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

Ferroelectric switching was studied in 20 nm thick Al
_0.68
Sc
_0.32
N and Al
_0.64
Sc
_0.36
N 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 μs monopolar triangular waveform excitation. At room temperature, Al
_0.68
Sc
_0.32
N exhibited an apparent remanent polarization, P
_r
= 140 μC/cm
²
and a coercive field, E
_c
= 6.5 MV/cm, while film leakage prevented quantitative measurement of the Al
_0.64
Sc
_0.36
N ferroelectric properties. Remanent polarizations of 75 μC/cm
²
for Al
_0.68
Sc
_0.32
N and 25μC/cm
²
for Al
_0.64
Sc
_0.36
N were measured at 120 K. Partial ferroelectric switching was confirmed at room temperature for both materials via the measured transverse piezoelectric coefficients (e
_31,
f
) of -1.3 C/m
²
(down-switching) and -0.3 C/m
²
(up-switching) for Al
_0.68
Sc
_0.32
N, and -0.9 C/m
²
(down-switching) and -0.7 C/m
²
(up-switching) for Al
_0.64
Sc
_0.36
N.