Retentivity Studies on Lead Zirconate Titanate Thin Film Capacitors

Abstract

AbstractRetention characteristics of various ferroelectric memory cell structures, based on lead zirconate titanate (PZT) capacitors, were investigated under different test conditions. Test of retentivity without any pre-treatment, revealed very high rates of polarization loss with time for partially polarized PZT capacitors. However, when different structures were subjected to a thermal cycle before retentivity study, they indicated significant polarization loss or polarization reversal in FRAM and MFMIS(metal-ferroelectric-metal-insulatorsemiconductor) structures. This thermal cycle dependent retentivity problem was attribute to pyroelectric charges that are developed during the temperature cycle.For each memory cell structure, the underlying mechanisms for the rapid polarization. loss were discussed. Furthermore, guidelines for improving the memory retention were proposed based on the theoretical interpretation of the phenomena.