Aggressively scaled ultra thin undoped HfO/sub 2/ gate dielectric (EOT<0.7 nm) with TaN gate electrode using engineered interface layer

Abstract

The ultrathin HfO/sub 2/ 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 HfO/sub 2/ 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 /spl Aring/, the thinnest EOT value reported to date for "undoped" HfO/sub 2/ with acceptable leakage current, while EOT of 12.5 /spl Aring/ was obtained for the control HfO/sub 2/ film with the same physical thickness after 450/spl deg/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 /spl sim/ 0.9 nm after conventional self-aligned MOSFETs process was successfully obtained.