Piezoelectric and electrostrictive responses in poled and unpoled ferroelectric and relaxor ferroelectric compositions are of importance in transducers for converting electrical to mechanical impulses and vice-versa. Sensor applications make use of the very high piezoelectric constant dijk of the converse effect, which also permit efficient conversion of electrical to mechanical response. One of the most important families of materials for piezoelectric applications is Pb(Zr,Ti)O3(PZT). The most widely studied composition of PZT lies at the boundary between the tetragonal and rhombohedral phases, known as the morphotropic phase boundary (MPB) and exhibits greatly enhanced dielectric and piezoelectric properties in bulk and thin film. In modern electronic applications, pyroelectric detectors, piezoelectric microsensors, and micromechanical pumps require the integration of PZT films into a variety of device structures. To get sufficiently large piezoelectric strains for optimization of the performance and reliability of the device, thick films in the thickness range of 5–50 μm are desired. On the other hand burying the device components within the substrate is of utmost importance for miniaturization. In comparison to traditional surface mounted components embedded ones will free surface space for a higher functionality of the device, reduce solder points and increase device reliability. Additionally, to reduce the device costs the use of flexible copper foil as substrates is of particular interest. Its high conductivity and compatibility with printed circuit boards makes copper an attractive candidate substrate for embedded application. However, depositing PZT thick films on copper is not trivial, due to the conflict between the high temperature required to sinter PZT (∼1150°C) and low melting temperature of Cu (∼1050°C), in addition to the easy oxidation of Cu. As a consequence the preparation of PZT thick films on Cu involves a complex route to decrease the ceramic sintering temperature and to control the oxygen partial pressure. So far, no successful deposition of PZT thick films on copper foils was reported.

The consequence of tungsten metal purity on the electrical properties of an annealed MOS gate stack with a lanthanum silicate gate dielectric has been investigated. Optimization of the electrical and physical properties of a device with any given dielectric requires the proper choice of metal gate electrode and capping layer. This study is intended to show the importance of tungsten processing optimization and subsequent effects on the equivalent oxide thickness, fixed charge, and density of interface states of La-Si-O gate dielectric MIS devices. In the experiment, La-Si-O films of physical thickness of 1.6 nm were deposited on a Si substrate, subsequently depositing TaN as the gate electrode and W as a capping layer. A post metallization anneal in flowing nitrogen at 1000°C for short times resulted in widely different measured properties of the MIS devices, dependent on the quality of the tungsten deposited. XRD and SIMS profiles of the gate stacks showed a clear relationship between concentration of oxygen and processing of the tungsten. A 1000°C, 10 sec anneal resulted in an EOT change from 1.1 nm to 2.2 nm on gate stacks with low and high oxygen concentration in the tungsten, respectively. Defect densities decreased with increased anneal temperature and time, and annealing with low oxygen-concentration tungsten resulted in higher effective fixed charge. SIMS data suggests that oxygen in the tungsten diffuses to the Si/La-Si-O interface through the TaN electrode, resulting in the observed differences in the defect densities and EOT.

PZT (52/48) and PLZT (7/65/35) thin films were prepared by chemical solution deposition (CSD) on Pt/SiO2/Si and Cu foil substrate, respectively. For PZT thin films on Pt/SiO2/Si substrates, pO2 control during thermal treatment affected both perovskite phase formation and orientation, but did not show significant impact on the ferroelectric and dielectric properties. When PLZT thin films (7/65/35) were prepared on Cu foil to tailor ferroelectric/dielectric properties, it was observed that ferroelectric and dielectric properties were significantly affected by the strains, possibly from the coefficient of thermal expansion (CTE) mismatch between PLZT and Cu foil during cooling after high temperature crystallization. It was also experimentally observed that, depending on the direction of applied strain, the PLZT films could be cycled between ferroelectric and paraelectric phases. It was suggested that PZT based thin films on base metal substrate requires very careful processing for optimized electrical performance.

Ca-doped lead zirconate titanate (52/48) thin film capacitors were prepared on electroless nickel-coated copper foils for embedded capacitor applications. The impact of Ca doping and process parameter variations was studied. Ca addition significantly reduced the temperature coefficient of capacitance. Specifically, the temperature variation was reduced to less than 10% between 300 and 580 K through calcium addition. Optimized capacitance densities and loss tangents were 400 nF/cm2 and 0.02, respectively. Crystallization temperatures of 600 °C yielded these optimized electrical properties, while higher temperatures resulted in interfacial reactions. The influence of oxygen partial pressure during crystallization was also studied. Dielectric properties were sensitive to pO2, with optimal properties occurring in a narrow pO2 window centered about 10−3 Torr. The trends with oxygen pressure were mirrored by changes in phase assemblage. Electrical transport across the dielectric layers was not strongly dependent upon doping level. This insensitivity was attributed to a thin interfacial layer present in all samples. Interface analysis using equivalent circuit analogues showed the nature of the interface to be highly resistive (insulating), rather than semiconducting or conducting.

AC-coupled interconnects (ACCI) is a very exciting technology for achieving high-density chip-to-package interconnects while simultaneously providing a simple, mechanically robust interface. The technology combines the stress-relieving ‘underfill’ layer with the dielectric medium for capacitive coupling. For good AC coupling, it is desirable for the underfill material to have a permittivity around 20 at operating frequencies. However, there is a lack of microwave frequency data for high permittivity ceramic-polymer composite systems in the literature. This paper describes the development and microwave frequency characterization of high K nanocomposite underfill. For composite thick film preparation, 200 nm BaTiO3 nano-sized powder and photosensitive epoxy were used. The thermal behavior of composites was evaluated by DSC (differential scanning calorimetry). Dielectric properties were evaluated as a function of ceramic loading and curing temperature. The microwave dielectric properties were measured from 45 MHz up to 26.5 GHz to extract the capacitance and quality factor of the capacitor over the frequencies of interest using floating plate capacitors and T-resonator CPW structures. The permittivity was found to be ∼ 18 up to 14 GHz and the total Q factor of the capacitors was found to be 2 at 26.5 GHz for BaTiO3 (30 vol%)-epoxy composite. Dielectric loss was found to be 0.3 at 3 GHz, which would satisfactorily allow signaling well into the muti-gigabits range. The high K nanocomposite shows higher permittivity compared to materials currently used (air, K=1 or SiO2, K∼3.9) in capacitively coupled interconnects for chip-to-package communications.

Barium titanate thin films have been prepared by chemical solution deposition on 18 μm thick, industry standard copper foils in the absence of chemical barrier layers. The final embodiment exhibits randomly oriented BaTiO3 grains with diameters between 0.1 and 0.2 μm, and an equiaxed morphology. The average film thickness is 0.6 μm and high resolution cross sectional microscopy shows no indication of interfacial phases. The BaTiO3 films are sintered in a high temperature reductive atmosphere such that copper oxidation is avoided. Subsequent lower-temperature, higher oxygen pressure anneals are used to minimize oxygen point defects. Permittivities greater than 3000 are observed, with loss tangents under 2.5%. The BaTiO3 phase exhibits pronounced ferroelectric switching and coercive field values near 20 kV/cm. Temperature dependent measurements indicate a ferroelectric transition near 100 °C with very diffuse character. Combining the approaches of the multilayer capacitor industry with traditional solution processed thin films has allowed pure barium titanate to be integrated with copper. The high sintering temperature – as compared to typical film processing – provides for large grained films and properties consistent with well-prepared ceramics. Integrating BaTiO3 films on copper foil represents an important step towards high capacitance density embedded passive components.

HfO2–SiO2 and La2O3–SiO2 amorphous alloys were prepared, and their crystallization behavior was studied. The results suggest that higher permittivities can be achieved in the La-containing system without devitrification. The crystallization mechanisms between systems are distinctly different, yet observations are consistent with bulk material. Hf-containing materials tend toward phase separation, while La-containing materials tend toward silicate formation. For Hf-containing films, negligible thickness or time dependence was observed. In La-containing films, rapid thermal anneals could improve crystallization resistance, and thickness effects related to interface reactions were observed. These behaviors are discussed in the context of phase diagrams and metastable immiscibility.

The preparation of high-permittivity perovskite materials requires high-temperature (550–750 °C) oxidizing environments, providing stringent limitations on the choice of electrode materials. To minimize interdiffusion and oxidation reactions, an electrically conductive diffusion barrier such as Ti1−xAlxN is needed below the electrode material (Pt, IrO2, RuO2…). Ti1−xAlxN films were deposited by multitarget reactive sputtering in a mixture of Ar and N2. The stability of these films has been investigated under typical conditions for crystallization of perovskite dielectrics. Sample composition was characterized using Rutherford backscattering spectroscopy and nuclear reaction analysis. In particular, the concentration depth profiles of both 18O and 27Al were measured before and after 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). The different 18O excitation curves show that the oxidation resistance increases with Al incorporation. The Al excitation curves indicate a uniform Al content for as-deposited TixAl1−xN and reveal Al diffusion to the surface during the oxidation process which indicates the formation of an Al-rich oxide layer at the TixAl1−xN surface, leaving a layer depleted in Al below it.

The degradation behavior of polarization and leakage current characteristics of sol-gel-derived (Pb,La)(Zr,Ti)O3 (PLZT) thin films, with Pt, Ir, and IrO2 top electrodes, by annealing under a 4% H2/96% N2 atmosphere were investigated. The leakage current behaviors of Pt/PLZT/Pt and IrO2/PLZT/Pt capacitors annealed at 300 °C for 20 min in 4% H2 were well consistent with the space-charge-influenced injection model proposed. However, IrO2/PLZT/Pt capacitors recovered at 700 °C for 10 min in Ar ambient after hydrogen anneal were not consistent with the proposed model because a conducting phase of IrPb was formed between the top electrode and PLZT during the recovery anneal at 700 °C in Ar ambient and modified the Schottky barrier height. The true leakage current behavior of IrO2/PLZT/Pt capacitors recovered after hydrogen forming are similar to those of Ir/PLZT/Pt capacitors without the hydrogen-forming gas anneal. The P–E loops of Pt/PLZT/Pt and Ir/PLZT/Pt capacitors showed good recovery through recovery anneal after H2 treatment. However, IrO2/PLZT/Pt capacitors depended on the recovery anneal atmosphere (Ar or O2).

Piezoelectric properties of wurtzite AlN and GaN/AlN are investigated using scanning force microscopy (SFM). The magnitude of the effective longitudinal piezoelectric constant d33 of AlN and GaN/AlN thin films are measured and reported, and the d33 coefficients of these films are verified using an interferometric technique. Simultaneous imaging of the topography, and of the phase and magnitude of the piezoelectric strain is performed. Using a GaN film with patterned polarities, we demonstrate that polarity can be inferred from the phase image of the piezoelectric strain. We report d33=3±1 pm/V for AlN/SiC and 2 1 pm/V for GaN/AlN/SiC. Films grown by organo-metallic vapor phase epitaxy (OMVPE) on SiC, sputtered AlN films and films grown by molecular beam epitaxy (MBE) are characterized and compared.

The piezoelectric, dielectric, and ferroelectric properties of highly (111)-textured polycrystalline lead zirconate titanate (PZT) films as a function of Zr/Ti composition have been investigated. The peak in piezoelectric coefficient at the morphotropic phase boundary (MPB) observed in bulk PZT ceramics has not been found in thin film PZTs. Measurement of the piezoelectric response as a function of AC amplitude suggests that non-180° domain wall motion in these films is negligible, indicating that the extrinsic contribution to the room temperature dielectric constant is dominated by only 180° domain wall motion. The semi-empirical phenomenological equation relating the piezoelectric coefficient to measured polarization and permittivity values is demonstrated to give an excellent description of the piezoelectric behavior in these films, assuming bulk electrostrictive coefficients. The small deviation between calculated and measured piezoelectric coefficients as well as the dependence of piezoelectric and polarization behavior on the external dc field, i.e., hysteresis loop, are suggested to be primarily due to backswitching of 180° domains.

Due to its resistance to oxidation, TaSiN is a promising candidate as an electrically conductive barrier layer for integration of high permittivity oxides in advanced memory devices. In this study we report on the properties and the resistance to oxidation of TaSiN thin films deposited by reactive magnetron sputtering and processed by rapid thermal annealing (RTA) in 18O2 at 650°C. In order to determine the composition, RBS (Rutherford Backscattering Spectroscopy) and NRA (Nuclear Reaction Analysis) techniques have been used. 18O depth profile concentrations were measured after RTA using the narrow (fwhm=100eV) resonance at 151 keV in the nuclear reaction 18O(p,α)15N.

Ferroelectric SrBi2Ta2O9 (SBT) thin films on Pt/ZrO2/SiO2/Si were successfully prepared by using an alkanolamine-modified chemical solution deposition method. It was observed that alkanolamine provided stability to the SBT solution by retarding the hydrolysis and condensation rates. The crystallinity and the microstructure of the SBT thin films improved with increasing annealing temperature and were strongly correlated with the ferroelectric properties of the SBT thin films. The films annealed at 800 °C exhibited low leakage current density, low voltage saturation, high remanent polarization, and good fatigue characteristics at least up to 1010 switching cycles, indicating favorable behavior for memory applications.

Mixed composition layered lead zirconate titanate (PZT) films sZr/Ti ratio = 30/70 + 65/35d with stoichiometric lead containing PZT thin layer at the film/electrode interface were successfully fabricated by a modified chemical solution deposition method. These modified PZT thin films are highly (111) textured, and have square-shaped P-E hysteresis loops with large remanent polarization and low coercive field, as well as low saturation voltage. In addition, these films show good fatigue and imprint behavior with Pt electrodes; the retained polarization of the modified film was above 50% after fatigue testing to 109 cycles, and the thermally induced voltage shifts (ΔV) were 0.51 V after heating at 150 °C for 4410 s, two times lower than for films without a stoichiometric thin layer.

We have investigated the effect of oxygen vacancies on imprint and fatigue behavior of the PLZT thin films. It is found that the compensation of oxygen vacancies with various dopant concentrations and electrode structures is an important process parameter in determining the tendency to imprint and fatigue. In the case of PLZT thin films, the voltage shifts related to imprint are attributed to the trapping of electrons at ionic defect sites such as oxygen vacancies near the film/electrode interface, the magnitude of polarization, and concentration of defect-dipole complexes involving oxygen vacancies such as V′Pb–V••o. The strong dependence of fatigue rate on electrode material for PLZT thin films is due to the effect of the ferroelectric/electrode interaction on the pinning and/or unpinning rate involving the accumulation of oxygen vacancies near the film/electrode interface during fatigue cycling. By using RuO2 as the top and/or bottom electrode instead of Pt, improved fatigue properties are obtained compared to Pt/PLZT/Pt capacitors. This is because a reduced accumulation of oxygen vacancies near the interface by the oxide electrode such as RuO2 may reduce the electronic charge trapping and, consequently, lead to less domain wall pinning.

We have investigated the effect of RuO2 (10, 30, 50 nm)/Pt layered hybrid bottom electrode structure and film composition on the leakage and fatigue properties of chemical solution derived Pb(ZrxTi1−x)O3 (PZT) thin films. It was observed that the use of high Ti content (Zr: Ti = 30: 70) films with control of excess PbO at the thin RuO2 (10 nm)/Pt bottom electrode surface reduced leakage current and showed good fatigue properties with high remanent polarization compared to the use of high Zr films (Zr: Ti = 50: 50) or thicker RuO2 (30, 50 nm)/Pt bottom electrodes. Typical P-E hysteresis behavior of PZT films was observed even at an applied voltage of 3 V, demonstrating greatly improved remanence and coercivity. Fatigue and breakdown characteristics of these modified PZT thin films (Zr: Ti = 30: 70) on RuO2 (10 nm)/Pt, measured at 5 V, showed stable behavior, and less than 15% fatigue degradation was observed up to 1010 cycles.

There has been significant interest recently in use of BaSrTiO3 (BST) thin films for integrated capacitors; these devices have benefits for high frequency operations, particularly when high levels of charge or energy storage are required. We discuss the electrical properties of BST thin films grown by metalorganic chemical vapor deposition (MOCVD) which make them suitable for these applications, as well as the impact of processing conditions such as growth temperature on specific film properties. We have also examined addition of Zr in amounts ranging up to 20% to the BST films. X-Ray diffraction indicates that the Zr is incorporated into the BST lattice. Voltage withstanding capability, leakage and dielectric constant of the thin films have been measured as functions of deposition temperature and Zr content. Addition of Zr to BST films increases breakdown voltages by as much as a factor of two, to approximately 2 MV/cm, raising their energy storage density values to levels approaching 30 J/cc. Charge storage densities of above 60 fF/µm2were also obtained.

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.

Ni,Zn-ferrite (NZF) thin films are of interest for high frequency applications because of their high saturation magnetization compared to garnet films and their low eddy current losses compared to metal alloy films. Therefore there is an increasing need for methods to deposit single crystal ferrite thin films for incorporation into next generation microwave devices.

Epitaxial thin films of NZF have been deposited by liquid delivery metal-organic chemical vapor deposition onto (100) oriented MgO substrates. The morphology, orientation and magnetic properties of the as-deposited films were investigated as a function of deposition temperature and pressure. X-ray diffraction (XRD) reveals highly oriented films with a film strain of 1.01% compared to bulk lattice parameters. Films with well saturated magnetic hysteresis were obtained under a number of conditions with values of saturation magnetization up to 270 emu/cc (3400 gauss) with relatively low coercive fields ~100 Oe. The influence of metal cation ratio on magnetic properties is discussed.