Suppression of interfacial reaction for HfO2 on silicon by pre-CF4 plasma treatment

In this letter, the effects of pre-$\mathrm{C}{\mathrm{F}}_4$ plasma treatment on Si for sputtered $\mathrm{Hf}{\mathrm{O}}_2$ gate dielectrics are investigated. The significant fluorine was incorporated at the $\mathrm{Hf}{\mathrm{O}}_2∕\mathrm{Si}$ substrate interface for a sample with the $\mathrm{C}{\mathrm{F}}_4$ plasma pretreatment. The Hf silicide was suppressed and Hf–F bonding was observed for the $\mathrm{C}{\mathrm{F}}_4$ plasma pretreated sample. Compared with the as-deposited sample, the effective oxide thickness was much reduced for the pre-$\mathrm{C}{\mathrm{F}}_4$ plasma treated sample due to the elimination of the interfacial layer between $\mathrm{Hf}{\mathrm{O}}_2$ and Si substrate. These improved characteristics of the $\mathrm{Hf}{\mathrm{O}}_2$ gate dielectrics can be explained in terms of the fluorine atoms blocking oxygen diffusion through the $\mathrm{Hf}{\mathrm{O}}_2$ film into the Si substrate.