Experimental Investigation of Variations in Polycrystalline Hf0.5Zr0.5O2 (HZO)-based MFIM

Device-to-device variations in ferroelectric (FE) hafnium oxide-based devices pose a crucial challenge that limits the otherwise promising capabilities of this technology. Earlier simulation-based studies have identified polarization (P) domain nucleation and polycrystallinity as key contributors to these variations. In this work, we experimentally investigate the effect of these two factors on remanent polarization (PR) variation in Hf0.5Zr0.5O2 (HZO) based metal-ferroelectric-insulator-metal (MFIM) capacitors for different set voltages (VSET) and FE thicknesses (TFE). Our measurements reveal a non-monotonic behavior of PR variations with VSET, which is consistent with previous simulation-based predictions. For low and high-VSET regions, we find that PR variations are dictated primarily by saturation polarization (PS) variations and are associated with the polycrystallinity in HZO. Our measurements also reveal that PR variations peak near the coercive voltage (VC), defined as the mid-VSET region. We attribute the increase of PR variation around VC to the random nature and sharp P switching associated with domain nucleation, which is dominant near VC. Further, we observe a reduction in the peak PR variation as HZO thickness (TFE) is scaled. We validate our arguments by establishing the correlation between the measured values of PR with VC and PS. Our results display that a strong correlation exists between PR and VC in the mid-VSET region and between PR and PS in the low and high-VSET regions across various TFE.