Wet chemical etching studies of Zr and Hf-silicate gate dielectrics

Abstract

The etching properties of alternate gate dielectric candidates Hf and Zr silicate in hydrofluoric acid (HF) solutions are presented. As-deposited Hf silicate films were found to be more difficult to etch when compared with as-deposited Zr silicate films. After annealing, both Hf and Zr silicate are harder to etch than as-deposited films. Annealed Zr silicate films were the most difficult to remove in either concentrated, or diluted HF solutions. Film densification, along with crystallization of the silicate films near the Si interface are thought to be responsible for the etch rate change in these silicate systems. Alternate processes to remove remnant metal from the silicon surface after gate dielectric removal are also discussed. After annealing and dielectric film removal, remnant Zr and Hf concentrations near the Si surface of ${\text{∼10}}^{19}/{\mathrm{cm}}^{\mathrm{3}}$ and ${\text{∼10}}^{16}/{\mathrm{cm}}^{\mathrm{3}},$ respectively, were observed.