A novel technique to measure the Curie temperature of ferroelectric thin films has been developed. The method is based on identifying changes in slope of film stress vs temperature plot. At the Curie temperature, ferroelectric films undergo a phase transition from ferroelectric phase to paraelectric phase. Due to this phase transformation, physical properties of films such as elastic constants and coefficients of thermal expansion also change at the Curie temperature. Consequently, at this temperature the temperature coefficient of film stress changes since it is related to elastic constants and thermal expansion coefficient. Thus, by measuring the film stress as a function of temperature, the Curie temperature can be determined. The Curie temperatures measured by this method are in good agreement with the literature values. Small discrepancies that were observed can be attributed to the intrinsic stresses present in the films.

The primary objective of this study is to demonstrate an in–situ stress measurement technique for the study of formation kinetics of multicomponent thin films such as PbTiO3. Film stress–temperature and film stress–time plots have been successfully used to monitor the phase formation of PbTiO3 films in a in–situ way. It is believed that the mechanism of this reaction was dominated by grain boundary diffusion of the participating cations. The activation energy of the PbTiO3 phase formation from PbO/TiO2 double layers was estimated to be 108 kcal/mole.

Amorphous thin films of ferroelectric oxides including lead zirconate titanate (PZT), barium titanate (BaTiO3) and lithium niobate (LiNbO3) on several kinds of substrates were prepared by a sol-gel technique. The heat-treatment temperatures for preparation of amorphous thin films were much lower than those for the corresponding crystalline ferroelectric thin films. Electrical properties of these amorphous thin films were measured and compared with those of corresponding crystalline films. These amorphous thin films exhibited ferroelectric-like behavior. A model of the microstructure of these films is proposed.

The need for integrated ferroelectrics as charge storage capacitors has increased dramatically not only for use in radiation hardened and commercial non-volatile memories, but also as possible high dielectric material suitable for capacitor applications. These properties combined with a thin film format, offer the capability of forming very compact capacitor structures suitable for MCM applications through Flip-Chip Bonding, or even integrated directly onto MMIC's. In this paper, the material PbZrxTi1-xO3, where x=l, 0.53, and 0.60 has been assessed. Thin films were produced using a sol-gel technique onto metallised thermally oxidised silicon. The effects on film microstructure and crystallinity with variation in the deposition process will be described. The best films were obtained by incorporating excess lead in the starting solutions, and also by the addition of acetylacetone which was used as a solution modifier. It will be demonstrated that fully perovskite films can be readily obtained at temperatures as low as 450°C. The films were normally 0.3-0.44μm thick with grain sizes of the order of 0.2μm. These films exhibited dielectric constants and loss in the range 170-800 and 1-3% respectively. Measurements upto 3MHz, indicated useful performance with low dispersion. The measured Pr and Ec were in the range 16-22μC/cm2, and 60-120kV/cm respectively.

PbTiO3(PT), Pb1-xLaxTi1-x/4O3(PLT) and PbZrxTi1-xO3(PZT) thin films were prepared by rf magnetron sputtering. It was found that the thin films have remarkably large pyroelectric effect and high figures of merit for infrared sensors without poling treatment. High performance pyroelectric infrared sensors (single element and linear array) were fabricated by using the PLT(x=0.1) thin films with the new structures and the device process. This type of sensor is carried on the air conditioner to detect a thermal environment. The PZT thin films with x=0.9 showed a large remanent polarization of 46μC/cm2 and small coercive force of 28kV/cm. In addition, good endurance behavior (no degradation of Pr after 1011 cycles) was observed. Recent activities of ferroelectric thin film research in Japan is also reported.

Ferroelectric lead zirconate titanate (PZT) films with a composition near the morphotropic phase boundary have been deposited by if magnetron sputtering on a Si substrate coated with silicon oxide, titanium, and platinum (Si/SiO2/Ti/Pt). Substrate temperature and oxygen partial pressure were changed during deposition to prepare films with controlled stoichiometry and perovskite structure. The effects of lead titanate (PT) as a buffer layer were investigated. Thin films of PT/PZT have a dielectric constant of 800 with a dissipation factor of 0.04 at 1 kHz. The remnant polarization of 8μC/cm2 and the coercive field of 50 kV/cm were measured. The effect of processing on the formation of perovskite phase and the electrical properties will be discussed.

In this work, a high-temperature deposition technique has been developed for ultra-thin sputtered PZT films for ULSI DRAM (<256Mb) storage capacitor applications. In contrast to the previously developed low-temperature (200°C) deposition, deposition at high-temperature (400°C) yields a desirable reduction in grain size of the perovskite phase. The thickness of PZT films has been reduced to less than 30nm with high charge storage density (∼30μC/cm2) and low leakage current density. An optimized 65nm PZT thin film was found to have an equivalent SiO2 thickness of 1.9Å and a leakage current density of less than 10−6 A/cm2 under 2V operation.

We have investigated the ablated flux characteristics of PbZrxTi1-xO3 as a function of deposition process parameters. The ablation-deposition rate, angular distribution, and type of ablated species axe all affected by the oxygen gas pressure. Visually, a change in the shape and color of the ablation plume are evident upon adding oxygen gas. The ablated flux distribution narrows as the oxygen pressure is increased, from a cos40θ distribution in a low gas pressure, up to a cos 260θ distribution at an oxygen pressure of 300 mTorr. This narrowing, or focusing, of the ablated plume also results in an increased deposition rate along the plume centerline for high laser power. However, at low laser power the deposition rate decreases as the pressure is increased, due to gas scattering effects. The energy of depositing species and the ratio of deposition flux to O2 flux will then be very different in each of these two regimes. The species in the plume have been examined using optical emission spectroscopy. We have found that mostly atomic species are present, but the ratio of ions to neutrals is very different for the Pb, Zr, and Ti atoms. Therefore, the application of electric fields near the substrate would affect the film composition to some degree.

SrTiO3 thin films were prepared by ECR and thermal MOCVD. In thermal-CVD mode, Sr content and Ti content were at a maximum at 0.56 Torr. Results showed that SrO deposition is a surface reaction limited process between 500 and 650°C, whereas TiO2 deposition is surface reaction limited between 500 and 600 °C, and diffusion limited above 600 °C. At a low pressure of 8 mTorr, ECR oxygen plasma was found to help decompose Ti(i-OC3H7)4. In ECR-CVD mode, the deposition temperature could be lowered to 400 °C. TEM and SEM analyses showed that SrTiO3 thin films have a columnar structure. The size of the grains depends on film thickness, and their shape on film composition (Sr/Ti ). Films prepared by thermal-CVD had a lateral step coverage of 50 %. 40 nm SrTiO3 thin films (Sr/Ti = 1.0) prepared by thermal-CVD on Pt/TaOx/Si and annealed for 2 hours in O2 had a maximum dielectric constant of 139 (Cs = 31 fF/μm2 and teq = 1.1 nm) and a leakage current density of 6x10−8 A/cm2 at 1.0 V.