PZT thin films of different thicknesses and Zr/Ti ratios of 60/40, 52/48 and 45/55 were coated onto platinized silicon substrates by using 2 methoxyethanol (2-MOE) based sol-gel spinon technique and crystallized with a rapid thermal annealing (RTA) process. XRD analysis revealed that thin PZT films exhibit random texture, while the thicker ones exhibit (100) texture, which was independent of composition. Dielectric constants and dissipation factors of PZT thin films were measured at elevated temperatures and as a function of frequency. For films with a thickness of ∼ 4 μm, the Curie points are at 350, 375 and 422°C for Zr/Ti ratios of 60/40, 52/48 and 45/55, respectively. All these films exhibit a high remnant polarization. A remnant polarization of 35 μC/cm2 had been achieved for the 60/40 films. No enhancement of the dielectric constant was observed in films with a composition close to MPB. The higher dielectric constant observed in films with the highest Zr content was explained by the concept of domain engineering.

Mapping of polarization distributions in Pb(Zr,Ti)O3 ferroelectric capacitors with sizes down to 0.5 × 0.5 μm has been studied using scanning probe microscope (SPM) with detection of piezoelectric response through the top electrode. A well reproducible anomaly in polarization distribution namely elevated polarization at the edges and inverse polarization in the center has been observed for the FeCaps of several μm size. This polarization pattern is found to be insensitive to the poling voltage polarity and voltage stress prehistory but strongly dependent on the FeCAP size. Specifically, the polarization anomaly tends to disappear as the FeCAP size scales down to the submicron range. Tentative interpretation of this phenomenon in terms of strain-induced phase transitions in combination with depolarization effects is discussed.

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

Noble metals like platinum or irdium are used as electrode materials in DRAM or FRAM devices. Their etch process is a challenge as conventional, sputter driven etch processes either result in redeposition problems (fences) or in a severe sloping (loss of dimension control) and are not acceptable for high density integration architectures. The high temperature etch regime offers a solution by increasing the chemical etch component and thus the volatility of the etch products.

As previously reported, the platinum etch rate increases exponentially for a chlorine etch process with increasing wafer temperature. In this study we investigate the particular role of carbon monoxide in a Cl2/CO etch process. We find that carbon monoxide additions to a chlorine process boost the chemical component of the platinum etch rate very significantly, exceeding the effects in the chlorine only process regime by far. Additionally we compare these results with a Cl2/O2 and a Cl2/CO2 process chemistry, which are not found to be particularly beneficial.

To better understand the etch process we use an energy dispersive quadrupole mass spectrometer for in situ monitoring, attached to the chamber at two different locations. We are able to position the probe orifice at the place of the wafer electrode, to record ion energy and ion mass spectra of species impinging on the wafer plane. A second off axis position allows for etch product monitoring.

The local potential at domains on ferroelectric surfaces results from the interplay between atomic polarization and screening charge. The presence of mobile charge affects surface domain configuration, switching behavior, and surface chemical reactions. By measuring the temperature and time dependence of surface potential and piezo response with scanning probe microscopies, thermodynamic parameters associated with charge screening are determined. This is illustrated for the case of BaTiO3 (100) in air, for which the charge compensation mechanism is surface adsorption and enthalpy and entropy of adsorption are determined. The local electrostatic fields in the vicinity of the domains have a dominant effect on chemical reactivity. Photoreduction of a large variety of metals can be localized to domains with the appropriate surface charge. It has been demonstrated that proximal probe tips can be used to switch polarization direction locally. Combining the ability to ‘write’ domains of local polarization with domain specific reactivity of metals, vapors of small molecules, and organic compounds leads to a new approach to fabricating complex nanostructures.

RhO2 belongs to the family of conducting oxides with a rutile structure, which have attracted attention as capacitor electrode materials for memory devices. In this study, effects of thermal treatment under various oxygen pressures on structural and electrical properties of RhO2 thin films prepared by reactive sputtering were investigated. The RhO2 films were found to be stable up to 700°C under oxygen pressure of 1 atm and a metallic conduction property with a resistivity of about 80 μΩcm was obtained. However, the RhO2 films decomposed to semiconducting Rh2O3 at 750°C. The decomposition temperature decreased to 500°C under oxygen pressures of 0.5-5 mTorr.

Polarization versus applied field (P-E) hysteresis loop measurements on Pb(Zr,Ti)O3 (PZT) thin films were performed using a controlled-atmosphere probe station. Measurements were made using two different capacitor configurations, each producing differing results. The capacitor configurations included using either the typical arrangement of two top electrodes (planar) or an arrangement using contacts to the top and the bottom electrodes (sandwich). The films included PZT films deposited using pulsed laser deposition (PLD) and commercially-available rfsputtered PZT thin films. Qualitatively similar results were obtained for both types of films. For both PLD and Ramtron PZT films, translation of ferroelectric hysteresis loops along the polarization axis was observed for sandwich capacitors. The magnitude of this voltage was strongly dependent on the partial pressure of oxygen at room temperature. Translations were not observed for the same films using the planar capacitor configuration. However, for both sandwich and planar configurations, the thin film capacitance was sensitive to changes in pO2.

Pb(Zr,Ti)O3 (PZT) is one of the most promising materials for ferroelectric random access memory (FeRAM) application. Among the various preparation methods, metalorganic chemical vapor deposition (MOCVD) has been recognized as a most important one to realize high density FeRAM because of its potential of high-step-coverage and large-area-uniformity of the film quality.

In the present study, pulsed-MOCVD was developed in which a mixture of the source gases was pulsed introduced into reaction chamber with interval. By using this deposition technique, simultaneous improvements of the crystallinity, surface smoothness, and electrical property of the film have been reached by comparing to the conventional continuous gas-supplied MOCVD. Moreover, this film had larger remanent polarization (Pr) and lower leakage current density. This is owing to reevaporation of excess Pb element from the film and increase of migration on the surface of substrate during the interval time.

This process is also very effective to decrease the deposition temperature of the film having high quality. In fact, the Pr and the leakage current density of polycrystalline Pb(Zr0.35Ti0.65)O3 film deposited at 415 °C were 41.4 μC/cm2 and on the order of 10−7 A/cm2 at 200 kV/cm. This Pr value was almost the same as that of the epitaxially grown film deposited at 415 °C with the same composition corrected for the orientation difference. This suggests that the polycrystalline PZT film prepared by pulsed-MOCVD had the epitaxial-grade ferroelectric properties even through the deposition temperature was as low as 415 °C. Moreover, large “process window” comparable to the process window at 580 °C, above 150 °C higher temperature and was widely used condition, was achieved even at 395°C by the optimization of the deposition condition.

Monte Carlo simulations of capacitors with polycrystalline (Bax, Sr1−x)TiO3 (BST) dielectrics were performed. The variation in capacitors due to the polycrystalline microstructure of the dielectric was investigated, as well as the effects of varying the distribution of crystal sizes. When a lognormal probability density function (pdf) was used to approximate the crystal area pdf and the average number of crystals per capacitor was near 100, it was found that the minimum capacitance value was nearly independent of the standard deviation of crystal area distribution. Both the mean and maximum capacitance values were found to increase as the width of the standard deviation increased.

SrTiO3 and PbTiO3 perovskites are combined to form the xPbTiO3-(1−x)SrTiO3 (PST) solid solution. The effect of the PbTiO3 content on the microstructural and dielectric properties is studied for different compositions (x=0.1,0.3,0.5,0.7, and 0.9). Microstructural features of the PST system are studied by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. Electrical properties are studied by the thermoelectric analysis technique at both fixed frequency and varying frequency to study the behavior of the dielectric constant and dielectric loss.Films of 0.5PbTiO3-0.5SrTiO3 (PST50) have been obtained by RF ion sputtering on different substrates. We investigate the relation between the crystalline structure and the dielectric properties of PST50 films deposited on different metallic films. Scanning Electron Microscopy (SEM) and X-Ray Diffraction were used for the structural analysis of the PST50/TiN/Si and PST50/RuO2/TiN /Si systems. The dielectric properties of the PST50 films were measured for TiN/PST50/TiN/Si, and RuO2/PST50/RuO2/TiN/Si capacitors and the results were correlated to the structure and composition. The charge storage capabilities of the PST50 films are evaluated for possible application in integrated circuit technology.

Thin film electrodes of the perovskite oxide (Ba,Sr)RuO3 (BSR) were deposited on 4 inch ptype Si wafers by metal organic chemical vapor deposition (MOCVD) for the practical (Ba,Sr)TiO3 (BST) capacitor application using a new single cocktail source. The source materials used for the MOCVD BSR process were Ba(METHD)2, Sr(METHD)2 and Ru(METHD)3 and these were dissolved in n-butyl acetate. The source-feeding rate was precisely controlled by liquid mass flow controllers (LMFC). As-deposited BSR films possessed a (110)-oriented structure, with good uniformity and adherence on bare Si wafer. The phase formation was strongly affected by the oxygen flow rate and the input source rate. As the oxygen flow rate increased, the Ru/(Ba+Sr) composition ratio in the film decreased, while the Ba/(Ba+Sr) ratio was almost independent of the oxygen flow rate. The dielectric constants of BST capacitors fabricated using these electrodes was greater than 500.

We have prepared single crystalline epitaxial PbZr0.52Ti0.48O3 (PZT) and BaTiO3 (BTO) thin films on single crystalline epitaxial SrRuO3 (SRO) thin films grown on SrTiO3 (100) (STO) substrates. PZT and SRO thin films were grown using high-pressure on-axis sputtering and BTO using pulsed laser deposition (PLD). The film thickness ranged between 12 to 165 nm. Their excellent structural properties, surface smoothness and interface sharpness were demonstrated by X-Ray Diffraction measurements (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Atomic Force Microscopy (AFM). Rutherford Backscattering Spectrometry and Channeling measurements (RBS/C) were used to analyze stoichiometry and crystalline quality. Ferroelectric hysteresis loops were obtained for all films of a thickness down to 12 nm showing a decrease in the remanent polarization Pr and an increase in the coercive field Ec towards thinner film thicknesses. Furthermore we have prepared tunneling junctions with a PZT or BTO barrier thickness of 3-6 nm. Reproducible bi-stable I-V-curves and bias dependence of the conductance were obtained suggesting an influence of the ferroelectric properties of the barrier material on the tunnel current.

Ferroelectric Bi4Ti3O12 (BIT) thin films were modified by the substitution of Sr2+ ions for Bi3+ ions and of Nb5+ for Ti4+ (codoping) by spin-coating and decomposition of chemical solutions of metal-alkoxide materials (the nominal compositions of Bi4−xSrxTi3−xNbxO12 where x=0.0, 0.5, 1.0, 1.5). Single-phase thin films were crystallized above 550°C with BIT-type structure. The ferroelectric properties were found, though, with the values of Pr=10 μC/cm2 Ec=100 kV/cm, εr=300, and tanδ<5 % for Bi3.5Sr0.5Ti2.5Nb0.5O12 (x=0.5) annealed at 650 °C. Perhaps due to the lowering of the Curie temperature with increasing x, the maximum value of δr increased.

Temperature dependent dielectric behavior of sol-gel derived ferroelectric Pb1−xLaxTiO3 (PLT) (x = 0.05 to 0.30) thin films on Pt/Si substrates has been studied. The characteristics of the diffuse phase transition and possible relaxor behavior of PbTiO3 thin films doped with different amounts of La are investigated. Room temperature X-ray and micro Raman results indicate that the crystal structure of the PLT films was strongly influenced by the La content. The softening of the E(1TO) mode with increasing La content indicates that the incorporation of La in the PT lattice results in a structural disorder in the material. The dielectric permittivity and loss tangent of the PLT thin films were measured in the temperature range of 80 –700 K at frequencies between 1 kHz and 1 MHz. Transition temperatures (Tm) for PLT (x = 0.05, 0.20, and 0.30) are 640, 460, and 254 K respectively, and are higher in comparison to reported values of bulk ceramics. The permittivity maximum broadened, and showed relaxor- type frequency dependent permittivity characteristics for PLT (x = 0.30) films. The broadening parameter was significantly influenced by La doping and our results indicate that PLT thin films undergo a normal-to-relaxor ferroelectric transformation for La concentrations of 25 at% in PLT films.

Micromachined silicon cantilever beams actuated by the converse piezoelectric effect are of great interest for actuator applications, e.g. micro relays or micro mirrors. For the miniaturization and cost saving aspects the combination of silicon bulk micromachining and chemical solution deposition (CSD) technique for the ceramic thin films is very promising.

This paper presents the results of such a fabrication process for a PbZr0.45Ti0.55O3 (PZT) thin film micro actuator for a switch application. The actuator was designed with lengths of 190-990 μm, widths of 60-120 μm, and a complete thickness of 1.5 μm. Wherein the piezoelectric PZT function layer has a thickness of 350 nm. For a distance of 10 μm between the switch contacts and an applied voltage of 10 V a finite element analysis simulation (FEA) was carried out to obtain the principal stress contribution, the optimum cantilever length, the sensitivity, the resonance frequency and the switch contact force. The bending beams were characterized by laser interferometry, resonance frequency, and force measurements. These characterization results are compared to the FEM analyses and to an analytical approach.

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.

A study was done on pulsed laser deposited relaxor ferroelectric thin films of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) deposited on platinized silicon substrates with template layers to observe the influence of the template layers on physical and electrical properties. Initial results, showed that perovskite phase (80% by volume) was obtained through proper selection of the processing conditions on Pt/Ti/SiO2/Si substrates. The films were grown at 300°C and then annealed in a rapid thermal annealing furnace in the temperature range of 750-850°C to induce crystallization. Comparison of the films annealed at different temperatures revealed a change in crystallinity, perovskite phase formation and grain size. These results were further used to improve the quality of the perovskite PMN-PT phase by inserting thin layers of TiO2 on the Pt substrate. These resulted in an increase in perovskite phase in the films even at lower annealing temperatures. Dielectric studies on the PMN-PT films show very high values of dielectric constant (1300) at room temperature, which further improved with the insertion of the template seed layer. The relaxor properties of the PMN-PT were correlated with Vogel-Fulcher theory to determine the actual nature of the relaxation process.

Strontium bismuth tantalate (SBT) having composition of Sr0.7Bi2.4Ta2O9 has been prepared through sol-gel method using their corresponding metal alkoxides as precursors. Seeded SBT powder was prepared by the addition of 5 wt.% of nanometer sized SBT particles to the sol followed by pyrolysis. By applying non-isothermal kinetic analysis to the DTA results, activation energy values for the unseeded and seeded samples were determined. Enhanced crystallization kinetics was observed for the seeded one and the activation energy for the aurivillius phase formation was found to be 318 kJ/mol, while 375 kJ/mol for the unseeded. The Avrami exponent values for the seeded and unseeded were found to be 2.80 and 0.96 respectively.

The vibrational properties of barium strontium titanate thin films were studied by Raman spectroscopy in the temperature range from 5 to 300 K. The films were grown by pulsed laser deposition on SrTiO3 and LaAlO3 substrates with SrRuO3 buffer layers. Soft phonons are observed in Raman spectra of BaxSr1−xTiO3 films with Ba contents x = 0.05, 0.1, 0.2 and 0.5. The temperature dependence of the soft phonon frequencies and the splitting of the triply degenerated soft mode into two components of A and E symmetries indicate the ferroelectric phase transition. The E soft mode line is overdamped over a broad range of temperatures near the ferroelectric phase transition, while it is clearly seen in the spectra at temperatures away from the phase transition. The relative Raman intensity of the A soft mode and hard modes decreases gradually over a broad range of temperatures. This indicates a broad ferroelectric phase transition in the thin films. Comparison of Raman spectra for films grown on SrTiO3 and LaAlO3 substrates shows the influence of strain on the temperature of the ferroelectric phase transition.

Pb3Ge5O11 (PGO) metal-ferroelectric-metal-oxide-semiconductor (MFMOS) and metalferroelectric-oxide-semiconductor (MFOS) one-transistor ferroelectric memory devices have been fabricated. The memory windows of the memory transistors can be characterized in terms of MFMOS or MFOS capacitor and the threshold voltages of the transistor. The retention properties of one-transistor memory devices can be measured from the changes of the capacitance of MFMOS or MFOS capacitors. Alternatively the retention properties can be evaluated from the threshold voltages or drain currents of the transistor with retention time. There are inconsistencies between the capacitor data and the transistor data. In this paper, we present the memory windows and retention properties of MFOS and MFMOS one-transistor memory devices measured with various methods. The different results obtained from various methods and device structures will be discussed.