Impact of Series-Connected Ferroelectric Capacitor in HfO₂-Based Ferroelectric Field-Effect Transistors for Memory Application

Wei-Dong Liu,Chun-Hu Cheng,Zhi-Wei Zheng,Jun Ma,Zi-You Huang

doi:10.1109/jeds.2020.3029268

Abstract

In this work, we demonstrated a HfO2-based ferroelectric field-effect transistor (FeFET) in series with a HfAlO ferroelectric capacitor for memory application and further investigated the impact of the ferroelectric capacitor with different thicknesses and areas. It was revealed that the memory window of the FeFET has a significant correlation with the ferroelectric capacitor from the transfer curves of the transistor after the series connection. By decreasing the thickness and area of the ferroelectric capacitor, the memory window of the FeFET was improved, which could be verified through the TCAD simulation tool and capacitance matching model. With the series-connected ferroelectric capacitor, in addition to optimizing the characteristics of ferroelectric memory, we can effectively avoid the interface-caused undesirable effects in conventional ferroelectric memory during film stacking. These results provide a solution for future low-power embedded memory application.

Highlights

Recently, ferroelectric materials have been widely investigated as gate dielectrics in ferroelectric field-effect transistors (FeFETs) due to the negative capacitance effect found in ferroelectric dielectrics [1]–[6]
The negative capacitance effect can break the physical limitation of Boltzmann tyranny leading to a sub-60mV/decade subthreshold swing (SS) under an ultralow supply voltage, which is critical for the application in Internet of Things (IoT) [7]–[9]
Since the memory window of conventional ferroelectric transistors with metal-ferroelectric-insulatorsemiconductor (MFIS) structure can be affected by the undesirable interface quality, such as interface defeats, leakage current and depolarization [12], the ferroelectric domain in material cannot do a stable switching, which results in the unexpected memory window during the operation of the FeFETs [5], [13]

Summary

Introduction

Ferroelectric materials have been widely investigated as gate dielectrics in ferroelectric field-effect transistors (FeFETs) due to the negative capacitance effect found in ferroelectric dielectrics [1]–[6]. Adding a ferroelectric layer into the gate stack of the metal-oxide-semiconductor field-effect transistors (MOSFETs) causes a unique operation behavior of the FeFETs, that is, there is a hysteresis loop in the transfer curve due to the polarization in ferroelectric material [11].

Results

Conclusion