Fabrication and characterization of Sr0.8Bi2.2Ta2O9 /Al2O3 gate stack for ferroelectric field effect transistors

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2021-02, Vol.127 (2), Article 107
• Main Authors: Kumar Jha, Rajesh, Singh, Prashant
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Annealing; Applied physics; Atomic layer epitaxy; Buffer layers; Characterization and Evaluation of Materials; Condensed Matter Physics; Electrical properties; Ellipsometry; Emission analysis; Ferroelectric materials; Ferroelectricity; Field effect transistors; Field emission microscopy; Grain size; Leakage current; Machines; Manufacturing; Materials science; Morphology; Nanotechnology; Optical and Electronic Materials; Perovskite structure; Perovskites; Physics; Physics and Astronomy; Process parameters; Processes; Read-write cycle; Refractivity; Semiconductor devices; Silicon; Silicon substrates; Surfaces and Interfaces; Thin Films; Transistors
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-021-04287-1

We analyze and report the structural, electrical and ferroelectric properties of Sr 0.8 Bi 2.2 Ta 2 O 9 /Al 2 O 3 /silicon gate stack for ferroelectric field effect transistors (FETs). RF sputtering and plasma-enhanced atomic layer deposition (PEALD) have been used for the deposition of Sr 0.8 Bi 2.2 Ta 2 O 9 (SBT) and Al 2 O 3 film, respectively. Different deposition and process parameters of the SBT and Al 2 O 3 films were optimized by obtaining the structural properties of the deposited film, and electrical properties of metal/ferroelectric/silicon (MFeS), metal/insulator/silicon (MIS), and metal/ferroelectric/metal (MFeM) structures. X-ray diffraction analysis reveals the polycrystalline perovskite structure of the SBT film having a dominant intensity peak along  direction at different annealing temperatures. Crystalline film morphology with a maximum grain size of 45 nm was confirmed at the annealing temperature of 500  ° C by the field emission scanning electron microscopy. Ellipsometric analysis of the SBT film reveals the maximum refractive index of 3.46 at the annealing temperature of 500  ° C. Introduction of a 10 nm buffer layer between ferroelectric and silicon substrate shows the improved memory window of 6.07 V in metal/ferroelectric/insulator/silicon (MFeIS) structure as compared to the 3.07 V in the MFeS structure. MFeI (10 nm) S structure also shows improved leakage current characteristics as compared to MFeS structures and endurance greater than 10 13 read/write cycles with the data retention time of higher than 10 years.