| In this work, ferroelectric thin film capacitors for memories on semiconductors, such as Si and GaAs, using rf magnetron sputtering from a ferroelectric target, were fabricated. Different ferroelectric thin films, including barium titanate (BTO) and lead zirconate-titanate (PZT), were systematically studied as the dielectrics for the capacitor memories.; For the BTO thin film study, the structural, electrical, and ferroelectric properties were carried out on various structures, including metal-ferroelectric-metal, MFM, metal-ferroelectric-semiconductor Si, MFS(Si), and metal-ferroelectric-semiconductor GaAs, MFS(GaAS), by using different processing techniques. By taking advantage of the best properties from the different microstructures of BTO MFM capacitors, superior electric performance was achieved using a novel nanolayer structure, Au/amorphous-BTO/polycrystalline-BTO/microcrystalline-BTO/RuO{dollar}sb2{dollar}/Si. A very high dielectric constant, 259, was achieved while still maintaining the leakage current density of the capacitors in the range of 10{dollar}sp{lcub}-6{rcub}{dollar} A/cm{dollar}sp2{dollar} at a field strength of {dollar}1times10sp5{dollar} V/cm. The interface state density and oxide charge density were investigated on BTO films directly on semiconductors. A positive oxide charge density and interface state density in the range of {dollar}4.3times10sp{lcub}11{rcub}{dollar}/cm{dollar}sp2{dollar} and {dollar}9times10sp{lcub}11{rcub}{dollar}/cm{dollar}sp2{dollar}-eV, respectively, were obtained for BTO films directly on Si. For the PZT thin film study, a fairly high dielectric constant of about 548 was obtained with a Au/PZT/Pt/SiO{dollar}sb2{dollar}/Si structure, while the dielectric loss tan{dollar}delta{dollar} was measured to be less than 0.03. A remanent polarization of 30 {dollar}mu{dollar}C/cm{dollar}sp2{dollar} and a coercive field of 80 kV/cm were observed to confirm the ferroelectric properties of prepared PZT films.; The reliability of the ferroelectric thin films, which is another very important consideration for practical ferroelectric memories, was also studied through a thermal stability test, with more than 1000 hours of storage at 150{dollar}spcirc{dollar}C, and fatigue test, with 10{dollar}sp{lcub}12{rcub}{dollar} cycles. Less than 15% and 30% reductions of the fatigue characteristic was detected for BTO and PZT films, respectively. |
