No abstract

Pb(Zr0.53Ti0.47)O3 (PZT) films have been deposited on Pt/Ti/SiO2 and Pt/Ti/TiO2/polysilicon/ Si3N4/Si substrates. In the case of the Pt/Ti/TiO2/polysilicon/Si3N4/Si substrate, there are two different polycrystalline silicon layers. One has been postthermal annealed at 950°C for 30 min and the other has not had any thermal treatment after the deposition of the polycrystalline silicon. The hysteresis curve, piezoelectric coefficient (d 33) and dielectric constant of the as-grown film were measured to characterize the electrical properties. Wide angle X-ray diffraction patterns and cross-sectional images of the films were used to investigate the structural properties. The d 33 of the PZT thin film on substrate A, which was postannealed at 950°C for 30 min after deposition of polycrystalline silicon, was measured to be 158 pm/V by the single beam laser interferometer method. A low frequency relative dielectric constant was 829. Remanent polarization and coercive field of the film on the substrate A were 39.5 C/cm2 and 65.2 kV/cm, respectively. In addition, the interface of the PZT thin film on substrate A was more dense than that on substrate B, which was not postannealed after the deposition of polycrystalline silicon. This interface structure is very important during a chemical etching step. These results suggested that the substrate A is a very promising structure for microelectromechanical system devices based on the PZT thin film.

This paper analyses the problems posed by the interface structure during chemical etching by Hydro-fluoric (HF) acid for creating air gaps in microelectromechnical system (MEMS) devices using PZT(53/47) films and surface micromachining techniques. In order to investigate the influence of interface structure on the HF chemical etching process, Pt/PZT/Pt/Ti/TiO2/polysilicon/Si3N4/PSG/Si (Samples A and C) and Pt/PZT/RuO2/Ru/Si3N4/PSG/Si (Sample B) structures were fabricated. These structures are selected for a microcantilever beam and/or an uncooled IR detectors fabricated with PZT piezoelectric/pyroelectric films based on the surface micromachining technique. Both need etching for the removal of phosphor silicate glass (PSG) to create an air gap. If the devices had a poor interface structure, they would fail during the HF chemical etching process because the poor interface structure would act as a kind of penetration path for etching acid leading to unwanted etching. Therefore, it is very important to investigate the interface structure to fabricate efficient MEMS devices. In this study two different solutions have been suggested to improve the interface structure. The first is post thermal annealing at 900°C for 30 min. after deposition of polycrystalline silicon for sample A. Secondly, a RuO2/Ru hybrid electrode was deposited on Si3N4 directly instead of on the Pt/Ti/TiO2/Polysilicon electrode, which has Pt/PZT/RuO2/Ru/Si3N4/PSG/Si as the device structure. These two solutions suggest that a dense interface structure increases enhances of success of the chemical etching process of MEMS devices fabricated using PZT films and surface micromachining techniques.

1995) Influences of sol-GEL derived thin Pb(Zr 0.52Ti0.48 )O 3 layers as a buffer on RF sputtered Pb(Zr 0.52 Ti 0.48 )O 3 thin films,Abstract PZT(52/48) films are deposited by using an off-axis rf magnetron sputtering method on PtlTi/Si02/Si(100) substrate. In order to decrease the microcracks which occurs on the surface of rf sputtered PZT films during p s tannealing at 600,650 and 700"c, sol-gel derived 10% Pb excess Pb(Zro.52T&.48)03 layers are placed at the top and bottom of the rf sputtered PZT films, respectively. SEM micrographs reveal a drastic reduction of microcracks on the surface of the buffered PZT films. In addition, enhancement of crystallinity is also observed according to XRD analysis. The P-E hysteresis measurements show an increase in remanent polarization (12.3, 22.45, 34.64 p C/cm2) and a decrease of the coercive field (108, 72.9, 68.3 kV/cm) with the increase of post-annealing temperature.