Characterization of Ferroelectric Al0.7Sc0.3N Thin Film on Pt and Mo Electrodes

Abstract

In the past decade, aluminum scandium nitride (AlScN) with a high Sc content has shown ferroelectric properties, which provides a new option for CMOS-process-compatible ferroelectric memory, sensors and actuators, as well as tunable devices. In this paper, the ferroelectric properties of Al0.7Sc0.3N grown on different metals were studied. The effect of metal and abnormal orientation grains (AOGs) on ferroelectric properties was observed. A coercive field of approximately 3 MV/cm and a large remanent polarization of more than 100 μC/cm2 were exhibited on the Pt surface. The Al0.7Sc0.3N thin film grown on the Mo metal surface exhibited a large leakage current. We analyzed the leakage current of Al0.7Sc0.3N during polarization with the polarization frequency, and found that the Al0.7Sc0.3N films grown on either Pt or Mo surfaces have large leakage currents at frequencies below 5 kHz. The leakage current decreases significantly as the frequency approaches 10 kHz. The positive up negative down (PUND) measurement was used to obtain the remanent polarization of the films, and it was found that the remanent polarization values were not the same in the positive and negative directions, indicating that the electrode material has an effect on the ferroelectric properties.

Nanoscale compositional segregation in epitaxial AlScN on Si (111)

“…3–6 Because electrical leakage is a major challenge in AlN-based ferroelectrics and piezoelectrics, many recent studies have highlighted methodologies to improve device stability by mitigating leakage currents and dielectric breakdown. 7–13 Some reports of abnormally oriented grains suggest that there are structural origins underlying problems with device performance. 14–16…”

“…[3][4][5][6] Because electrical leakage is a major challenge in AlN-based ferroelectrics and piezoelectrics, many recent studies have highlighted methodologies to improve device stability by mitigating leakage currents and dielectric breakdown. [7][8][9][10][11][12][13] Some reports of abnormally oriented grains suggest that there are structural origins underlying problems with device performance. [14][15][16] A significant fraction of ferroelectric/piezoelectric devices reported in the current literature are fabricated from columnar nanocrystals, making a systematic structure-based study difficult.…”

A Comparative Study of Pt/Al0.72Sc0.28N/Pt-Based Thin-Film Metal-Ferroelectric-Metal Capacitors on GaN and Si Substrates

“…However, ferroelectricity in Al x Sc 1– x N is not without limitations. One of the major issues is the high leakage current during switching. , With thickness downscaling, this issue becomes more severe, posing a significant obstacle to its usage in energy-efficient, ferroelectric-based electronics. In one of our recent works, we grew epitaxial Al x Sc 1– x N on n -doped GaN/Al 2 O 3 substrates .…”

Editorial for Special Issue “Piezoelectric Aluminium Scandium Nitride (AlScN) Thin Films: Material Development and Applications in Microdevices”

“…In the last section, six papers address the fabrication and performance of various AlScN-based devices [ 12 , 13 , 14 , 15 , 16 , 17 ]. It has been recognized quite early in the development of AlScN that the etching rate drops dramatically compared to pure AlN, and the existing etching approaches used for group-III nitrides must be revised, especially when vertical side-wall geometry has to be well controlled.…”

“…The authors were able to demonstrate vertical wall formation at this Sc concentration by exposing the specific planes of AlScN to KOH, which could benefit lamb wave resonators or similar released structures in the future. In a device, it is not only the functional layer that contributes to the overall performance, as shown in the study by Nie et al [ 13 ], where the ferroelectric properties of AlScN are investigated on different metals used for bottom electrodes. In samples with a Mo bottom electrode, a larger polarization loss was observed compared to those where Pt was used.…”