Developmental Research on Large Area Growth of Ferroelectric Thin Films with a High Growth Rate by MOCVD and Their Applications to Memory Device

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A 6-8 inch single wafer type MOCVD system for ferroelectric thin films was developed. Large area growth of Pb (Zr, Ti) 03 (PZT) and (Pb, La) (Zr, Ti) 03 (PLZT) thin films was performed by MOCVD on a 6-8 inch Si wafer. Highly uniform PZT thin films with a variation in film thickness of less than <plus-minus>1.2% were successfu lly grown on a 6-8 inch wafer. The variations in the Pb, Zr and Ti components were of less than <plus-minus>0.8, <plus-minus>0.8 and <plus-minus>1.1%, respectively. PZT films with variation in dielectric constant of less than <plus-minus>5.1% were also obtained on a 6 inch wafer. On a 6 inch wafer. PLZT films with a variation in film thickness of less than <plus-minus>1.5% were also grown. The growth rate of PZT and PLZT films was 30-40/min, which was not enough for the realization of the practical production of memory devices. In order to obtain the high growth rate, an improvement in the shape of gas nozzle shouldThe electrical properties of PZT thin films grown on Ir, IrO_2 and Ir/IrO_2 bottom electrodes and the effects of various top electrode materials on the electrical properties of these PZT films were investigated. The PZT thin film capacitors using Ir and IrO_2 electrodes showed no fatigue up to a switching cycle of 10^<11>. It was also found that annealing process after forming the upper electrode was one of key factors in determining the fatigue characteristics.