Growth of the orthorhombic phase and inhibition of charge injection in ferroelectric HfO2-based MFIS memory devices with a high-permittivity dielectric seed layer

Abstract

The poor endurance of the ferroelectric (FE) HfO2 (Fe-HfO2) material-based FE field-effect transistor (Fe-FET) remains a major challenge for its future commercial production. Here we propose a high-κ interface seed layer (SL) in the metal-FE-insulator-semiconductor (MFIS) gate stack to address this issue. We fabricated Hf0.5Zr0.5O2 (HZO) FE thin films on various high-κ dielectric SLs, including ZrO2, HfO2, (HfO2)0.75(Al2O3)0.25 (HAO), and Al2O3, and investigated their microstructures, ferroelectricity, and memory characteristics in the MFIS devices. The results show that the nucleation and growth of the FE orthorhombic phase in HZO films are affected not only by the surface energy but also by the microstructure of the high-κ SL. Additionally, we clarified the role of the high-κ SL on the memory characteristics of the MFIS devices, which were reasonably explained by the accurately calculated interface electric field. Finally, we realized a good tradeoff between the FE polarization and interface charge injection in the MFIS device with HAO high-κ SL, demonstrating a large FE window (> 1.0 V), excellent retention (> 1.6×104 s), and endurance cycles (> 105). The results will provide valuable ideas to overcome the challenge of endurance in the Fe-HfO2-based FeFET and contribute to developing other high-performance electron devices with Fe-HfO2 films grown on a dielectric SL.