Ferroelectricity in Al2O3/Hf0.5Zr0.5O2 Bilayer Stack: Role of Dielectric Layer Thickness and Annealing Temperature

Abstract

In this paper, we investigate the ferroelectric properties of Al2O3/Hf0.5Zr0.5O2 (HZO) dielectric/ferroelectric (DE/FE) bilayer stack for different DE layer thickness and annealing temperature. The DE/FE stack showed enhanced remanent polarization (Pr) as compared to the reference HZO capacitor for very thin DE layer due to the charge induced by the leakage current through the DE layer. On the contrary, for higher DE layer thickness, this charge injection is suppressed and the ferroelectricity in the DE/FE stack reduces due to the involvement of the depolarization field. An increase in the coercive field (Ec) of the DE/FE based capacitors was observed with increasing the DE layer thickness. Moreover, the Pr value of both HZO and DE/FE stack increases with increasing the annealing temperature till 800 oC and decrease thereafter. The addition of Al2O3 layer increases the thermal stability of the capacitors and despite the HZO capacitors being degraded at annealing temperature beyond 800 oC, the DE/FE stack-based capacitors were found to demonstrate descent ferroelectricity.