Ferroelectric behavior of sputter deposited Al0.72Sc0.28N approaching 5 nm thickness

Ferroelectric Al1-xScxN has raised much interest in recent years due to its unique ferroelectric properties and complementary metal oxide semiconductor back-end-of-line compatible processing temperatures. Potential applications in embedded nonvolatile memory, however, require ferroelectric materials to switch at relatively low voltages. One approach to achieving a lower switching voltage is to significantly reduce the Al1-xScxN thickness. In this work, ferroelectric behavior in 5-27 nm films of sputter deposited Al0.72Sc0.28N has been studied. We find that the 10 kHz normalized coercive field increases from 4.4 to 7.3 MV/cm when reducing the film thickness from 27.1 to 5.4 nm, while over the same thickness range, the characteristic breakdown field of a 12.5 mu m radius capacitor increases from 8.3 to 12.1 MV/cm. The 5.4nm film demonstrates ferroelectric switching at 5.5V when excited with a 500 ns pulse and a switching speed of 60 ns.