| A significant amount of effort has been undertaken to develop new higher-dielectric constant materials to replace SiO2. Tantalum pentoxide is considered to be a promising choice for applications in DRAMs and CMOS logic devices, due to its high thermal stability, simple chemistry, and compatibility with current microelectronic fabrication processes. Literature reviews indicate a lack of information regarding the properties of Ta 2O5 in bulk form. This thesis is designed at providing new insights into the preparation and properties of Ta2O5-TiO 2 ceramics. The thermal behavior, phase stabilization, microstructure development, and, especially, dielectric properties for Ta2O 5-TiO2 ceramics are reported.; The thermal analysis of Ta2O5-TiO2 bulk ceramics formed by conventional mixed-oxide processing revealed unusual thermal behavior of competing densification and phase transformation proceed. The densification of these ceramics was shown to be impeded by a volume expansion from L-Ta2O5 to H-Ta2O5. SEM analysis for ceramics in the high-temperature phase showed a development of a lamellar-type microstructure, which appeared to extend over aligned regions referred to as “crystallographic orientations”. Electrical measurements for these ceramics exhibited strong dependencies of dielectric properties on both the structure and composition. Dielectric results and XRD data supported the conclusion that the stabilization of the high-temperature monoclinic phase of Ta2O5 at room temperature, led to an enhancement of the dielectric constant for Ta2O5-TiO2 ceramics. The highest value of K′ = 341 was determined in this thesis for a x = 0.056 composition. Comparison studies on dense Ta 2O5-TiO2 ceramics formed by hot pressing showed similar transformation characteristics and microstructure development. The dielectric properties was improved with increasing density.; A chemical-solution deposition method was used to integrate thin films of Ta2O5-TiO2 onto silicon substrates. Precursor solutions were successfully prepared using Ta(OEt)5 and Ti(OEt) 4 in ethanol. Solution stability was shown to be influenced by several factors, including, Rw ratio, additions of HCl, and, most importantly, conditions of hydrolysis. Electrical measurements revealed that amorphous films exhibited the most favorable dielectric properties, with low tanδ = 0.005 and K′ = 27. |
