SRBI2TA2O9 THIN-FILMS MADE BY LIQUID SOURCE METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION

A liquid source metal-organic chemical vapor deposition system was ins talled to deposit SrBi2Ta2O9 (SET) thin films on sapphire and Pt/Ti/Si O2/Si substrates. The process parameters such as deposition temperatur e and pressure, and ratio of Sr:Bi:Ta in the precursor solutions were optimized to achieve stoichiometric films with good reproducible ferro electric properties. It was found that the nucleation of SET started a t a deposition temperature close to 500 degrees C and grain growth dom inated at 700 degrees C and higher temperatures. With increasing depos ition temperatures, the grain size of SET thin films increased from 0. 01 mu m to 0.2 mu m; however, the surface roughness and porosity of th e films also increased. To fabricate specular SET films, the films had to be deposited at lower temperature and annealed at higher temperatu re for grain growth. A two-step deposition process was developed which resulted in high quality films in terms of uniformity, surface morpho logy, and ferroelectric properties. The key to the success of this pro cess was the homogeneous nucleation sites at lower deposition temperat ure during the first step and subsequent dense film growth at higher t emperature. The two-step deposition process resulted in dense, homogen eous films with less surface roughness and improved ferroelectric prop erties. SET thin films with a grain size of about 0.1 mu m exhibited t he following properties: thickness: 0.16-0.19 mu m; 2P(r): 7.8-11.4 mu C/cm(2) at 5 V; E(c): 50-65 kV/cm; I-leakage: 8.0-9.5 x 10(-9) A cm(- 2) at 150 kV/cm; dielectric constant: 100-200; and fatigue rate: 0.94- 0.98 after 10(10) cycles at 5 V.