Misted Deposition of [3D] Trenches for Drams and Frams III. PZT Thin Films and PZT Nanotubes
Pb(Zr,Ti)O3 (PZT) thin films and nanotube were prepared on SiO2/Si substrates by liquid source misted chemical deposition (LSMCD) using Samco MD-6060 apparatus. We report the deposition and characterization of transparent ferroelectric thin films and nanotubes. PZT thin films deposited at ambient conditions and annealing at 700degC exhibit good ferroelectric properties with remanent polarisation of ca. 15 muC/cm2. The step coverage was 59% on the side wall and 79% on the bottom wall.
Fabrication of PZT Thin Films by Liquid Delivery MOCVD with Conventional Multi-Sources and a Novel Cocktail Source
Ferroelectric Pb(Zr,Ti)O3 (PZT) thin films were fabricated by liquid delivery MOCVD using conventional multi-sources. The deposition rate of 20 nm/min was attained at the reactor pressure of 5 Torr and the substrate temperature of 550°C by using Zr(DIBM)4 as a Zr-source instead of Zr(DPM)4. The step coverage increased from 50 to 100% by decreasing the substrate temperature from 600 to 400°C although the deposition rate decreased to the half. The uniform PZT thin films were successfully formed on 6-inch wafers. The variation in thickness was less than 5% all over the wafers. However, the remanent polarization at the center was half of that at the border. A cocktail source prepared by mixing Pb(METHD)2, Zr(METHD)4 and Ti(MPD)(METHD)2 with ECH was also examined. The cocktail source was stable for 3 months. PZT thin films deposited using the cocktail source exhibited ferroelectric properties. However, strongly oriented PbPtx alloy and oriented PbO were also formed. The improvement in crystallinity, electrical properties and surface morphology remains for future study.
Current Status of Bi-Based Precursors for Integrated Ferroelectrics
Two typical precursors for Bi4Ti3O12 thin films were analyzed spectroscopic methods and the local structure of those were chemically distinguished. Bi═Ti double alkoxide precursor containing Bi═O═Ti bonds promoted the homogeneous crystallization and was applicable to a series of Ca═Bi═Ti layer-structured ferroelectric thin films by addition of Ca ions. A hybrid precursor composed of Bi-triethylhexanoate and Ti-alkoxide needed the additional glass phase to suppress Bi2O3 segregation and resultantly, thinner Bi4Ti3O12 films with a thickness of 40 nm could be synthesized at 500°C and showed ferroelectricity.