Journal of the electrochemical society vol:153 issue:4 pages:F60-F67
To facilitate selective removal of the gate dielectric toward the gate electrode, wet etch characteristics of HfSiOx and HfSiOx(N) in acidified HF solutions were determined as a function of several process parameters. Etch behavior of Hf-silicates was found to be little influenced by the various chemical vapor deposition processes. The top part (0-2 nm) of thick Hf-silicate layers etched similar to as-deposited thin layers (< 2 nm), while the bulk part etched significantly more slowly. However, etch rates were strongly dependent on composition (lower for Hf-rich silicates). Also, the removal rate of HfSiOx(N) was mainly dependant on the amount of incorporated nitrogen and crystallization temperature. Thermally nitrided layers were easier to remove compared to plasma-nitrided layers. Postnitridation anneals at high temperature in nitrogen environment decreased the etch rate. After removal, Hf concentrations below 1x10(11) atoms/cm(2) for most of the HfSiOx(N) layers under study were observed after a short (typically a few seconds) etch process in a single-wafer spin-cleaning tool.