The hillock growth mechanism at the surface of Pt/TiN electrodes is investigated. TEM and SEM observations confirm that local delamination occurs at the Pt/TiN interface first, and then, plastic deformation of the Pt films under compressive stress forms hollow domes, which result in hillocks. Hillocks always start to grow when the internal stress in the Pt films reaches about −1000 MPa during annealing in N2/O2 ambient. Since the initial internal stress of Pt thin films varies from −500 to 500 MPa, depending on their deposition temperature, the hillock growth temperature strongly depends on the deposition temperature of the Pt films. It is very important, therefore, to control the initial internal stress in Pt films in order to eliminate hillock growth at the surface of Pt/TiN electrodes.

We describe how the inhibitory effect of ambient oxygen on suicide formation may be exploited in designing noble metal electrode structures suitable for perovskite-based memory devices. Reactions of Pt and Ir films with substrates of silicon and tungsten suicide (WSi2.8/Si) were examined after anneals in atmospheric pressure ambients of oxygen or nitrogen al temperatures of 640 °C for various initial noble metal film thicknesses. Metal/silicon reactions and phase formation were studied by Rutherford Backscattering Spectroscopy, X-ray diffraction. and electrical resistance measurements. While annealing in nitrogen resulted in complete noble metal silicidation in the all samples, some Pt and most to all of the Ir remained after equivalent anneals in oxygen. Oxygen exhibited a greater inhibitory effect on silicidation in thin Ir samples, where no suicide formation was observed. The consistent presence of unreacted noble metal M after oxygen annealing is attributed to the formation of an oxygen-containing M-O-Si barrier which interferes with the silicidation reaction. Qualitative through-film resistance measurements indicate that these in-situ formed M-O-Si barrier layers can be at least moderately conductive, a prerequisite for their possible use as a replacement for deposited barrier materials.

SrBi2Ta2O9 has attracted great interest for non-volatile memory applications due to its minimal polarization fatigue. This paper describes systematic studies, using pulsed laser deposition, on the effect of deposition conditions on the Bi-Pt reaction and on the potential for low temperature processing. Changing the deposition temperature (Ts) and oxygen gas pressure during deposition can control the Bi content in the films. At a Ts of 600°C, the films have excess Bi and do not fully crystallize to SBT, resulting in poor remnant polarization (Pr). These films consist mostly of the pyrochlore phase, plus a small amount of disordered, c-oriented layered perovskite SBT. By annealing over 750°C, the films show improved Pr, but further Pt - Bi interactions occur. At a Ts of 700°C, the as-deposited films are fully crystallized and show saturated hysteresis loops. However, Bi deficiency through alloying results in reduced remnant polarization (2Pr = 7.0μC/cm2). Films on Ir/Pt show reduced electrode reactions and improved properties.

The effect of bottom electrode thickness on the electrical properties of PZT capacitors with Ir and IrO2, electrodes was investigated, with particular attention to switching endurance characteristics. Ir and IrO2 electrodes were prepared by rf magnetron sputtering. PZT films were grown by MOCVD. Secondary ion mass spectrometry (SIMS) analysis showed thick Ir and IrO2 electrodes performed well as a barrier to the PZT elements. On the other hand, strong diffusion at the interface between PZT and the electrodes was observed, when the Ir and IrO2 electrodes were thin. From transmission electron microscope (TEM) observation, it was also found that there was an amorphous intermediate layer at the interface between the PZT and the thick Ir bottom electrode. The switching endurance characteristics were influenced by the thickness of the Ir bottom electrode.

The dielectric constant and dispersion of sputtered barium strontium titanate (BST) thin films deposited on Ir electrodes have been measured as a function of frequency and dielectric film thickness. Based on the measured variation in capacitance density with BST film thickness, an interfacial capacitance and thin film capacitance have been extracted. The variation of the interfacial capacitance density and the thin film capacitance density with frequency indicates that the majority of dispersion measured for BST deposited on Ir electrodes is due to the interfacial capacitance, in contrast to results found for Pt electrodes [1]. The temperature dependence of the interfacial capacitance and thin film capacitance has also been measured for these electrodes.

Epitaxial 0%, 3% and 10% La doped PZT capacitors with a LSCO bottom electrode grown by pulsed laser deposition on Si using a Ti(Al)N/Pt conducting barrier layer were systematically studied. Ferroelectric capacitors substituted with 10% La show a significantly lower coercive voltage compared to capacitors with 0% and 3% La. This is attributed to the systematic variation of the domain structure of the PLZT film with the increase of La concentration. The in-plane orientation relationship of this heterostructure is: [110]PLZT/[110]LSCO/[110]Pt/[110]Ti(AI)N[110]si. The morphology of the domains as a function of La concentration was studied using high resolution transmission electron microscopy(HREM). The Pt/Ti(Al)N conducting barrier layer stack is intact after the deposition of the LSCO/PLZT/LSCO stack. All Ti(Al)N layers in the samples studied consist of column-like structures with a [110] texture.

A wet-chemical process for depositing and patterning RuO2 contacts for use in ferroelectric thin film capacitive devices is described. Three new ruthenium compounds containing photocrosslinkable organic groups have been synthesized which polymerize upon UV exposure. Preliminary pattern forming ability of the new precursors has been tested with the use of a simple straight line contact mask. The exposed portions of the precursor films are resistant to ethanol, acetone, and light abrasion. The formation of crystalline RuO2 upon organic pyrolysis was confirmed by x-ray diffraction. Synthesized ruthenium complexes were compared to commercially available ruthenium acetylacetonate. The synthesized organo-ruthenium complexes showed improvement in pattern resolution and clarity.

In this study, we investigated the effects of the addition of CF4, Cl2, and N2 gases to oxygen electron cyclotron resonance (ECR) plasma on the reactive ion etching (RIE) properties of RuO2 film such as etch rate, selectivity, and etched profile. The concentration of the etching species in the plasma was analyzed with an optical emission spectroscopy (OES) and a quadrupole mass spectrometer (QMS). The etch product was also examined with QMS.

The addition of a small amount of CF4, Cl2, or N2 to the O2 plasma increases the concentration of oxygen radicals and accordingly increases the etch rate of the RUO2 films appreciably. The etch rate of the RuO2 film was enhanced more with the addition of a small amount of CF4 and CI2 than with the addition of N2. On the contrary, the etched profile obtained in O2/N2 plasma was superior, without any damaged layer at the sidewall, to O2/CF4 and O2/Cl2 plasma. The selectivity of RuO2 to Si)2 mask was over 20:1 for each of the additive gas proportion at which the etch rate was maximum for each plasma system.

Highly textured PbZrxTi1−xO3 (PZT) thin films with x= 0-0.6 were grown on LaNiO3 coated Si substrates at 600 °C by metal-organic chemical vapor deposition (MOCVD). The preferred crystalline orientation of PZT thin films with various Zr concentration were characterized by X-ray diffraction (XRD). Microstructures were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The dielectric constants, hysteresis and fatigue behavior of these thin films were also measured. The relationship between growth rate and the preferential orientation is discussed. Furthermore, the dependence of the electrical properties on Zr concentration and preferential orientation is demonstrated.

The structural characteristics of SrRuO3 thin films deposited on a (001) SrTiO3 substrate by pulsed laser were studied by transmission electron microscopy (TEM) and high-resolution TEM. TEM studies of cross-sectional specimens revealed the epitaxial growth of the films with the SrRuO3-(110) plane parallel to the SrTiO3-(001) plane. Two types of 90° rotational domain structures were observed in both cross-sectional and plan-viewing specimens. The in-plane orientations of these domains with respect to the substrate are either of SrRuO3-[110] // SrTiO3 - [100] and SrRuO3-[001] // SrTiO3-[010], or of SrRuO3-[110] // SrTiO3-[010] and SrRuO3-[001] // SrTiO3-[100].

In this study, Ir/IrO2 mixture electrodes are fabricated by furnace oxidation of sputter deposited Ir, IrO2 and their hybrid electrodes. The characteristics of furnace oxidation of various electrode stems with Ir family and their limitation are investigated. Annealing at higher than 700°C oxidation results in formation of undesirable extrusions in Ir electrode. When the Ir oxide facet extrusions are formed, Ir near at the extrusion is used up and SiO2 substrate are exposed. In addition, furnace oxidized Ir/Ti electrode is suggested as an alternative electrode, which shows smooth surface, good thermal stability, high oxygen contents and low resistivity.

We characterize, via selected area electron diffraction and high resolution TEM, the multistage crystallization process by which strontium bismuth tantalate(SBT) thin films are transformed from initial amorphous phase to the fully formed layer-structured perovskite. During the annealing process at 800°C, we found that an intermediate fluorite-like stage is formed after 3min as the SBT precursor crystallizing into the final SBT structure. This new information will be very important for formation and crystallization of ferroelectric SBT films.

Thin films of layered-structure solid-solution material, (1−x)SrBi2Ta2O9−xBi3Ti(TayNb1−y)O9, have shown much improved ferroelectric properties compared to SrBi2Ta2O9, a leading candidate material for ferroelectric random access memory applications. The higher Pr, higher Tc, and lower crystallization temperature of the thin films of solid solution material promise to solve many problems with the present materials of interest. The films were fabricated by metalorganic solution deposition technique using room temperature processed alkoxide-carboxylate precursor solution and characterized in terms of structural, dielectric, and ferroelectric properties. It was possible to obtain a pyrochlore free crystalline phase at an annealing temperature of 600 °C. The effects of annealing temperature and excess Bi content on the film microstructure and properties were analyzed. The electrical measurements were conducted on metal-ferroelectric-metal (MFM) capacitors using Pt as the top and bottom electrode. It was possible to obtain good ferroelectric properties on films annealed at 650 °C. For example, thin films with 0.7SrBi2Ta2O9-0.3Bi3TiTaO9 composition, which were annealed at 650 °C, exhibited typical 2Pr and Ec values of 12.4 μC/cm2 and 80 kV/cm, respectively. The films exhibited low leakage current density, good fatigue characteristics under bipolar stressing at least up to 1010 switching cycles, and good memory retention characteristics after about 106 s of memory retention indicating a favorable behavior for memory applications.

SrBi2Ta2O9 (SBT) is a promising material for ferroelectric random access memories (FERAM's) because it has high resistance to fatigue and imprint combined with low coercive field. Metalorganic chemical vapor deposition (MOCVD) offers the ability to produce high quality, conformai SBT films for both high and low density memory applications. An MOCVD process based on liquid delivery and flash vaporization has been developed which allows precise delivery of low vapor pressure precursors to the process. Precursor decomposition has been examined over a wide temperature range and the effects of process pressure have been examined. It is shown that Bi(thdb is superior to Bi(Ph)3 as a source of Bi, offering a wide decomposition window with compatible Sr and Ta precursors so that a simple, well-controlled, and repeatable process is achieved at low temperatures. Films with 90% conformallity have been grown on 0.6 μm structures with a 1:1 aspect ratio. The MOCVD process yields the fluorite phase, which is transformed to the ferroelectric layered perovskite phase upon annealing in oxygen. Dielectric constants (ε) of 200 and remanent polarization (2Pr)up to 16 μC/cm2 have been achieved on 150 mm wafers.

Stable SBT sols for FRAM application were made from Sr-isopropoxide, Bi-acetate, and Ta-ethoxide with 2-ethoxyethanol as a solvent and chelating agent, TEA. The sol were spin-on coated on the Pt /Ti/SiO2/Si substrate. From the IR and DTA/TGA, the 2-ethoxyethanol -triethanolamine sol system is quite stable against aging. 5% excess Bi added sol and 800°C heat treatment of the thin film revealed the most crystallinity. There is a change in the orientation of thin film above 800°C heat treatment from c-axis to(105). The average grain size of thin film is very small, i.e., 40 nm at 800°C, and it has very narrow distributions, and the thickness of the coating were about 100nm, which would promise smaller electrode area and higher yield.

Thin films of SrBi2Nb2O9 (SBN) with thickness of 0.1, 0.2, 0.3 and 0.4 μm were grown by sol-gel technique on platinum/silicon substrates, and annealed at 800°C. Raman spectra of the samples present bands around 170,210, 272, 300,430, 580, 717, and 839 cm−1 which correspond to the SBN formation. The prominent Raman band around 839 cm−1, which is the Alg mode of the orthorhombic symmetry, is assigned to the symmetric stretching of the NbO6 octahedrals. The frequency of this band is found to shift at different places in the same sample, as well as from sample to sample. The frequency and width variations of the Raman bands are discussed in term of ions in non-equilibrium positions, which seem to be related with the crystallization degree in the SBN samples. Also, the Raman study indicates the presence of foreign sharp peaks, which are associated with the coexistence of phases other than SBN. The thickness dependence of the Raman spectra and the X-ray diffraction are also discussed. Finally, the experimental results of the SBN/Pt/Si films grown at 800°C are compared with those obtained at 650°C.

We have made a comparative invetigation of the surface microstructures of epitaxially grown ferroelectric SrBi2Ta2O9, BaTiO3 films, and metallic SrRuO3 films, using scanning probe microscopy. Though their lattices (or pseudotetrogonal lattices) match closely with SrTiO3 (001) substrates, SPM results show very different surface microstructures. The surfaces of SrRuO3 films display atomically flat terraces of 90° oriented step edges. The size of steps is about 6 Å. The surface of BaTiO3 films deposited at various temperatures displays uniform rectangular islands. Different stages of SrBi2Ta2O9 epitaxial growth have been studied on thickness gradient films, which show clearly 2D nucleation and layer-by-layer growth, following a transition from 2D to 3D island growth. It finally develops into a surface exhibiting round hills consisting of curved terraces with size of steps ranging from 6 Å to 12.5 Å.

The electronic structure of SrBi2Ta2O9 and related oxides such as SrBi2Nb2O9, Bi2WO6 and Bi3Ti4O12 have been calculated by the tight-binding method. In each case, the band gap is about 4.1 eV and the band edge states occur on the Bi-O layers and consist of mixed O p/Bi s states at the top of the valence band and Bi p states at the bottom of the conduction band. The main difference between the compounds is that Nb 5d and Ti 4d states in the Nb and Ti compounds lie lower than the Ta 6d states in the conduction band. The surface pinning levels are found to pin Schottky barriers 0.8 eV below the conduction band edge.

Ferroelectric Bi4Ti3O12 thin films were prepared by the sol-gel method to examine the effect of precursors on the variation of ferroelectric properties. Two kinds of Bi4Ti3O12 sol-gel precursor solutions were synthesized by dissolving bismuth acetate and bismuth nitrate in glacial acetic acid and then adding titanium acetate. The films were deposited on Pt coated Si substrates by the spin-coating method and crystallized by double heat-treatment. The Ps, the Pr, and the Ec values of the film derived from the Bi-acetate were 34.8 μC/cm2, 16.2 μC/cm2, and 128 kV/cm, respectively. The Ps, the Pr, and the Ec of the films from the Bi-nitrate were 14.2 μC/cm2, 5.7 μC/cm2, and 105 kV/cm, respectively. The Bi4T3O12 films prepared from the Bi-acetate revealed better ferroelectricity and resistivity compared to those obtained from the Bi-nitrate.

Ferroelectric thin films of Bi-containing layered perovskites such as Bi4Ti3O12, PbBi2Nb2O9 and SrBi2Nb2O9 have been processed by metal-organic decomposition (MOD) method. Films with random or c-orientation have been obtained via different heat treatment. Nucleation control has been identified as the mechanism for the texture evolution in these films. A strong polarization anisotropy has been observed which corresponds to the layered polarization in the crystal structure. The fatigue test results show that Ti seems to be a common species that exists in fatigue-prone ferroelectrics.