Interface control of advanced electronic devices -High-k/metal gate system and magnetic tunneling junction

Key issues on interface control of the constituent materials are taken up and reviewed with respect to scaled logic and memory. For logic devices with high-k/metal gate, amount of oxygen vacancy in the high-k dielectric determines the effective workfunction by modulating the workfunction derived from the high-k/metal gate materials. Concerning the EOT control of HfO₂, by controlling the oxidation time of pre-deposited metal-Hf, precise thickness control of the interfacial layer including no interface layer with excellent uniformity is achieved. In the meantime, for a magnetic tunnel junction (MTJ) for spin-transfer-torque switching, a redox reaction is found to occur at the surface of Ta/CoFeB/MgO/CoFeB where the oxidized cobalt and iron are reduced by the boron atoms that diffuse toward the top CoFeB surface. It is imperative to protect the MTJ surface from oxidation/ hydroxylation to obtain an accurate tunnel current.