution TEM pictures show a very uniform film with a physical thickness of 2.8 ± 0.1 nM, which yields an effective dielectric constant of 5.5, consistent with these types of oxynitride films.
Detection of Interfaces States Correlated with Layer-by-Layer Oxidation on Si(100)
Authors: Hattori T. , Nohira H. , Teramoto Y , Watanabe N.
Published: April 2011

The interface state densities near the midgap were measured with the progress of oxidation of atomically flat Si(100) surface. It was found that the interface state distribution in Si bandgap changes periodically with the progress of oxidation. Namely, the interface-state density near the midgap of Si exhibits drastic decrease at oxide film thickness where the surface roughness of oxide film takes its minimum value, while that does not exhibit decrease at the oxide film thickness where the surface roughness takes its maximum value. In order to minimize interface state densities the oxide film thickness should be precisely controlled to within an accuracy of 0.02 nm.
Quantum Confinement in Nanocrystalline Superlattices
Authors: Grom G. F. , Fauchet P. M. , Tsybeskov L. , Mccaffrey J. P. , Labbé H. J. , Lockwood D. J.
Published: April 2011

Photoconductance spectroscopy was used to probe the effects of quantum confinement in nanocrystalline (nc)-Si/amorphous (a)-SiO2 superlattices (SLs). A Metal-Oxide-Semiconductor (MOS)-like structure with the nc-Si SL incorporated in the oxide was fabricated to study charging/discharging processes in Si nanocrystals. The fine structure observed in photoconductance spectra at low temperatures was interpreted in terms of singularities in the carrier density of states, possibly due to energy quantization. In addition, a low-resistance sample exhibited photocurrent oscillations with a frequency of several kHz, which could be a manifestation of sequential resonant carrier tunneling in the nc-Si/a-SiO2 SL.
Memory Effects of Ion-Beam Synthesized Ge and Si Nanoclusters in Thin SiO2-Layers
Authors: Gebel T. , von Borany J. , Skorupa W. , Möller W. , Thees H.-J. , Wittmaack M. , Stegemann K.-H.
Published: April 2011

Nanocluster memories are promising for future non-volatile memory applications. In this work thin SiO2 films were implanted with Ge+ and Si+ and annealed subsequently. Charge storage effects of the MOS capacitors have been studied through I-V and high frequency C-V measurements. Positive voltage pulses lead to a positive flatband voltage shift of the C-V curve. Detrapping by applying negative voltage pulses leads to a negative shift. The achieved programming window using 6 V / 100 ms pulses for Ge based structures is higher than that for Si (2.0 V vs. 0.2 V). However the retention times for Si based memories are longer. For dedicated process parameters microstructural investigations (RBS, XTEM) of Ge+ implanted SiO2 layers showed two bands of clusters, one near the interface SiO2/Si and one in the center of the SiO2 layer.
Defect States Due to Silicon Dangling Bonds at the Si(100)/SiO2 Interface and the Passivation by Hydrogen Atoms
Authors: Kaneta C. , Yamasaki T. , Uchiyama T. , Uda T. , Terakura K.
Published: April 2011

The defect states due to the Si dangling-bonds at the Si(100)/SiO2 interface is investigated by employing the first-principles method based on the density functional theory. Two prototypes of the defects at the interface are considered. One exists on one end of a Si-Si dimer. On the other hand, the other exists on an edge of a Si-O-Si bridge. The electronic structures for these systems were calculated to investigate the interface states. For the former, two defect states strongly localizing on the silicon dangling bond at the interface appear in the band gap. The latter defect also generates two defect states. But the upper level is in the conduction band, while the lower level is in the band gap. It is also shown that the interface states completely disappear by introducing a H atom into the interface and terminating the dangling bonds. Our results suggest the silicon dangling-bond on a Si-Si dimer with no adjacent O atoms as a candidate for the Pb1 center.
Excess Vacancy Generation by Silicide Formation in Si
Authors: Jaccodine R. J.
Published: April 2011

It has been long recognized that excess point defects are generated when a metal silicide is formed on silicon. Since the common dopants diffuse in Si with the aid of both self-interstials and vacancies, these point defect perturbations will influence motion of diffusions that are in the adjacent vicinity. TiSi2 is known to enhance the concentration of vacancies and several mechanisms have been proposed for this effect. Recent literature has dealt with and rejected many of these ideas; however, some of the remaining few like film strain and lattice contraction upon silicidation have been the subject of state of the art experiments which has led to their rejection.

It is the contention of this paper that by using the experimental data from this recent work and reinterpreting it, the model of volume contraction of the silicides as the cause for vacancy injection, still represents the most physically satisfying cause and therefore, was mistakenly rejected.
Sequential Operation of Three Distinct Misfit Dislocation Introduction Mechanisms in an Epitaxial Bilayer Film
Authors: Gopal V. , Kvam E. P. , Chen E.-H. , Woodall J. M.
Published: April 2011

Mismatch stress relaxation mechanisms in bilayer films of (In, Al)As on InAs on GaP have been examined. Initial edge (90°) misfit dislocations at the InAs/GaP interface appear to be introduced directly at island edges during initial stages of growth. The incomplete mismatch compensation is taken up by later introduction of glissile (60°) dislocations, usually in pairs which combine to form edge dislocations. The edge dislocations in the interface then move laterally to equalize their spacings. The upper (In, Al)As capping layer, which is tensile strained to match the relaxed InAs, exhibits a different mechanism of misfit dislocation introduction. Threading dislocations move by climb, directly introducing sessile edge dislocations at the buried interface. It is believed this is the first time that this mechanism has been observed.
Stress Effects in the Oxidation of Planar SiO2 Thin Films
Authors: Delph T. J. , Jaccodine R. J.
Published: April 2011

We summarize here the results of recent experimental and analytical investigations into stress effects in planar SiO2 thin films. Experimentally, we examine the effects of a constant superposed in-plane stress upon the growth of thin oxide films in the 100 Å range. In contradiction to a widely accepted model of stress effects upon SiO2 film growth, we find that both compressive and tensile in-plane stresses tend to retard oxide growth by a roughly equal amount. Analytically, we investigate the effects of the small component of strain induced parallel to the oxidation interface by the large volume expansion inherent in the oxidation of silicon. Depending upon the circumstances, this strain component, dubbed the “intrinsic strain”, can have a non-negligible effect upon the growth of planar oxide layers.
Processing, Microstructure, and Fracture Behavior of Nickel/ Nickel Aluminide Multilayered Thin Films
Authors: Banerjee R. , Fain J. P. , Thompson G. B. , Anderson P. M. , Fraser H. L.
Published: April 2011

The Ni-Ni3Al system is the basis of a large number of Ni-based superalloys used extensively in the aerospace industry. The mechanical properties of bulk superalloys, which primarily consist of a Ni-based fcc matrix reinforced with cubic precipitates of Ni3Al, have been extensively researched. The goal of the present study is to investigate the mechanical properties of multilayered Ni / Ni3Al nanocomposites in the thin film form. These multilayers have been processed using UHV magnetron sputtering by alternate deposition of pure elemental Ni and Ni-25at%Al layers in the range of 20 nm – 120 nm. By varying the substrate material and processing parameters such as deposition temperature, multilayers with two types of interfacial orientations. (111) Ni //(111) Ni3Al and (002) Ni //(002) Ni3Al have been fabricated. Microstructural and phase characterization of the multilayers in both plan-view as well as cross-section geometries have been carried out using x-ray diffraction, SEM and TEM and the results of these will be discussed. Both orientations exhibited a high density of twins lying on the {111} planes. The loss of coherency in these multilayers as a function of the layer thickness will also be discussed. The cross-section fracture behavior of these multilayers has been studied by SEM fractography. Failure mode for fracture was a result of the application of tensile stresses. Interesting effects of the interfacial orientation and the layer thickness on the fracture surface of these multilayers will be discussed.
Fatigue of Thin Silver Films Investigated by Dynamic Microbeam Deflection
Authors: Schwaiger R. , Kraft O.
Published: April 2011

The fatigue behavior of bilayer microbeams consisting of thin Ag films on an SiO2 substrate was investigated. The beams were cyclically deflected using a commercial nanoindentation instrument, which is capable of precise positioning of indentations. The dynamic beam stiffness is monitored continuously throughout the whole experiment. Silver was chosen as a model material for fcc metals. For large strains and/or strain amplitudes the beam stiffness decreased significantly during the fatigue tests, which is related to damage formation, as cracks and extrusions were found after the experiment. In fatigue tests at lower strains and the same number of cycles no significant stiffness change was observed. In this case only extrusions but no cracks occurred.
Mechanical Properties and Adhesion of PZT Thin Films for MEMS
Authors: Jungk J. M. , Crozier B. T. , Bandyopadhyay A. , Moody N. R. , Bahr D. F.
Published: April 2011

Piezoelectric films are attractive materials for use in microelectromechanical systems (MEMS) due to their ability to act as both sensors and actuators. One of the primary modes of deformation is the deflection of lead zirconate titantate (PZT) beams and membranes, where the adhesion of the film is critical for the reliability of the device. Thin films of PZT between 250 and 750 nm have been grown via solution deposition routes onto platinized silicon substrates. The films have been tested using nanoindentation techniques. Two failure mechanism in these films have been observed Indentation induced delamination at the PZT-Pt interface occurs after the indenter tip is removed from the film when loads between 1 and 10 mN are applied to the sample, and at large loads (>75 mN) failure can be generated between the underlying oxide film and the silicon substrate while the tip is still engaged with the sample. Since each of these failure modes has a different mechanics solution, the results are compared to determine adhesion energy of the films. Fracture around the delaminated regions has been examined using scanning probe and electron microscopy. Freestanding PZT membranes above micromachined cavities have been mechanically deformed to examine the mechanical response and failure modes in these structures. The adhesion of the PZT improves with increased percent crystallization due to the introduction of residual tensile stresses. Processing, mechanical properties, and failure modes in these devices will be discussed.
Thermal Shock Behaviour of Thin Bi-Material Ceramic Systems
Authors: Busso E. P. , Tkach Y. V. , Travis R. P.
Published: April 2011

This work describes a methodology developed to predict the thermal shock behaviour of thin bi-material ceramic systems. An experimental procedure based on controlled air cooling has been devised to simulate the flow of a gas stream over the surface of a thin two-layer ceramic system. Results of microstructural and fractographic investigations conducted on tested samples, including representative fracture patterns and crack initiation sites, are presented. A probabilistic-deterministic approach to predict the thermal shock behaviour of bi-material ceramic systems is proposed. Failure diagrams are constructed from a combination of the experimental and analytical studies. Critical thermal transient conditions typical of start-up and shut-down operation in solid oxide fuel cell are determined.
Mechanical Behavior of Indium Oxide Thin Films on Polymer Substrates
Authors: Cairns D. R. , Sachsman S. M. , Sparacin D. K. , Witte R. P. , Crawford G. P. , Paine D. C.
Published: April 2011

We report on the change in electrical resistance of tin doped indium oxide thin films on polymer substrates with increasing uniaxial strain. The resistance increases rapidly but continuously above a threshold strain. The threshold strain at which the resistance increases is correlated to the onset of cracking in the oxide film. The strain for cracking and increase in resistance depend upon film thickness. We have measured the distance between neighboring ITO cracks as a function of strain in situ using an optical microscope. At high uniaxial strains the ITO layer fails in the orthogonal direction due to lateral contraction of the polymer substrate. The gradual increase in resistance is modeled assuming there is a conducting layer at the polymer/ITO interface.
Study of Crack Propagation at an Oxide/Polymer Interface Under Varying Loading Conditions
Authors: Panteliidis Dtmitrios , Snodgrass Jeffrey , Dauskardt Reinhold H. , Bravman John C.
Published: April 2011

We investigate the effect of loading conditions and process parameters on the failure mode of a Silicon/SiO2/Silane/BCB interface system. Chemical analysis of the fracture surfaces with XPS reveals different crack paths through the structure for the two different loading configurations studied. Furthermore, the curing temperature of the silane coupling agent is shown to have a profound impact on the subcritical debond behavior of the structure. A mechanism responsible for this effect is identified and the XPS data is directly correlated to quantitative information about the resistance of the structure to fracture and subcritical crack growth.
Stress Development in Low Dielectric Constant Silica Films During Drying and Heating Process
Authors: Lu Mengcheng , Brinker C. Jeffrey
Published: April 2011

Low dielectric constant silica films are made using a surfactant templated sol-gel process (K∼2.5) or an ambient temperature and pressure aerogel process (K∼1.5). This paper will present the in-situ measurement and analysis of stress development during the making of these films, from the onset of drying till the end of heating. The drying stress is measured by a cantilever beam technique; the thermal stress is measured by monitoring the wafer curvature using a laser deflection method. During the course of drying, the surfactant templated films experience a low drying stress due to the influence of the surfactant on surface tension and extent of siloxane condensation. The aerogel films first develop a biaxial tensile stress due to solidification and initial drying. At the final stage of drying where the drying stress vanishes, dilation of the film recreates the porosity of the wet gel state, reducing the residual stress to zero. For the surfactant templated films, very small residual tensile stress remains after the heat treatment is finished (∼30MPa). Aerogel film has almost no measurable stress developed in the calcination process. In situ spectroscopic ellipsometry analysis during drying and heating, and TGA/DTA are all used to help understand the stress development.
Measurement of Local Strain in Thin Aluminium Interconnects Using Convergent Beam Electron Diffraction (CBED)
Authors: Krämer S. , Mayer J.
Published: April 2011

Energy filtered convergent beam electron diffraction (CBED) was used to investigate localized strain in aluminium interconnects. An analysis of the higher order Laue zone (HOLZ) line positions in CBED patterns makes it possible to measure the lattice strain with high accuracy (∼10−4) and high spatial resolution (10 to 100 nm). The strain development in a single grain was measured during thermal cycling between −170°C and + 100°C. The grain showed reversible, elastic behaviour over the whole temperature range building up large strains at low temperatures. By comparing with finite element simulations, a detailed understanding of the tri-axial strain state could be achieved.
Plastic and Elastic Behavior of Sputtered Bilayered Films by Nanoindedtation
Authors: Kikuchi N. , Kusano E. , Sawahira Y. , Kinbara A.
Published: April 2011

Deformation behavior of sputtered Al/TiN and Cu/TiN bilayered films was examined by using dissipated and elastic energies estimated from the area enclosed by the load-displacement curve of nanoindentation. These films studied consisted of TiN top-layer of 500 nm and Al or Cu underlayer of 0 - 500 nm on glass or sapphire substrate. The dissipated energy for plastic deformation increased with increasing thickness of metal underlayer, while the elastic energy remained constant. A decrease in plastic energy was observed by changing the underlayer material from Al to Cu. Further, a reduction in elastic energy was observed when a sapphire was used as a substrate. Experimental results show that the plastic deformation mainly occurred in metal underlayer and the elastic deformation did in TiN layer and in the substrate. It was concluded that the yield stress and elastic modulus of layers and substrate strongly affect the deformation behavior of the films.
Mechanical Properties of Electroplated Copper Thin Films
Authors: Spolenak R. , Volkert C. A. , Takahashi K. , Fiorillo S. , Miner J. , Brown W. L.
Published: April 2011

It is well known that the mechanical properties of thin films depend critically on film thickness However, the contributions from film thickness and grain size are difficult to separate, because they typically scale with each other. In one study by Venkatraman and Bravman, Al films, which were thinned using anodic oxidation to reduce film thickness without changing grain size, showed a clear increase in yield stress with decreasing film thickness.

We have performed a similar study on both electroplated and sputtered Cu films by using chemical-mechanical polishing (CMP) to reduce the film thickness without changing the grain size. Stress-temperature curves were measured for both the electroplated and sputtered Cu films with thicknesses between 0.1 and 1.8 microns using a laser scanning wafer curvature technique. The yield stress at room temperature was found to increase with decreasing film thickness for both sets of samples. The sputtered films, however, showed higher yield stresses in comparison to the electroplated films. Most of these differences can be attributed to the different microstructures of the films, which were determined by focused ion beam (FIB) microscopy and x-ray diffraction.
Hall-Petch Hardening in Pulsed Laser Deposited Nickel and Copper Thin Films
Authors: Knapp J. A. , Follstaedt D. M. , Banks J. C. , Myers S. M.
Published: April 2011

Very fine-grained Ni and Cu films were formed using pulsed laser deposition onto fused silica substrates. The grain sizes in the films were characterized by electron microscopy, and the mechanical properties were determined by ultra-low load indentation, with finite-element modeling used to evaluate the properties of the layers separately from those of the substrate. Some Ni films were also examined after annealing to 350 and 450°C to enlarge the grain sizes. These preliminary results show that the observed hardnesses are consistent with a simple extension of the Hall-Petch relationship to grain sizes as small as 11 nm for Ni and 32 nm for Cu.
The Microstructure and Nanoindentation Behaviour of TiN/NbN Multilayers
Authors: Molina-Aldareguia J. M. , Lloyd S. J. , Barber Z. H. , Blamire M. G. , Clegg W. J.
Published: April 2011

TiN/NbN multilayers and TiN monolithic films have been grown by UHV reactive magnetron sputter deposition on MgO single crystals. The hardness has been measured by nanoindentation and the as-deposited and deformed structures studied in cross-section using transmission electron microscopy. It has been found that initially the multilayers grow epitaxially with the substrate. However, once the overall film thickness has reached ∼300 nm, epitaxial growth ceases. No increase in hardness with respect to monolithic films of the multilayer components is observed in these multilayers. Experiments on monolithic films of TiN show that the same loss of epitaxy occurs, leading to a reduction in the hardness of the films, and that this change in growth morphology is triggered by the internal stresses induced within the films during deposition.
Pt Film Growth with Tetra-Kis(Triflurophosphine)Platinum
Authors: Sun Y.-M. , Lozano J. , Mettlach N. , Ekerdt J. G. , Madhukar S. , Hance R. L. , White J. M.
Published: April 2011

Platinum film growth using Pt(PF3)4 precursors was investigated. The study focused on three aspects of film growth: conformality, adhesion and selective growth. Pt(PF3)4 deposited pure Pt films over a wide range of temperatures (∼200 to 400 °C). At 200 °C, the step coverage for a via with an aspect ratio of three was poor. Lower growth temperatures showed a significant decrease in the growth rate. In addition, these films had poor adhesion to the substrate as indicated by separation between the Pt and the substrate in cross sectional scanning electron microscopy images. Oxygen addition during Pt film growth from Pt(PF3)4 improved both film conformality and adhesion. With oxygen, the step coverage on the side wall was greater than 90 % The dependence of the film growth rate on oxygen varied with the growth temperature: the growth rate decreased at 200 °C, while it changed slightly at 260 °C when oxygen was added. The substrate effect on the initial growth rate was studied on various substrates. The initial growth rate on metals is much faster than that on other substrates. The growth rate decreased on various substrates in the order of iridium > titanium nitride > barium strontium titanate > silicon nitride > silicon oxide.
Integration Issues of (Ba,Sr)TiO3Thin Films in High Density Devices
Authors: Yoo C. Y. , Park H. B. , Hwang D. S. , Hideki H. , Kim W. D. , Lim H. J. , Lee B. T. , Park Y. W. , Lee S. I. , Lee M. Y.
Published: April 2011

Recent progress to overcome integration issues related with (Ba,Sr)TiO3 films are presented. Firstly, ternary barrier material, Ti0.7Al0.3N deposited by reactive sputtering is shown to have superior oxidation resistance than TiN through the test using contact string pattern where Pt is deposited as a electrode. Ti0.7Al0.3N barrier is able to keep stable contact resistance below 100Ω even under oxidizing condition where the temperature is 550°C and oxygen partial pressure is 7.6 Torr. If rapid thermal annealing is used, annealing temperature without oxidation of Ti0.7Al0.3N can be increased by about 100°C. Ti0.7Al0.3N is thought to be the promising one which can endure during post-annealing process. Secondly, electroplating technology is employed to fabricate the stack capacitor of Pt that has been known to be very difficult to etch. 500Å-thick Pt is used as a seed layer and very thick Pt is selectively grown on the seed layer by the electroplating. The Pt height can be controlled by changing the electroplating time, so we can make stack Pt over 8000Å. Thirdly, low temperature deposition process for MOCVD BST film is developed. The equivalent oxide thickness of about 3.5Å is obtained on Pt electrode when BST thickness is 150Å. BST film is deposited at 420°C and annealed at 700°C under oxidizing atmosphere. It is suggested that a new two step annealing consisting of high temperature annealing under inert atmosphere and low temperature annealing under oxidizing atmosphere is very effective to achieve the high dielectric constant and low leakage current of BST films at the same time. It is also adequate for preventing the barrier oxidation. BST film with Toxeq. of 5.2Å and low leakage current is obtained by annealing at 650°C under N2 followed by annealing at 550TC under O2. Electrical properties of BST deposited on side-wall of Pt concave capacitor is evaluated. The concave capacitor with about aspect ratio 3 shows the same capacitance and leakage current as the planar capacitor, which implies that BST composition and thickness is uniform on the side-wall. It is concluded that BST films on Pt electrode can be applied to real device.
MOCVD of Nb Substituted SrBi2Ta2O9 for Integrated Ferroelectric Capacitors
Authors: Hendrix B. C. , Glassman T. E. , Roeder J. F.
Published: April 2011

The Bi layered perovskites are promising materials for ferroelectric random access memories (FeRAM's) because of their inherently high resistance to fatigue. Liquid delivery, flash vaporization metalorganic chemical vapor deposition (LD-MOCVD) is an attractive process for these materials, because it offers the ability to produce high quality, conformal films of controlled composition for both high and low density memory applications. We have developed a well-controlled process to deposit Nb-substituted SrBi2Ta2O9 (SBNT) using a mixed alkoxide-β-diketonate precursor Nb(O-i-Pr)4(thd) that is compatible with a previously developed precursor suite for SBT (Sr(thd)2-pmdeta, Bi(thd)3, and Ta(O-i-Pr)4(thd)). The Nb and Ta precursors behave in the same way in the process, making the Nb substitution level in the film identical to that in the precursor solution. In this study, wavelength dispersive x-ray fluorescence has been used to characterize composition and thickness. As-deposited films are smooth, with a surface roughness of 2 nm RMS. After a post-deposition annealing treatment, a high quality layered perovskite crystal structure was obtained. The resultant ferroelectric hysteresis shows a 50% increase in coercive voltage for 28% Nb substitution at the Ta site with the same switchable polarization. In the 28% Nb containing film, imprint was significantly improved compared to SBT films without substitution.
Effect of Film Composition on Low Temperature Processing of SBT Deposited by MOCVD
Authors: Bachhofer Harald , Hintermaier Frank , Hauf Manfred , Spindler Oswald , Haneder Thomas , Dehm Christine , von Philipsborn Henning , Waser Rainer
Published: April 2011

Bi-layered ferroelectric strontium bismuth tantalate (SBT) thin films of various film compositions were deposited on Pt/Ti/SiO2/Si substrates by metalorganic chemical vapor deposition (MOCVD) and crystallized at 700°C in oxygen ambient. Phase transition, orientation, second phases and remanent polarization were investigated with respect to film stoichiometry. X-ray diffraction (XRD) measurements revealed that excess Bi lowers the transition temperature from fluorite-type to ferroelectric phase. However, SBT films with Bi-excess of 15% or higher exhibit pronounced Bi-loss during crystallization and a decrease in the relative intensity of the (200) peak. Highly Sr-deficient films are not fully crystallized but support pyrochlore formation. The maximum remanent polarization is obtained at a Sr-deficiency of 15–25% and a Bi-excess of 10% (0.85/2.20/2.00).
Preparation of a New SrBi2Ta2O9 (SBT) Chemical Solution Using Crown Ether and its Thin Film Deposition
Authors: Min Yo-Sep , Lee June Key , Lee In-Sook
Published: April 2011

A new chemical solution for the deposition of SrBi2Ta2O9 (SBT) thin films using crown ether is proposed. Crown ether enhances the solubility of bismuth acetate in acetic acid, which makes a solvent solution possible. A metal acetate-based SBT precursor solution was prepared in acetic acid using 18-crown-6, strontium acetate, bismuth acetate and tantalum ethoxide. (115)-preferentially oriented ferroelectric SBT thin films were formed on Pt/TiO2/SiO2/Si substrates by spin-coating with the new solution. After post-annealing at 800°C, a hysteresis loop obtained from a 2000Å thick SBT film with Pt electrodes showed a remanent polarization of ∼3μC/cm2 and a coercive voltage of ∼50kV/cm. It was shown from SIMS depth profiles that excess bismuth atoms in the SBT thin film diffused towards the Pt electrodes during post-annealing.
A Study on the Selective Nucleations for Formation of Large Single Grains in PZT Thin Films
Authors: Lee Jang-Sik , Park Eung-Chul , Park Jung-Ho , Lee Byung-Il , Joo Seung-Ki
Published: April 2011

Selective nucleation and lateral growing method have been developed for high quality ferroelectric PZT(65/35) thin films using perovskite-phase PZT island seed. The PZT films on PZT seed island were transformed into the perovskite phase at temperatures as low as 540°C, which is 150°C lower than compared to that of PZT thin films deposited on Pt films. The temperature difference enables lateral growth without undesirable random nucleation. Maximum grain sizes of the perovskite-phase PZT films were determined by the annealing temperature. The PZT thin films show a leakage current density of 8×10−8 A/cm2, breakdown field of 1240 kV/cm, saturation polarization of 42 μC/cm2, and remanent polarization of 30 μC/cm2, whose values were maintained up to 2×1011 cycles. In this study, we show that when there was no grain boundary in the area measured, degradation such as fatigue and retention was not observed even with Pt electrodes. So the main source of degradation is the grain boundary in the PZT thin films.
Thickness Dependence and Electrical Properties of Ultrathin PZT Films Grown on SrRuO3/SrTiO3 by MOCVD
Authors: Shimizu M. , Fujisawa H. , Niu H.
Published: April 2011

Epitaxial Pb(Zr,Ti)O3 (PZT) thin films with various thicknesses ranging from 40 to 400nm were prepared on SrRuO3/SrTiO3 by metalorganic chemical vapor deposition (MOCVD). The dependence of lattice constant on the film thickness and temperature was examined. The PZT films obtained showed ferroelectric hysteresis loops even when film thickness was 40nm. Applied voltage for obtaining high polarization density decreased as film thickness decreased. The 40nm-thick PZT film had the polarization density (Pr) of 38mC/cm2 at an applied voltage (Vc) of 0.7V.
Observations of Domain Structure at Initial Growth Stage of PbTiO3 Thin Films Grown by Mocvd
Authors: Fujisawa H. , Shimizu M. , Niu H. , Honda K. , Ohtani S
Published: April 2011

Domain structure and growth mechanism of PbTiO3 thin films were investigated using a transmission electron microscopy(TEM) from the viewpoint of size effects. At initial growth stage of (111)-oriented PbTiO3 films prepared by metalorganic chemical vapor deposition(MOCVD), triangle-shaped islands were grown on Pt(111)/SiO2/Si before becoming a continuous film. Triangular islands grew gradually in a lateral dimension. This means that PbTiO3 films grew two-dimensionally at initial growth stage. In cross-sectional TEM photomicrographs, (101)-twin boundaries (90° domain walls) and inclination of {110} or {101}-plane were observed in PbTiO3 islands. This result indicates that such small PbTiO3 islands have a tetragonal structure and could have spontaneous polarization. The minimum island which had 90° domain walls was 10nm high and 18nm wide.
Near-Field Second Harmonic Microscopy of Thin Ferroelectric Films
Authors: Smolyaninov I. I. , Liang H. Y. , Lee C. H. , Davis C. C. , Rotter L. D. , Kaiser D. L.
Published: April 2011

Near-field second harmonic microscopy is ideally suited for studies of local nonlinearity and poling of ferroelectric materials at the microscopic level. Its main advantages in comparison with other scanning probe techniques are the possibility of fast time-resolved measurements, and substantially smaller perturbation of the sample under investigation caused by the optical probe. We report second harmonic imaging of the surface of thin BaTiO3 films obtained in a near-field microscopy setup using a Ti:sapphire laser system consisting of an oscillator and a regenerative amplifier operating at 810 nm. Optical resolution on the order of 80 nm has been achieved.
Effect of TiN Treated by Rapid Thermal Annealing on Properties of BST Capacitors Prepared by RF Magnetron Co-sputter System at Low Substrate Temperature
Authors: Teng T. H. , Hwang C. C. , Lai M. J. , Huang S. C. , Chen J. S. , Jaing C. C. , Cheng H. C.
Published: April 2011

In this work, (Ba0.7Sr0.3)TiO3 thin films on Pt/TiN/Ti/Si substrate were deposited by an
RF magnetron co-sputter system at 300°C in an Ar+O2 mixed ambient. In the integration of BST capacitors, the diffusion barrier (TiN) under bottom electrodes is one of the key issues. To obtain a stable and excellent diffusion barrier against inter-diffusion between Pt and Si, as well
as against being oxidized during BST deposition, TiN was treated by a rapid thermal annealing (RTA) process. Experimental results indicated that proper RTA treatments resulted in a superior TiN barrier layer. In addition, low substrate temperature during BST deposition suppressed the phenomena of inter-diffusion and barrier oxidation. Furthermore, Pt hillocking, another problem during BST deposition because of high thermal budget, was also solved by
reducing substrate temperature during BST deposition. The MIM (Pt/BST/Pt) structure was used in the experiments for electrical properties measurement. High dielectric constant (εr =300), low leakage current (l.5×10−8 A/cm2) under 0.1MV/cm, and 10 year lifetime under 1.6MV/cm were achieved with an Ar+O2 mixed ambient at a low substrate temperature (300°C).
Densification and Evolution of Stress Development in Solution Derived PbZr0.53Ti0.47O3 Thin Layers
Authors: Park Sang M.
Published: April 2011

Stress development in thin layers of PbZr0.53Ti0.47O3 (PZT) and PbTiO3 (PT) prepared by sol-gel processing was monitored by in situ laser reflectance measurements. Layers were spin coated onto silicon substrates and thermally cycled to 600°C and 650°C. The shrinkage normal to the film plane was determined by in situ ellipsometry and scanning electron microscopy. Both PZT and PT multilayers showed a similar stress behavior on heating, but quite different behavior on cooling. As the film became dense at high temperatures, total stress was dominated by the thermal expansion mismatch between the oxide layer and the substrate. On cooling, the PT multilayers, which already crystallized into the perovskite structure, ended nearly stress free at room temperature, whereas mostly amorphous PZT multilayers were under a high tensile stress. Densification in PZT layers appeared to occur between 370°C and 520°C. At near 370°C the shrinkage mode for a single PZT layer was also observed to change substantially. A two-stage sintering process employing 450°C-sintering and 650°C-crystallization was found to be as effective as direct furnace insertion method in producing a dense film.
Oxygen Deficiency and Vacancy Formation in LSCO/PLZT/LSCO Capacitors
Authors: Friessnegg T. , Nielsen B. , Ghosha V. J. , Aggarwal S. , Keeble D. J. , Poindexter E. H. , Ramesh R.
Published: April 2011

Vacancy type defects in La0.5 Sr0.5CoO3/Pb0.9La0.1Zr0.2 Ti0.8/La0.5Sr0.5CoO3 capacitors were investigated by positron depth profiling. Post-growth annealing of the capacitor structure in oxygen deficient atmosphere exhibits the formation of vacancy type defects in all layers. A significant increase in open volume defects was found in the top and bottom electrode. The changes in the bottom electrode were studied more closely by etching off the top layer.
Integrated Thin Film Capacitor Arrays Utilizing Sol-Gel Derived Ferroelectrics
Authors: Liu David , Makl Steve , Heistand Robert H.
Published: April 2011

Niobium-doped lead zircomate titanate (PNZT) thin film dielectric material has been produced on a large scale using a thick-coating sol-gel process. The material has been applied to the fabrication of commercial integrated capacitor array devices. Compared to conventional processes, this low-cost, long-shelf-life procedure had at least a 4-fold processing time enhancement. The specific capacitance of 2500 nF/cm2 and integrated density of over 200 component/cm2 have been demonstrated. The frequency domain capacitance measurement of integrated PNZT capacitors exhibits a frequency-independent behavior up to 2 GHz when a DC bias is applied. Leakage-voltage dependence follows the space-charge-limited-current (SCLC) mechanism. The fabricated integrated capacitor arrays pass the industrial standard of reliability for discrete multilayer capacitors.
Coplanar Capacitors with High Dielectric Constant BaSrTiO3 for Microwave Application
Authors: Hu Wei , Fuflyigin Vladimir , Chi Jim
Published: April 2011

A coplanar structure is shown to be free of the asymmetrical I-V characteristics normally observed in MIM capacitors with BST inter-electrode dielectric. The low barrier height at the bottom interface is found to be responsible for the asymmetry, which causes increased leakage current and reduced breakdown voltage in one bias polarity. These problems can be eliminated using a coplanar structure, which has been shown elsewhere to have a very low parasitic inductance and a very high resonant frequency. However, these improvements are realized at the cost of a four times reduction of capacitance per unit area.
Ferroelectric Properties of II-VI Type Semiconducting Thin Films on Si(100)
Authors: Hotta Y. , Tabata H. , Kawai T.
Published: April 2011

We have demonstrated the presence of ferroelectric properties in non-oxide (II-VI type semiconductor) ferroelectric thin films, such as (Zn,Cd)Te, (Zn,Cd)Se and (Zn,Cd)S (thickness: 3000–5000 Å). They have shown the ferroelectric hysteresis feature with memory windows of 0.2V, 0.3V and 0.8V, respectively. The materials design for getting the ferroelectric nature is as follows: when the size of the replaced atom is smaller than the host atom, then the substituent atoms can occupy off-centered positions, thus locally induce electric dipoles, thereby leading to ferroelectric behavior. These II-VI wide gap semiconducting ferroelectric films will open the door for new memory devices.
Dielectric and Transverse Piezoelectric Characterization of Sol-Gel Derived Pb(Mg1/3Nb2/3)O3-PbTiO3 (70/30) FILMS WITH {100} and {111} Textures
Authors: Park Jeong Hwan , Trolier-McKinstry Susan
Published: April 2011

Highly {100} and {111} oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 (70/30) films were deposited on Pt(111)-passivated silicon substrates using a modified sol-gel process. In both cases, the degree of preferred orientation did not change with film thickness from 0.56 μm to 1.5 μm. The room temperature dielectric constants for the {100}-oriented films were 2100–2650, while those for the {111} oriented films were 1900–2350. In both cases tan δ was less than 0.03. It was found that the piezoelectric coefficient (d31) of the PMN-PT films increased with increasing film thickness. The d31 coefficient of highly {100} oriented PMN-PT films poled for 5 minutes at 85 kV/cm were found to range from –45 to –86 pC/N assuming a Young's modulus of 35 GPa. Highly {100} oriented PMN-PT films showed larger piezoelectric coefficients than {111} oriented films. Results on aging of the piezoelectric coefficients for the differently oriented films are also presented.
Preparation of Piezoelectric PZT Thin Films by Mocvd for MEMS Applications
Authors: Chen Ing-Shin , Kim Dong-Joo , Maria Jon-Paul , Roeder Jeffery F. , Kingon Angus I.
Published: April 2011

Integration of piezoelectric Pb(Zr,Ti)O3 (PZT) thin films promises to provide silicon-based microelectromechanical systems (MEMS) with added functionality. PZT films with compositions near the tetragonal/rhombohedral morphotropic boundary have been deposited on iridium-coated Si substrates by a thermal chemical vapor deposition (CVD) process using flash vaporized metalorganic precursors. Process variables including (A-site)-to-(B-site) ratios in the precursor mix and deposition times have been surveyed. Stoichiometric, perovskite films with nominal Zr/Ti ratios ranging from 40/60 to 60/40 were obtained. Parallel-plate capacitor structures have been fabricated by depositing Pt top electrodes using e-beam evaporation through shadow masks. Ferroelectric hysteresis loops were measured using a standard ferroelectric tester. Remenant polarization values in the range of 20∼30 μC/cm2 were obtained. For films of 0.5 μm or thicker, piezoelectric hysteresis loops were characterized by dual-beam interferometry. Longitudinal piezoelectric coefficients (d33) of 30∼60 pm/V were observed on the films deposited between 550 and 600°C.
(001)-Oriented LaNiO3 Bottom Electrodes and (001)-Textured Ferroelectric Thin Films on LaNiO3
Authors: Zhang Zhenshan , Park Jeong Hwan , Trolier-McKinstry Susan
Published: April 2011

In this work, highly (001)pc-oriented thin films of LaNiO3 (LNO) were deposited by DC magnetron sputtering onto Si substrates (pc = pseudocubic indices). The target powder was prepared using a molten salt technique with Na2CO3 as a flux. The final target density was greater than 85% of theoretical density. The best results were obtained when sputtering was carried out at a power of 186 W and a working pressure of 45 mtorr with a gas composition of 50% O2 + 50% Ar. The thickness of the deposited films was proportional to the sputtering time, and the growth rate was 300Å/hour. Highly (001)-oriented thin films of lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (PZT) and Pb[(Mg1/3Nb2/3)0.7Ti0.3]O3 (PMN-PT) were fabricated by a sol-gel method on (001)-textured LNO metallic oxide electrodes. A remanent polarization of 12 μC/cm2 and d31 of -125 pC/N (assuming a Young's modulus of 35 GPa) were measured on the PMN-PT thin films with a thickness of 0.9 μm. This piezoelectric coefficient considerably exceeds that available from PZT films, and depends critically on the film orientation. Changes in the hysteresis loop due to externally applied stress will also be described.
High Density Dry Etching of (Ba,Sr)TiO3 and LaNiO3
Authors: Lee K. P. , Jung K. B. , Srivastava A , Kumar D. , Singh R. K. , Pearton S. J.
Published: April 2011

High density plasma etching of (Ba,Sr)TiO3 (BST) and LaNiO3 (LNO) thin films was performed in two different plasma chemistries, Cl2/Ar and CH4/H2/Ar. While the latter chemistry produced extremely low etch rates (≤ 100 Å-min−1) under all conditions, the Cl2/Ar produced a smooth anisotropic pattern transfer. The etching was still strongly ion-assisted, but maximum removal rates of ∼900 Å min−1 for both materials were achieved with selectivities of ∼16 for BST and ∼7 for LNO over Si. A single layer of thick (∼7 μm) photoresist is an effective mask under these conditions.
Narrow Resonance Profiling Study of the Oxidation of Ti1-xALxN Barrier Layer
Authors: Hugon M. C. , Desvignes J. M. , Letendu F. , Agius B. , Vickridge I , Kim D. J. , Ayguavives F. , Kingon A. I.
Published: April 2011

The preparation of ferroelectric and high dielectric perovskite materials, which is performed at high temperature (550–750°C) in oxidizing environments, provides strong limitations on the choice of electrode materials which have to be used for integration with semiconductor devices. To minimize interdiffusion and oxidation reactions, a diffusion barrier must be placed between Si substrate and electrode material (Pt, lrO2, RuO2.…). Ti1-xAlxN thin films, deposited by reactive sputtering, are promising materials as electrically conductive layers and robust diffusion barriers. The stability of these films has been investigated at conditions typically used for crystallization of perovskite dielectrics. Films with various Al composition (x=0, 0.1, 0.2 and 0.4) have therefore been annealed by RTA (rapid thermal annealing) in 18O2 at 550–750°C. The concentration depth profiles of both 18O and 27A1 were measured before and after the RTA treatments via the narrow resonances of 18O(p,α)15N at 151 keV (fwhm=100 eV) and 27Al(p,γ)28Si at 992 keV (fwhm=100 eV). Al incorporation in the films reduces oxide growth especially at high annealing temperatures. The Al excitation curves indicate a uniform Al content for as deposited Ti1−xAlxN, and reveal Al diffusion to the surface during oxidation which indicates the formation of an Al rich oxide layer at the Ti1-xAlxN surface.
From Ferroelectrics to Polymers - Perspectives for Thin Film Optical Waveguides and Devices
Authors: Buchal Christoph
Published: April 2011

Presently commercial optical fiber links experience an explosive growth. On the other hand, the integration of optical functions on a single substrate (“Integrated Optical Device”) is still mostly limited to the R & D-laboratories. Only Mach-Zehnder modulators, made from ferroelectric crystals, have found commercial applications so far. The development phase of the integrated optical devices, based on bulk crystalline LiNbO3, is now covering a time span of nearly 30 years. In comparison, the development of the thin film growth of optical oxide ferroelectrics or of tailored optical polymers is just a few years old and we are still at the beginning of the learning curve.
Luminescence Efficiency of Erbium-Doped BaTiO3 Thin Films
Authors: Teren A. R. , Wessels B. W.
Published: April 2011

The factors limiting the efficiency of Er3+ luminescence at 1.54 μm (0.8 eV) in erbiumdoped barium titanate films were studied. To investigate the effect of film stoichiometry on luminescence efficiency films were annealed in oxygen and in vacuum. For films annealed in oxygen at temperatures of 700–900°C a nominal increase in the luminescence efficiency was observed. Vacuum annealing resulted in strong quenching of the emission intensity. Transient photoluminesence measurements showed that the emission lifetime also decreased for the reduced films. This effect was reversible; upon oxygen annealing both the emission intensity and lifetime were restored to their original values. These results indicate that the Er3+ luminescence efficiency strongly depends on film stoichiometry.