Properties of Ferroelectric Memory FET Using Sr2(Ta, Nb)2O7 Thin Film

Abstract

Compounds of the Sr2Nb2O7 (SNO) family are suitable for use as ferroelectric materials for ferroelectric memory field effect transistors (FETs), because these substances have a low dielectric constant, low coercive field and high heat resistance. C–V and ID–VG hysteresis curves which depend on ferroelectric polarization were obtained. These capacitors were applied to floating gate ferroelectric random access memory (FFRAM) cells. The degradation in the ferroelectricity of STN capacitors was not observed during the fabrication of FFRAM cells. We succeeded in operating FFRAM cells at a lower voltage than that required for PZT. Data retention characteristics of metal ferroelectric metal insulator semiconductor (MFMIS) structures with STN films were first measured to be up to 2 weeks. Data retention is close related to be the leakage current of the ferroelectric. The MFMIS FET has the potential to retain data for 10 years.