Improvement in electrical properties and thermal stability of low-temperature-processed Hf-Al-O gate dielectrics

In this letter, we report on the low temperature (∼350 °C) growth of Hf-Al-O dielectric films with improved thermal stability and electrical characteristics for gate dielectric applications. A higher capacitance and improved interfacial properties were observed in the films deposited with N H3 ambient followed by ultraviolet radiation assisted oxidation annealing. The films containing 10.6 at. % Al were found to remain amorphous after a 900 °C furnace anneal for 1 min in flowing nitrogen. The flat-band voltage was stabilized by nitrogen incorporation with negligible shift. An equivalent oxide thickness of 19 Å and a dielectric constant of 20.4 were obtained in the best samples processed in N H3 and ultraviolet radiation ambient.