Recent Developments on MOCVD of Ferroelectric Thin Films

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Ferroelectric Pb(Zr, Ti)O3 thin films were fabricated by liquid delivery MOCVD using Pb(DPM)2, Ti(OiPr)2(DPM)2 and Zr(DIBM)4. The deposition rate of 12.3 nm/min was attained on 6-inch Pt/Ti/SiO2/Si wafers at 550°C. The average and the deviation of twofold remanent polarization were 45.5 μC/cm2 and ± 6.4%, respectively, over the 6-inch wafer. Step coverage was improved from 44% to 90% by decreasing deposition temperature from 550 to 400°C although the deposition rate decreased by 60%. TiO2 nanoparticles diffused to the surface of platinum bottom electrodes were effective as a seed to obtain 111 preferential oriented PZT thin films at the deposition temperature of 550°C. Iridium oxide bottom electrodes were reduced to metal ones by CO and/or H2 gases generated by decomposition of precursors. Oxide materials seem to be not the best as bottom electrodes in liquid delivery MOCVD. A cocktail source consisted of Pb(METHD)2, Ti(MPD)(METHD)2 and Zr(METHD)4 was also examined. PbPtx alloy phase existed in PZT films deposited at 500°C was disappeared by post-annealing at 600°C and the annealed film showed hysteresis properties with the 2Pr of 56 μC/cm2 and the 2Ec of 181 kV/cm.

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