Impact of HfO2 buffer layer on the electrical characteristics of ferroelectric/high-k gate stack for nonvolatile memory applications

Abstract

For the proposed work, the electrical properties of metal–ferroelectric–insulator–silicon (MFeIS) capacitors with Sr0.8Bi2.2Ta2O9 (SBT) ferroelectric film deposited on HfO2/Si substrate have been investigated. The SBT film was deposited by RF sputtering and HfO2 film by plasma-enhanced atomic layer deposition (PEALD). The structural characteristic of the deposited ferroelectric and dielectric films was obtained using X-ray diffraction and multiple angle ellipsometric analysis. XRD results indicate the polycrystalline and perovskite structure of the SBT film and amorphous structure of the HfO2 film annealed at different temperatures. SBT film deposited on the silicon substrate and annealed at 500 °C shows the maximum refractive index of 3.46 with the maximum grain size of 32 nm. Metal/ferroelectric/silicon (MFeS), metal/ferroelectric/metal (MFeM), metal/insulator/silicon (MIS) and metal/ferroelectric/insulator/silicon (MFeIS) structures were fabricated to obtain the electrical and ferroelectric properties. MFeIS structure with 10 nm buffer layer shows the improved memory window of 5 V as compared to the 3.07 V in the MFeS structures. MFeI(10 nm)S structure even shows endurance higher than 1012 read/write cycles and data retention for more than 8 h.