Extreme Scaled Gate Dielectrics By Using ALD HfO 2 /SrTiO 3 Composite Structures

A sub 1-nm equivalent oxide thickness (EOT) gate stack with conduction band edge effective work function is demonstrated with an ALD deposited HfO2/SrTiO3 based composite material. An EOT reduction of 0.2 nm as compared to the HfO2 reference is obtained after applying a high thermal budget in a gate first transistor flow. A comparison with ALD HfO2/La2O3 and HfO2/MgO composite stacks is made. Results suggest that the EOT reduction and threshold voltage shift (Vt) are determined by the Sr, La or Mg diffusion inside the dielectric stack and into the interface oxide after a thermal treatment. The onset of this diffusion is temperature dependent and differs from stack to stack.