Ferroelectric Sr2(Ta1-x,Nbx)2O7 with a Low Dielectric Constant by Plasma Physical Vapor Deposition and Oxygen Radical Treatment

The 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 and high heat-resistance. A very low dielectric constant ferroelectric Sr2(Ta1-x,Nbx)2O7 (STN) film formation technology which is applied to floating gate type ferroelectric random access memory (FFRAM) has been developed. The high ferroelectric performance of the STN capacitor has been achieved by plasma physical vapor deposition and an oxygen radical treatment using microwave-excited (2.45 GHz) high-density (>1012 cm-3) low electron temperature (<1 eV) Kr/O2 plasma.