Characteristics of high-k gate oxides prepared by oxidation of 1.4 nm multi-layered Hf/Al metal film

We investigated the physical and electrical properties of high-k gate oxide formed by oxidizing multi-layered Hf and Al metal films. We demonstrated that oxidation of multi-layered metal films results in two distinctive amorphous layers: That is, Hf- and Al-doped metal oxide films were formed on the top of silicate film. The thickness of silicate layer and therefore equivalent oxide thickness (EOT) value were dependent on the number of metal films. To reduce the EOT value, higher number of metal layers is desirable. In addition, annealing has to be done at 600 °C to obtain the minimum value of EOT. Hysteresis phenomenon usually observed in high-k oxide was not observed in this work.