R&D: Metal (Pt)/Ferroelectric (SrBi2Ta2O9)/Insulator (La2O3)/Semiconductor (Si), MFIS Structures for Nonvolatile Memory Applications

Applied Physics Letters has published an article written by Shivendra K. Rathaur, School of Computing and Electrical Engineering, Indian Institute of Technology (IIT)-Mandi, Mandi 175075, Himachal Pradesh, India, and , Department of Electrical Engineering, Indian Institute of Technology (IIT)-Delhi, Delhi 110016, India, Robin Khosla, School of Computing and Electrical Engineering, Indian Institute of Technology (IIT)-Mandi, Mandi 175075, Himachal Pradesh, India, Institute of Semiconductor Engineering, University of Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart, Germany, and Department of Electronics and Communications Engineering, National Institute of Technology (NIT), Silchar, Assam 788010, India, and Satinder K. Sharma, School of Computing and Electrical Engineering, Indian Institute of Technology (IIT)-Mandi, Mandi 175075, Himachal Pradesh, India.

Abstract: “Extended data retention is a cardinal impediment for ferroelectric memories and serves a pivotal role for nonvolatile memory applications. Here, nonvolatile Metal–Ferroelectric–Insulator–Semiconductor (MFIS) structures are fabricated by using thin films of Strontium Bismuth Tantalum Oxide (SrBi₂Ta₂O₉) as ferroelectric and high-κ lanthanum oxide (La₂O₃) as a buffer insulator on p-Si substrates via RF magnetron sputtering. The grazing incidence x-ray diffraction analysis confirms the dominant (111) and (115) ferroelectric perovskite phases of SrBi₂Ta₂O₉ thin films. Albeit, atomic force microscopy surface micrographs revealed highly smooth La₂O₃ and SBT (SrBi₂Ta₂O₉) thin films with a surface roughness of ∼0.22 ± 0.04 nm and ∼1.05 ± 0.03 nm, respectively. Capacitance–voltage (C–V), capacitance–time (C–T), and current–voltage (I–V) characteristics of Pt/SrBi₂Ta₂O₉/La₂O₃/Si, MFIS structures, exhibited a high memory window of ∼1.1 V at ±5 V sweep voltage, data retention measured until ∼10⁴ s even on the extrapolation up to 10 years, and a low leakage current density of ∼12.8 μA/cm² at −1 V and 300 K. Far from it, the probed conduction mechanism is studied for Pt/SrBi₂Ta₂O₉/La₂O₃/Si MFIS device structures. The optimum nonvolatile memory characteristics are attributed to the high-quality SBT ferroelectric and the buffer layer La₂O₃/Si interface of the investigated MFIS structure and also assert from the control Pt/SBT/Pt and Pt/La₂O₃/Si results. Thus, the proposed Pt/SrBi₂Ta₂O₉/La₂O₃/Si structure is a potential candidate for a gate stack of one-transistor (1T) type Ferroelectric Field-Effect Transistors nonvolatile memory applications.“