Substrate orientation-induced device variation in HfO2-based 3D FeFETs

HfO2-based three-dimensional (3D) ferroelectric field-effect transistors (FeFETs) demonstrate great potential for ultra-high density memory applications. However, the device-to-device variation in threshold voltage (Vth) remains a challenge for their practical implementation. In this work, we systematically investigate the device-to-device variation induced by the variation of ferroelectric properties with the substrate orientation and potential mitigation approaches, an aspect that remains unexplored in HfO2-based 3D FeFETs. First, a device model incorporating randomly distributed nanoscale ferroelectric regions with distinct polarization magnitudes is developed. We reveal that the polarization disparities both among ferroelectric regions and between ferroelectric and non-ferroelectric regions have distinct effects on the device-to-device variation, and that these effects depend critically on the proportion of ferroelectric regions. Building on the inevitable presence of non-ferroelectric regions in the devices, we further explore variation mitigation strategies aimed at alleviating microscopic polarization non-uniformity through adjustments in device structures and operating conditions, such as employing a thicker oxide insulator or lowering the operating voltage. These results provide a theoretical foundation for optimizing the reliability of HfO2-based 3D FeFETs.