Impact of HfO2 buffer layers on data retention characteristics of ferroelectric-gate field-effect transistors

Abstract

Electrical properties of the $p$ -channel metal-ferroelectric-insulator-silicon field-effect transistors (MFISFETs) using $\mathrm{Pt}∕{\mathrm{SrBi}}_2{\mathrm{Ta}}_2{\mathrm{O}}_9\left(\mathrm{SBT}\right)∕{\mathrm{HfO}}_2∕\mathrm{Si}$ and $\mathrm{Pt}∕{(\mathrm{Bi},\mathrm{La})}_4{\mathrm{Ti}}_3{\mathrm{O}}_{12}\left(\mathrm{BLT}\right)∕{\mathrm{HfO}}_2∕\mathrm{Si}$ gate structures were investigated. Sol-gel-derived 400-nm-thick SBT and BLT films were deposited on an ${\mathrm{HfO}}_2$ film of approximately 10 nm in thickness. The channel width and channel length of the fabricated MFISFETs were 50 and 5 μm, respectively. The significant drain current on∕off ratios were retained for over 10 days at room temperature. The fabricated MFISFETs using a $\mathrm{Pt}∕\mathrm{SBT}∕{\mathrm{HfO}}_2∕\mathrm{Si}$ gate structure exhibited a drain current on∕off ratio of about ${10}^5$ even after 15.9 days had elapsed. It was also found in the fabricated MFISFETs that a write pulse width as short as 20 ns was enough for obtaining the significant drain current on∕off ratio. It is concluded from these results that ${\mathrm{HfO}}_2$ is one of the best buffer layer materials for realizing MFISFETs with long data retention and high operation speed.