Sr2(Ta, Nb)2O7 ferroelectric thin film for ferroelectric memory FET

Sr2Nb2O7 (SNO) family are suitable as ferroelectric materials for ferroelectric memory FETs, because they have low dielectric constant, low coercive field E c and high heat-resistance. In this study, we succeeded to prepare the Sr2(Ta, Nb)2O7 (STN) capacitors on the poly-Si. These capacitors were applied to FFRAM (Floating gate type Ferroelectric Random Access Memory) cells. The STN thin films were prepared by the sol-gel method. After several times spin coating and preannealing, these films were crystallized at about 950°C in oxygen for 30 sec by RTA (Rapid Thermal Annealing). When the Nb/(Ta+Nb) ratio was between 0.1 and 0.3, the ferroelectricities were confirmed. The maximum remanent polarization P r showed 0.4μC/cm2 when the ratio was 0.3. The FFRAM cell using STN thin films showed good memory characteristics.