Ferroelectric Al1-xScxN Opposite State Retention Model Based on Switching Dynamics

Wurtzite-structured ferroelectrics, such as aluminum scandium nitride (Al<inf>1-x</inf>Sc<inf>x</inf>N), are among the most promising candidates for implementing innovative nonvolatile memory concepts into commercial technologies. However, the opposite state (OS) retention limits the long-term retention performances. Since verifying the retention requirement directly up to 10 years, as typically targeted by commercial technologies, is timely unfeasible, developing a model to predict the 10-year OS retention performances of wurtzite-structured ferroelectrics is of the utmost importance for validating their reliable long-term operation. This work demonstrates the imprint as the primary factor in determining the Al<inf>1-x</inf>Sc<inf>x</inf>N OS retention performances. A model to predict the 10-year OS retention performances of Al<inf>1-x</inf>Sc<inf>x</inf>N is developed by directly correlating the coercive field (E<inf>c</inf>) increase with the slowing down of the switching dynamics through the relationship between the characteristic switching time and applied electric field magnitude to E<inf>c</inf> ratio (E/E<inf>c</inf>). The model is verified with OS retention measurements performed on Al<inf>0.85</inf>Sc<inf>0.15</inf>N capacitors after baking for up to 2 weeks at 150 °C. The E/E<inf>c</inf> that guarantees reliable 10-year OS retention performances is extrapolated for pulse widths down to the nanosecond range. Finally, electric field switching cycling is proven as a viable strategy for recovering from the imprint that degrades OS retention performances.