Low Voltage Operation of Ferroelectric AlScN Films by Oxygen Profiling

A method to reduce the high coercive field (Ec) of ferroelectric (FE) Al0.7Sc0.3N films was proposed. By proper oxygen incorporation to form Al0.7Sc0.3O0.2N0.8, Ec reduction from 3.8 to 2.8 MV/cm was achieved while maintaining a high remnant polarization (Pr) of over 90 µC/cm2. The Ec reduction is presumably caused by the O and Al atom complex vacancies; different from the Sc-atom induced distortion to decrease the ratio of wurtzite lattice constant (c/a). A dielectric constant increase from 17 to 30 supports the Ec reduction. By designing the oxygen depth profile in the film, FE property was obtained with a thickness down to 7 nm. Even the Ec increase with thinner thickness is still presented, a ferroelectric switching was confirmed at a voltage below 5 V.