Interface control by modified sputtering on Pt/HfO2/Si system

Hafnium oxide (HfO2) thin films were deposited by two different sputtering methods. In one case, hafnium (Hf) metal layer was pre-deposited before reactive sputtering process (method A), with the object of suppressing growth of the interfacial layer. Another one is conventional reactive sputtering, using DC magnetron in Ar+O2 ambient (method B). Films made by method A showed thinner interlayer as well as good leakage current behavior, demonstrating that Hf pre-deposited layer can protect from incorporation of the oxidizing species. With high-temperature annealing, interfacial layer increases considerably, showing composition changes from silicate to SiO2 (method A). In contrast, films by method B displayed little change in interlayer thickness since there exists previously thick SiOx bottom layer formed by O2 stabilizing before reactive sputtering. Equivalent oxide thickness (EOT) of as-deposited and annealed HfO2 films by method A is calculated to be ∼20 and ∼30 Å, respectively, with allowable level of leakage current density.