Fabrication and characterization of ferroelectric Pb(Zr_xTi_1-x)O_3 thin films by metalorganic chemical vapor deposition

摘要

Ferroelectric Pb(Zr, Ti)O_3 (PZT) thin films were grown on Pt/Ti/SiO_2,/Si, RuO_2/Pt/Ti/SiO,/Si, and Pt/MgO substrates at the substrate temperature of 600 deg 'C by the metalorganic chemical vapor deposition (MOCVD) method. Pb(C_llH_l9O_2)_2(Pb(DPM)_2), Ti(OiC,H,)#, and Zr(O~t'C_4H_9)_4 as source material and Ar and O_2 as a carrier gas and oxidizing agent were selected, respectively. In order to investigate the effect of Zr and Ti component changes on the growth aspect of PZT thin films, Zr and Ti source materials were varied by controlling Zr and Ti flow rate. From the Rutherford backscattering spectroscopy (RBS) measurement, it was confirmed that the composition of the films, particularly Pb content, changed with the increasing Zr flow rate. In addition, the x-ray diffraction (XRD) spectra analysis showed the existence of a Pb-deficient pyrochlore phase as well as ZrO_2 as a secondary phase. From these results, it is believed that the higher Zr partial pressure in the gas phase reduces the sticking of the Pb precursor to the substrate. The film with Pb : Zr : Ti = l : 0.42 : 0.58 showed a dielectric constant of 8l6 at l MHz. The spontaneous polarization, remanent polarization, and coercive field measured from the RT66A by applying 3.5 V were 44.l mu C/cm~2, 24.4 pC/cm~2', and 59.6 kV/cm, respectively. The fatigue analysis of PZT thin films with Pb f Zr : Ti = 1 : 0.42 f 0.58 at an applied voltage of V_p-p = 5.4 V showed 40 degradation on the basis of initial polarization value after l09 cycles.