Dry Etching of Mo based layers and its interdependence with a poly-Si/MoO_xN_y/TiN/HfO_2 gate stack

摘要

Further device scaling below the 65 nm node required the introduction of metal gates/high-k layers. This paper discusses the etching approaches for patterning TiN/Mo, TiN/MoO_x and TiN/MoO_xN_y layers used in poly-silicon metal gate stacks. We found that for these Mo based layers, the dry etching using any C1_2/O_2 ratio provoked a severe isotropic etching. HBr gas was used as a key component for controlling side-walls passivation. The MoO_x and MoO_xN_y layers were more prone to lateral attack compared to Mo due to the intrinsic stoichiometric oxygen. A good selectivity towards the substrate was obtained using high O_2 flows in Cl_2/O_2/HBr mixtures. Etching of the TiN layer was carried out with Ar/Cl_2. This process was tuned by adding HBr depending on the metal gate stack, which suggests that TiN etching is highly influenced by the Mo layer nature (TiN/Mo, TiN/MoO_x and TiN/MoO_xN_y). We have also compared the complete gate stack pattering characteristic when an oxide or an amorphous carbon hard mask has been used for pattern definition.