Ferroelectric Switching in Sub-20 nm Aluminum Scandium Nitride Thin Films

Ferroelectric switching was studied in 20 nm thick Al0.68Sc0.32N and Al0.64Sc0.36N films (with 4 nm surface oxides) on platinized silicon wafers by multiple electrical characterization methods. Positive up negative down (PUND) measurements were conducted using 100 \mu s monopolar triangular waveform excitation. At room temperature, Al0.68Sc0.32N exhibited an apparent remanent polarization, P r}} = {140}\,\,\mu C /cm2 and a coercive field, E c}} = {6.5 MV/cm, while film leakage prevented quantitative measurement of the Al0.64Sc0.36N ferroelectric properties. Remanent polarizations of 75~\mu C /cm2 for Al0.68Sc0.32N and 25\mu C /cm2for Al0.64Sc0.36N were measured at 120 K. Partial ferroelectric switching was confirmed at room temperature for both materials via the measured transverse piezoelectric coefficients (e31, f) of -1.3 C/m2 (down-switching) and -0.3 C/m2 (up-switching) for Al0.68Sc0.32N, and -0.9 C/m2 (down-switching) and -0.7 C/m2 (up-switching) for Al0.64Sc0.36N.