Effect of Nitridation of Bottom Interlayer in FeFETs With the TiN/Al₂O₃/Hf_0.5Zr_0.5O₂/Bottom Interlayer/Si Substrate Structure

In this work, we investigate the effect of nitridation of the bottom interlayer in HfO2-based ferroelectric silicon channel field-effect transistors (HfO2 Si-FeFETs) with the TiN/top interlayer/ferroelectric/bottom interlayer/Si substrate (MIFIS) structure. We find that the SiON bottom interlayer induces a smaller memory window (MW) compared with the case of SiO2 as a bottom interlayer in the MIFIS structure. The origin is the reduced barrier height at the bottom interlayer induced by the positive charges in the SiON layer, which makes the charges injected from the metal gate cannot remain after erasing operation. However, the SiON bottom interface in the MIFIS structure shows higher endurance and stable retention than the SiO2 bottom interface. Thus, for the ferroelectric field-effect transistor (FeFET) gate stacks with a top interlayer (MIFIS structure), the SiO2 is more suitable than the SiON as a bottom interlayer to realize larger MW, while the SiON bottom interlayer can improve retention and endurance at the expense of MW.