| abstract |
A copper metallization structure and its method of formation in which a layern(100) of a copper alloy, such as Cu-Mg or Cu-Al is deposited over a silicon oxidenbased dielectric layer (64) and a substantially pure copper layer (102) is depositednover the copper alloy layer (100). The copper alloy layer (100) serves as a seed ornwetting layer for subsequent filling of via holes (66) and trenches with substantiallynpure copper and also provides barriers at the interfaces with the underlying dielectricnand the overlying pure copper. The copper alloy may be deposited cold in a sputternprocess, but, during the deposition of the pure copper layer (102) or afterwards in anseparate annealing step, the temperature is raised sufficiently high to cause thenalloying element of the copper alloy to migrate to the dielectric layer (64).nAlternatively, the copper alloy may be deposited with the wafer held at an elevatedntemperature. The alloying element that has migrated to the oxygen-rich surfacesnoxidizes to form thin stable layers (70), for example of magnesium or aluminumnoxide, that act as barriers there against diffusion of copper into and through thendielectric layer (64). The inner barrier also promotes adhesion of the alloy layer to thendielectric layer (64), thereby forming a superior wetting and seed layer for subsequentncopper full-fill techniques. Filling of the alloy-lined feature can be accomplishednusing PVD, CVD, or electro/ electroless plating. |