Aggressively scaled ultrathin undoped HfO2 gate dielectric (EOT<0.7 nm) with TaN gate electrode using engineered interface layer

The ultrathin HfO2 gate dielectric (EOT < 0.7 nm) has been achieved by using a novel "oxygen-scavenging effect" technique without incorporation of nitrogen or other "dopants" such as Al, Ti, or La. Interfacial oxidation growth was suppressed by Hf scavenging layer on HfO2 gate dielectric with appropriate annealing, leading to thinner EOT. As the scavenging layer thickness increases, EOT becomes thinner. This scavenging technique produced a EOT of 7.1 angstrom, the thinnest EOT value reported to date for "undoped" HfO2 with acceptable leakage current, while EOT of 12.5 angstrom was obtained for the control HfO2 film with the same physical thickness after 450 1 C anneal for 30 min at forming gas ambient. This reduced EOT is attributed to "scavenging effect" that Hf metal layer consumes oxygen during anneal and suppresses interfacial reaction effectively, making thinner interface layer. Using this fabrication approach, EOT of similar to 0.9 nm after conventional self-aligned MOSFETs process was successfully obtained.