Fabrication of PZT thin films using digital-MOCVD method and its application for electronic devices

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Recently, ferroelectric thin films such as Lead based perovskite structure have been actively studied as one of the promising materials for capacitor dielectric films in dynamic random-access memories (DRAMs) and ferroelectric random-access memories (FeRAMs), and for gate insulators in ferroelectric-gate FETs with metal-ferroelectric-semiconductor (MFS) gate structure. In particular, MFS-FET is expected to be one of the leading candidates for the future memory devices because of its non-volatility, high switching speed, high integration without storage capacitors, and so on. However, there have been few satisfactory results regarding fabrication of ferroelectric thin films directly on Si substrates, because there have been difficulties in the formation of ferroelectric/Si interfaces due to interdiffusions and lattice mismatches between them. ln this research. Pb(Zr, Ti)O_3 (PZT)/MgO/Si(0O1) stacked structure, which is one of the principle components of ferroelectric-gate FETs, has been fabricated and characterized. Using both the theta-2theta and the 2-dimensional X-ray diffraction (XRD) method, the fully epitaxial relationship of PZT[100]//MgO[100]//Si[110] has been confirmed in the PZT(001)/MgO(001)/Si(001) stacked structure fabricated with the maximum processing temperature of 480ﾟC.The fully epitaxial relationship causes no affection on the electrical properties of PZT and Si. Especially for MgO/Si interfaces, itwould make possible to control the surface potential of Si by the gate voltages in ferroelectric-gate FETs.