Insertion of HfO2 Seed/Dielectric Layer to the Ferroelectric HZO Films for Heightened Remanent Polarization in MFM Capacitors

This article highlights the role of HfO
₂
seed/dielectric insertion layers on the ferroelectric properties of hafnium zirconium oxide (HZO)-based metal-ferroelectric-metal (MFM) capacitors. Maximum remanent polarization (Pr) of 22.1 μC/cm
²
was achieved when HfO
₂
seed layer of critical thickness (10 Å) was inserted at the bottom of HZO films. However, as the bottom HfO
₂
seed layer thickness increases from 10 to 200 Å, the Pr was found to decrease. The same critical thickness of HfO
₂
seed layer when inserted at top of the HZO films was found to give a maximum Pr of 19.6 μC/cm
²
. The obtained Pr in both the cases (bottom and top HfO
₂
seed layer) was found to be better than the reference HZO device (17.7 μC/cm
²
). Moreover, increased coercive field (E
_c
) was noticed due to the HfO
₂
seed layer insertion (1.11 MV/cm for bottom HfO
₂
and 1.09 MV/cm for top HfO
₂
) when compared with the reference device (1.04 MV/cm). Short pulse switching measurements were carried out on the as-fabricated capacitors, and an enhanced E
_c
and interfacial capacitance was observed in case of devices with HfO
₂
seed layer. The crystal structures, and interfacial layer effect was keenly observed and analyzed for the HZO films with and without the seed layer using grazing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS), respectively. The HfO
₂
seed layer was found to result in higher o-phase formation, and facilitates the diffusion/migration of oxygen atoms from seed layer to the substrate or vice versa in the HZO capacitors giving rise to enhanced ferroelectricity.