Effect of (La, Sr)CoO3 seed layer on the reliability of Pb(Zr, Ti)O3 capacitors

Abstract

(La, Sr)CoO3(LSCO) thin layers have been grown on platinized Si substrates by pulsed laser deposition (PLD) to investigate the effects of LSCO as a seed layer for the formation of perovskite structure and the fatigue characteristics of Pb(Zr, Ti)O3(PZT) thin film capacitors. The thickness of the LSCO seed layer was varied in the range of 15 – 700 Å. It was found that PZT thin films with very thin (down to 15 Å) LSCO layer exhibited a single perovskite phase with (111) preferred orientation, while PZT thin films grown directly on Pt had a mixed phase of the perovskite and pyrochlore structures. This suggests that very thin LSCO layer is an effective seed layer for the formation of the perovskite phase. As the thickness of the LSCO layer increases, PZT thin films become randomly oriented with increasing the thickness of the LSCO layer. The greatly improved fatigue characteristics of the PZT films with the underlying LSCO layers were obtained irrespective of the LSCO thickness (15 – 700 Å). This was explained by the effect of conducting oxide layer (LSCO) as well as the orientation of PZT films on the fatigue characteristics. On the other hand, the fatigue of the PZT films with the top LSCO layer increased gradually with decreasing the top LSCO layer, in which case only the effect of the top LSCO layer could be considered because the orientation of the PZT films was kept the same.