THE MICROSTRUCTURE AND PROPERTIES OF LAYERED OXIDE THIN FILMS FABRICATED BY MOCVD

摘要

For the first time, layered oxide thin films of SrBi_2Ta_2O_9 (SBT) with very good ferroelectric properties have been prepared by direct-liquid-injection MOCVD technique. The SBT films were deposited onto both Pt/Ti/SiO_2/Si wafers and single-crystal sapphire substrates to measure their phase formation, microstructure and ferroelectric properties. Crystalline SBT phase had been observed at temperatures as low as 500 deg C. With increasing deposition temperature above 500 deg C, the grain size of SBT thin films was increased from 0.01 #mu#m to 0.2 #mu#m. The films were found to be dense and homogenous. Typically, SBT thin films of 200 nm thick with grain size about 0.1 #mu#m have 2Pr around 10 #mu#C/cm~2 at 5V, Ec 55.7 kV/cm, and dielectric constant around 100. The leakage currents were as low as 8 X 10~(-9) A/cm~2 at 150 kV/cm. The films also showed fatigue-free characteristics: no fatigue was observed up to 1.4 X 10~(10) switching cycles. This development of MOCVD technique for good quality SBT films make their integration into high density nonvolatile memories relatively easy.