Etching of high-$k$ and metal gate materials in high-density chlorine-containing plasmas

Plasma etching of high dielectric constant ($k)$ films and metal electrodes is indispensable for the fabrication of high-$k$ gate stacks. This paper presents the etching characteristics of high-$k$ materials of HfO$_{2}$ and metals of Pt and TaN using high-density chlorine-containing plasmas, along with the plasma and surface diagnostics concerned. Attention was focused on etch chemistries and plasma conditions to achieve a high etch selectivity of $>>$1 for HfO$_{2}$ over the underlying Si and SiO$_{2}$; regarding Pt and TaN, the emphasis was placed on the etch anisotropy and selectivity of metal electrodes over the underlying HfO$_{2}$ and overlying SiO$_{2} $. The etching of HfO$_{2}$ was performed in BCl$_{3}$ without rf biasing, giving an etch rate of about 5 nm/min with a high selectivity of $>$10 over Si and SiO$_{2}$. At lower pressures, the deposition of BCl$_{x}$ was found to occur on all the surfaces of interest; however, on HfO$_{2}$ surfaces, the deposition followed the etching during a few tens of seconds. The etching of Pt and TaN was performed with high and low rf biasing, respectively, giving a Pt etch rate of about several tens nm/min and a TaN etch rate of about 200 nm/min, with a high selectivity of $>$8 over HfO$_{2}$ and SiO$_ {2}$ in Ar/O$_{2}$ for Pt and in Ar/Cl$_{2}$ for TaN. The etched profiles were outwardly tapered for Pt, while the TaN profiles were found to be almost anisotropic.