Improved electrical performance of ultra-thin BexMg1−xO films using super-cycle atomic layer deposition†

This research explores the high-k dielectric behavior of ultra-thin BeMgO (BMO) films (≪5 nm) using the super-cycle atomic layer deposition (ALD) technique. The fabricated metal–insulator–metal devices, utilizing sputtered TiN as both bottom and top electrodes, demonstrate low leakage current and high capacitance characteristics with a minimum equivalent oxide thickness of 1.30 nm. The dielectric constants of the films are significantly higher than those of pure MgO or BeO films, reaching a maximum value of 14.2 at a film composition of Be_0.29Mg_0.71O, indicating the realization of the cubic rocksalt configuration of Be–O bonds. The rocksalt phase remains dominant even in Be-rich BMO films due to the structural coherence with the TiN electrodes, revealing the intricate interplay between composition and interface engineering. BMO films showed exceptional electrical stability even at a film thickness of 2.5 nm, demonstrating their strong dielectric strength. The trap-assisted tunneling mechanism governed the leakage current at this thickness. Such attributes make BMO films highly appealing in dynamic random-access memory capacitors, where the industry's relentless drive toward miniaturization necessitates ultra-thin dielectric films with uncompromising performance.