Wolfgang Brand

Processing and electrical properties of Pb (ZrxTi1−x)O3 (x=0.2–0.75) films: Comparison of metallo‐organic decomposition and sol‐gel processes

The deposition of thin Pb(ZrxTi1−x)O3 films by sol‐gel and by metallo‐organic decomposition (MOD) processes has been studied. Powders obtained from different precursor solutions were analyzed with respect to their decomposition and crystallization. Using a spin‐coating technique, Pb(ZrxTi1−x)O3 films with zirconium concentrations ranging from x=0.2 to 0.75 have been deposited on Pt‐electroded Si wafers. The lattice constants of the perovskite films and their dielectric and ferroelectric properties (permittivity, remanent polarization, coercive field strength) have been measured as a function of the zirconium concentration. The results are compared to the data obtained on bulk ceramics. For Pb(ZrxTi1−x)O3 films with a composition located at the morphotropic phase boundary (x≊0.53) the influence of the processing and the lead excess of the starting solutions on the film properties was examined. First measurements on the resistance degradation of thin Pb(Zr0.53Ti47)O3 films deposited by the MOD process are r...

Materials for bulk acoustic wave (BAW) resonators and filters

Abstract Thin film bulk acoustic wave (BAW) resonators and filters are appropriate for mobile communication systems operating at high frequencies between 1–10 GHz. The resonance frequency is mainly determined by the thickness of the piezoelectric layer. Piezoelectric films used for this application are, therefore, several 100 nm in thickness (up to approx. 2 μm) depending on frequency. Piezoelectric thin film materials used for bulk acoustic wave devices include AlN, ZnO thin films for small bandwidth applications and also PZT films for wide bandwidth applications. Within Philips piezoelectric AlN and PbZr x Ti 1− x O 3 (PZT) layers are investigated with respect to their potential for RF micro-electronic applications. High quality AlN films with strong c -axis orientation are achieved by optimum sputter deposition conditions and by applying suited nucleation layers. Electromechanical coupling factors k of 0.25±0.03, which are close to the bulk data, have been found in highly c-axis oriented AlN thin films. The relationship between sputter deposition conditions, AlN films structure on the one hand and electromechanical coupling factor k and relevant electrical parameters on the other hand will be discussed. A one-dimensional physical model is used to describe the bulk acoustic wave resonators electrical impedance data accurately. Thin PZT films are grown via sol–gel processing. These films show high electromechanical coupling factor k of 0.3–0.6 and are therefore attractive for wide bandwidth filter applications.

Sol-gel, modified sol-gel, and metallo-organic decomposition techniques for complex oxide films: Materials processing and applications

Publisher Summary This chapter discusses the processing of thin oxide films via sol–gel, modified sol–gel, and metallo-organic decomposition (MOD). The special feature of sol–gel, modified sol–gel, and MOD processes is their low temperature depositions, which show more than 500 oC lower processing temperatures than the conventional ceramic sintering techniques and thus offer the compatibility of ceramic materials with substrates such as glass, glass-ceramic, and ceramic as well as silicon. The processing of thin films is relevant for microelectronic applications. These films include conductive oxides such as RuOx and dielectric thin films. Various types of precursor systems developed worldwide have been reported together with the growth of thin films and their typical performance. Dielectric films are developed for applications of thin film miniaturized capacitors, multifunctional modules, or ferroelectric nonvolatile memories. The relevance of these techniques for electroceramic films is demonstrated in the chapter in addition to the growth of thin films via different routes.

Filter system with bulk wave resonator having a reflection layer composition that varies with the layer thickness

The invention relates to a filter device equipped with at least one bulk acoustic wave resonator, which comprises a resonator unit and a reflection unit. The resonator unit comprises a first (3) and a second electrode (5) together with a textured piezoelectric layer (4) between the first (3) and second (5) electrodes.