US Patent 7129162 Dual cap layer in damascene interconnection processes

Damascene methods for forming copper conductors (30, 130) are disclosed. According to the disclosed method, a dual cap layer (18, 20; 122, 124) is formed over an organosilicate glass insulating layer (16; 116, 120) prior to the etching of a via or trench toward an underlying conductor (12; 112). The dual cap layer includes a layer of silicon carbide (18; 124) and a layer of silicon nitride (20; 122). The silicon carbide layer (18; 124) and silicon nitride layer (20; 122) can be deposited in either order relative to one another. The silicon carbide layer (18; 124) maintains the critical dimension of the via or trench as it is etched through the insulating layer (16; 116, 120), while the silicon nitride layer (20; 122) inhibits the failure mechanism of resist poisoning. The method is applicable to single damascene processes, but may also be used in dual damascene copper processes.