A Fatigue-Tolerant Metal-Ferroelectric-Oxide-Semiconductor Structure with Large Memory Window Using Sr-deficient and Bi-excess Sr0.7Bi2+yTa2O9 Ferroelectric Films Prepared on SiO2/Si at Low Temperature by Pulsed Laser Deposition

Abstract

Preferentially (105)-oriented Sr_0.7Bi_2.8Ta₂O₉(SBTO) thin films on SiO₂/n-Si(100) have been prepared by a pulsed laser deposition method at temperatures as low as 350°C, which is the lowest process temperature for growing SBTO ferroelectric thin films. Dielectric properties of SBTO films have been improved by increasing the Sr/Bi atomic ratio from 0.7/2.8 to 0.7/2.0. A memory window as large as 3.6 V in the Metal-Ferroelectric-Insulator-Semiconductor(MFIS) capacitor has been obtained at a Sr/Bi ratio of 0.7/2.0. This is the largest value among the MF(I)S diode structures. Little degradations in C-V are observed up to fatigue of over 10¹⁰ cycles for a process temperature of 400°C, or especially for Sr/Bi of 0.7/2.0, keeping the memory window at more than 3.2 V. It should be emphasized that improvement in memory characteristics is strongly related to the insulating properties of the ferroelectric and dielectric thin films rather than to the value of the dielectric constant.