Recent Progress of Ferroelectric-Gate Field-Effect Transistors and Applications to Nonvolatile Logic and FeNAND Flash Memory

Shigeki Sakai,Mitsue Takahashi

doi:10.3390/ma3114950

Abstract

We have investigated ferroelectric-gate field-effect transistors (FeFETs) with Pt/SrBi2Ta2O9/(HfO2)x(Al2O3)1−x (Hf-Al-O) and Pt/SrBi2Ta2O9/HfO2 gate stacks. The fabricated FeFETs have excellent data retention characteristics: The drain current ratio between the on- and off-states of a FeFET was more than 2 × 106 after 12 days, and the decreasing rate of this ratio was so small that the extrapolated drain current ratio after 10 years is larger than 1 × 105. A fabricated self-aligned gate Pt/SrBi2Ta2O9/Hf-Al-O/Si FET revealed a sufficiently large drain current ratio of 2.4 × 105 after 33.5 day, which is 6.5 × 104 after 10 years by extrapolation. The developed FeFETs also revealed stable retention characteristics at an elevated temperature up to 120 °C and had small transistor threshold voltage (Vth) distribution. The Vth can be adjusted by controlling channel impurity densities for both n-channel and p-channel FeFETs. These performances are now suitable to integrated circuit application with nonvolatile functions. Fundamental properties for the applications to ferroelectric-CMOS nonvolatile logic-circuits and to ferroelectric-NAND flash memories are demonstrated.

Highlights

As a nonvolatile memory, ferroelectric-gate field-effect-transistors (FeFETs) have many advantages in high-density integration, low power dissipation, non-destructive readout operation, and good scalability [1]
A promising gate-material combination of metal/ferroelectric/insulator/semiconductor (MFIS) and a good process for FeFETs having long data retention were found by the author (S.S.) in 2002 [13,14,15,16,17,18]
Note that FeFETs based on different materials and on different types have been investigated during the last decade, which are listed only partially in [19,20,21,22,23,24,25,26]

Summary

Introduction

Ferroelectric-gate field-effect-transistors (FeFETs) have many advantages in high-density integration, low power dissipation, non-destructive readout operation, and good scalability [1]. A promising gate-material combination of metal/ferroelectric/insulator/semiconductor (MFIS) and a good process for FeFETs having long data retention were found by the author (S.S.) in 2002 [13,14,15,16,17,18]. We are investigating two kinds of applications of the FeFETs, which are FeCMOS nonvolatile logic circuits and FeNAND flash memories. We will first describe our FeFET development, and second, we will show recent results of the FeFET applications to FeCMOS and FeNAND flash memories

Progress of Ferroelectric-Gate Field-Effect-Transistors

FeCMOS Nonvolatile Logic Circuits

FeNAND Flash Memory

Conclusions