TiN buffer-assisted low-temperature epitaxy of 4-inch AlScN films

Abstract

Abstract Wurtzite AlScN films have emerged as promising ferroelectric layers for next-generation memory and piezoelectric devices due to their high remanent polarization, excellent thermal stability (up to 1 100 °C), scalability to nanometer thickness, and back-end-of-line complementary metal–oxide–semiconductor compatibility. Although numerous efforts have been devoted to synthesizing AlScN epitaxial films, wafer-scale epitaxy (i.e., >2 inches) of AlScN ferroelectric films at very low substrate temperatures (i.e., <200 °C) has still not been achieved. Here, 4-inch AlScN epitaxial films were successfully deposited on bare and TiN-buffered α-Al 2 O 3 (0001) substrates using a homemade sputtering epitaxy system. The AlScN films with optimal crystalline quality exhibit a full width at half maximum (FWHM) of X-ray rocking curves as small as 0.02°, much smaller than the values reported in the literature (>0.1°). These AlScN films have high uniformity across the entire 4-inch wafer. More interestingly, the TiN buffer layer can facilitate low-temperature (100 °C) epitaxial growth of AlScN films due to a reduced lattice mismatch, achieving the lowest epitaxy temperature reported thus far. Our work establishes a scalable and low-thermal-budget pathway for synthesizing high-quality AlScN epitaxial films, which can significantly advance the development of AlScN-based electronic devices.