High stability of the ferroelectricity against hydrogen gas in (Al,Sc)N thin films

The changes in the crystal structure and ferroelectric properties of (Al0.8Sc0.2)N films sandwiched between Pt and TiN electrodes were investigated by subjecting the films to post-heat-treatment at various temperatures up to 600 °C in both H2 and Ar gases. The remanent polarization underwent slight change, whereas the coercive field strengthened by approximately 9% as a result of the post-heat-treatment up to 600 °C irrespective of the atmosphere and electrode material. This change is much smaller than that reported for ferroelectric (Hf,Zr)O2 films as well as for Pb(Zr,Ti)O3 and SrBi2Ta2O9 films for a wide temperature range from 400 to 600 °C and is almost independent of the Pt and TiN electrodes. The high stability of (Al,Sc)N films with both Pt and TiN electrodes under H2 atmosphere is highly promising to stabilize the properties through the device fabrication process.