Structural and electrical properties of metal-ferroelectric-insulator-semiconductor transistors using a Pt/Bi_(3.25)Nd_(0.75)Ti_3O_(12)/Y_2O_3/Si structure

摘要

The metal-ferroelectric-insulator-semiconductor (MFIS) capacitors were fabricated using the Pt/Bi_(3.25)Nd_(0.75)Ti_3O_(12)/Y_2O_3/Si(100) 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(100) at room temperature by electron-beam evaporation method. Nd-modified bismuth titanate (Bi_(3.25)Nd_(0.75)-Ti_3O_(12):BNT) films were prepared as ferroelectric layers at a processing temperature of 750℃ 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(100) 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 x 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(100) 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.