Structural and electrical properties of SrTiO₃ thin films as insulator of metal-ferroelectric-insulator-semiconductor (MFIS) structures

SrTiO₃ (STO) thin films were deposited on p-Si(100) substrates at various substrate temperatures from 300°C to 700°C by radio frequency (RF) magnetron sputtering technique. Their structure and electrical properties were investigated. It was found that the transition from amorphous phase to polycrystalline phase occurred at the substrate temperatures 300-400°C. Their crystallinity became better when the substrate temperatures further increased. The dielectric and leakage current measurements were carried out by using the Si/STO/Pt metal-insulator-semiconductor (MIS) structures at room temperature. It was found that the fixed charge density decreased and both the interface trap density and the dielectric constant increased when the substrate temperatures were increased. The leakage current mechanisms for STO MIS structures with STO films prepared at 700°C followed the space charge limited current (SCLC) under the low applied electric field and the Poole-Frenkel emission under the high one. In addition, the resistivity for films prepared at 700°C was higher than 10¹¹Ω.cm under the voltage lower than 10V (corresponding to the electric field of 1.54×10³kV.cm^-1). It suggested that the STO films prepared at 700°C were suitable for acting as the insulator of metal-ferroelectric-insulator-semiconductor (MFIS) structures.