Development of MFMIS Gatestack with Thick Hafnium Zirconium Oxide (HZO) for Nonvolatile Memory Application

In this work, a thick HZO-based gate device is examined for memory applications owing to its wider memory window. The TiN - HZO- TiN film layers are demonstrated by measuring electrical properties such as polarization, capacitance, and current. In addition, to apply a thick HZO stack to an integrated memory device, we develop an MFMIS etching process and define a gate structure with a sufficient memory window of 4 V.

Introduction

Despite the introduction of a high-k dielectric on the 45 nm technology node [1], CMOS devices require another solution for further scaling. Thus, a new ferroelectric device with a different concept is required. Generally, ferroelectric devices can be used as nonvolatile memories, utilizing hysteresis characteristics and super steep sub-threshold swing [2], [3]. Hafnium Zirconium oxide (HZO) is a promising ferroelectric material based on Hf0₂, which is commonly used in the industry [1]. In many studies [4]–[6], thin HZO has been used in gatestacks to secure vertical integration with limited spacing. Meanwhile, to apply the HZO gatestack to a memory system, a suitable process for integration must be developed to be integrated into the circuit.