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.