Polarity Reversal of Dipole at the SiO2/HZO Interface in Ferroelectric Field-Effect Transistors by Oxygen Scavenging of TiN

Abstract Doped HfO2-based ferroelectric field-effect transistors (FeFETs) have attracted considerable attention for their potential in nonvolatile memory applications. Research on the dipole at the SiO2/HfO2-based ferroelectric interface is scarce. This study finds that the polarity of dipole at SiO2/Hf0.5Zr0.5O2 (HZO) is reversed after TiN deposition on HZO. The mechanism of polarity reversal is investigated by X-ray photoelectron spectroscopy (XPS). The results show that TiN induces oxygen scavenging in HZO due to the Zr−O bond breaking and generates more oxygen vacancies near the HZO/TiN interface. More oxygen vacancies change the relative position of charge neutrality level (CNL) between SiO2 and HZO, leading to the polarity reversal of dipole at the SiO2/HZO interface. O2 PDA is helpful to suppress the oxygen scavenging behavior after TiN deposition and modulate the dipole distribution. This work will be valuable to understand the distribution of dipole at the interlayer/FE interface and beneficial to improve the reliability of FeFET devices through band engineering employing dipole modulation.