Low Voltage Performance in Lead Based Ferroelectric Thin Film Memory Elements with (La,Sr)CoO3 Electrodes

Abstract

Realization of a commercially viable ferroelectric memory technology has been hampered by one or a combination of problems related to either the reliable performance of the ferroelectric capacitor or to the growth and processing of capacitors that translate to high density memory elements. Issues related to the growth and processing of ferroelectric capacitors have already been discussed at least in part, in earlier chapters. Prior to discussing the reliability issues, a comment on the ferroelectric material is warranted. Currently, there is some debate regarding the choice of ferroelectric material and their associated merits and disadvantages. The two materials of choice are doped or undoped lead zirconate titanate [PZT] and SrBi2Ta2O9. We believe that PZT is the better choice primarily due to the temperature restrictions in Si-CMOS technology and therefore the discussion in this chapter is limited to PZT. We discuss issues related to the reliable performance of lead zirconate titanate [PZT] and cationically substituted derivatives (Pb,La)(Zr,Ti)O3 [PLZT], Pb(Zr,Ti,Nb)O3 [PNZT] ferroelectric capacitors. In recent years, it has become clear that the choice of electrode material is very crucial in determining the reliability characteristics of ferroelectric capacitors. Different electrode materials that may be used in conjunction with lead based ferroelectric thin films for non-volatile memory applications have been briefly discussed in an earlier chapter (by Bruce Tuttle). In the following, some of the requirements for a material to be used as an electrode are emphasized.