Properties of Sr2Nb2O7 family ferroelectric thin films

Sr₂Nb₂O₇ (SNO) family are suitable for use as ferroelectric materials for ferroelectric memory field effect transistor (FET)s, because these substances have a low dielectric constant, low coercive field and high heat resistance. In this study, we succeeded in operating Sr₂(Ta,Nb)₂O ₇ (STN) capacitors on polycrystalline silicon (poly-Si). From secondary ion mass spectroscopy (SIMS) profiles, no-interdiffusion in the STN metal ferroelectric metal insulator semiconductor (MFMIS) structure was confirmed. C-V and I_D-V_G hysteresis curves which were dependent on ferroelectric polarization were obtained. These capacitors were applied to floating gate type ferroelectric random access memory (FFRAM) cells. The degradation in ferroelectricity of STN capacitors during FFRAM cell fabrication process was not observed. We succeeded in operating FFRAM cells with a lower voltage than that required for PZT