Dry Etching of Mo based layers and its interdependence with a poly-Si/MoOxNy/TiN/HfO2 gate stack

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/MoOx and TiN/MoOxNy layers used in poly-silicon metal gate stacks. We found that for these Mo based layers, the dry etching using any Cl-2/O-2 ratio provoked a severe isotropic etching. HBr gas was used as a key component for controlling side-walls passivation. The MoOx and MoOxNy 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/MoOx and TiN/MoOxNy). 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. (C) 2012 Elsevier B.V. All rights reserved.