Correlation between ferroelectricity and nitrogen incorporation of undoped hafnium dioxide thin films

Abstract

The ferroelectric characteristics of undoped hafnium oxide (HfO2) in titanium nitride (TiN)/HfO2/TiN stacks exhibited improved remanent polarization by controlling the nitrogen gas flow during TiN deposition in this work. Electrical measurements revealed that samples with a higher N-2/(Ar + N-2) ratio obtained a higher remanent polarization of approximately 10 mu C/cm(2) at 2.5 V but exhibited a larger leakage current and less reliability. Among all the samples, the sample with a N-2/(Ar + N-2) ratio of 33% exhibited a relatively high remanent polarization of 12 mu C/cm(2) and excellent endurance over 10(8) cycles. Through X-ray photoelectron spectroscopy (XPS) analysis, it was observed that increasing the N-2 gas flow during TiN electrode deposition contributed to excessive N-diffusion, leading to the creation of more oxygen vacancies and subsequently to device failure. Therefore, controlling the appropriate N-2 gas flow during TiN deposition is crucial to enhance the ferroelectric characteristics of undoped HfO2. The results of this study may be applicable to future work on nonvolatile memory applications.