Methods for etching tungsten stack structures

The invention encompasses methods for etching and/or over-etching tungsten stack structures, especially tungsten-polysilicon stack structures. The etching methods of the invention preferably employ a Cl2/NF3 etchant, optionally including O2 and/or helium. The over-etching methods of the invention preferably use a NF3/N2/O2 etchant. The methods of the invention enable effective etching of tungsten-polysilicon stacks where topographic variation is present across the substrate and/or where other tungsten stacks of different structure are also being etched.