Comparison of hafnia and PZT based ferroelectrics for future non-volatile FRAM applications

Abstract

Ferroelectric random access memories (FRAM) are nonvolatile memories which allow a fast access time and a low power consumption. State-of-the-art devices are based on the perovskite lead zirconate titanate (PZT), which suffers from CMOS incompatibility resulting in scaling issues. The discovery of the ferroelectricity in doped hafnium oxide enabled scaled 3D memory devices. A variety of dopants has already been found to stabilize the orthorhombic phase, responsible for ferroelectric switching. Interestingly, among the variety of dopants only a mixed hafnium zirconium oxide (HZO) enabled a wide process window together with a large memory window. Here, we compare PZT with HZO and show that despite different dielectric properties similar memory relevant performance can be achieved. Additionally, analogous wake-up and degradation behavior can be observed in both materials. Moreover, we show experimental proof that a thermally driven wake-up in both material systems is caused by diffusion of ionic charges. Extracted activation energy hints to oxygen vacancy movement as the main cause for the wake-up effect in HZO.