Enhanced thermal robustness of laminated Hf0.5Zr0.5O2 ferroelectric film via Al2O3 mid-layer engineering

초록

This work investigates the role of an Al2O3 (AO) mid-layer embedded in Hf0.5Zr0.5O2 (HZO) film under high thermal budget conditions (-1000 degrees C). The AO mid-layer suppresses grain growth and inhibits monoclinic phase (m-phase) formation. In addition, Al diffusion from the AO mid-layer into the HZO during high temperature annealing acts as an effective ferroelectric dopant, further stabilizing the ferroelectric orthorhombic phase (ophase). The diffused Al also reduces oxygen diffusivity of HZO film and suppresses the formation of a TiOxNy dead layer at the HZO/TiN interface. As a result, the AO-integrated HZO film (w/ AO) exhibits a reduction in leakage current by three orders of magnitude compared to the film without the AO mid-layer (w/o AO). The w/ AO sample achieves an enhanced remanent polarization (Pr) of 22.2 mu C/cm2 and a reduced coercive voltage (Vc) of 2.70 V after annealing at 1000 degrees C, whereas the w/o AO sample shows degraded values (Pr of 16.9 mu C/cm2 and Vc of 3.46 V). Furthermore, the w/ AO sample exhibits improved switching characteristics without premature dielectric breakdown. These results confirm that AO mid-layer engineering is an effective strategy for achieving thermally robust ferroelectricity, enabling reliable integration of HZO-based devices into high thermal budget processes.

키워드