Structural and electrical properties of metal-ferroelectric-insulator–semiconductor transistors using a Pt/Bi 3.25Nd 0.75Ti 3O 12/Y 2O 3/Si structure

Abstract

The metal-ferroelectric-insulator–semiconductor (MFIS) capacitors were fabricated using the Pt/Bi 3.25Nd 0.75Ti 3O 12/Y 2O 3/Si(1 0 0) structure, yttrium sesquioxide (Y 2O 3) thin films as an insulating buffer layer with different thickness ranging from 10 to 40 nm were deposited on p-type Si(1 0 0) at room temperature by electron-beam evaporation method. Nd-modified bismuth titanate (Bi 3.25Nd 0.75Ti 3O 12:BNT) films were prepared as ferroelectric layers at a processing temperature of 750 °C by chemical solution deposition (CSD) method. The Y 2O 3 buffer layers show an amorphous structure, relatively high dielectric constant, and good electrical properties. The ferroelectric polarization–voltage ( P– V) hysteresis was observed for Pt/BNT/Pt/Ti/SiO 2/Si and Pt/BNT/Y 2O 3/Si(1 0 0) capacitors. The MFIS structure exhibits a larger clockwise C– V memory window of 2.63 V when the thickness of Y 2O 3 layer was 10 nm and a lower leakage current density of 7 × 10 −9 A/cm 2 at a positive applied voltage of 6 V. Capacitance–voltage ( C– V) and leakage–current density ( J– V) characteristics of Pt/BNT/Y 2O 3/Si(1 0 0) capacitor indicate that the introduction of the Y 2O 3 buffer layer prevents the interfacial diffusion between BNT thin film and the Si substrate effectively and improves the interface quality. Furthermore, the Pt/BNT/Y 2O 3/Si structures exhibit excellent retention characteristics, the high and low capacitance values biased in the hysteresis loop are clearly distinguishable for over 13.6 days. The experimental results show that the BNT-based MFIS structure is suitable for non-volatile ferroelectric memory field-effect-transistors (FETs) with large memory window.