Selective dry etching of La2O3/Si stacked film

Summary form given only: A stacked film structure of lanthanum oxide and silicon (La₂O₃/Si) is considered to be used in MOSFETs in the Nano-CMOS era since La₂O₃ is a promising high-k gate insulator. In the substrate contact formation process, La₂O₃ should be removed selectively against Si substrate. In order to examine the possibility of the selective dry etching of La₂O₃/Si stacked film, dry etching characteristics of La₂O₃ and Si were investigated. As a result, it was found that pure Ar sputtering as well as an addition of Cl₂, BCl₃ or CF₄ to Ar caused higher etching rate of Si than that of La₂O₃, which led to a low etching selectivity. In Ar plasma in a chamber with B contaminations, however, Si was not etched while La₂O₃ was etched with the etching rate about 2 nm/min. X-ray photoelectron spectroscopy revealed that B existed only on the etched Si surface, which was considered effective for preventing Si from being etched by Ar sputtering. As a conclusion, noble gas plasma, such as Ar plasma, with small amount of B fluxes to the etching surface enables the La₂O₃/Si selective etching.