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Abstract

A method of fabricating a semiconductor device having contaminant-reduced calcium-copper (Ca--Cu) alloy surfaces formed on Cu interconnects by cost-effectively removing the contaminant layer and a device thereby formed. Contaminant removal from a Cu--Ca--X surface, where contaminant X=C, S, or O, is achieved by sputtering the Cu--Ca--X surface in an argon (Ar) atmosphere between the steps of (a) immersing the Cu interconnect surface into an electroless plating solution comprising Cu salts, Ca salts, their complexing agents, a reducing agent, a pH adjuster, and at least one surfactant for facilitating Ca-doping of the Cu interconnect material; and (b) annealing of the Ca--Cu alloy surface onto the underlying Cu interconnect material to form a Ca--Cu/Cu interconnect structure, whereby the sputtering step, under Ar, selectively and effectively removes contaminants from the Cu--Ca--X layer containing higher concentrations of C, S, or O, thereby minimizing the post-annealed contaminant level, and thereby producing a uniform Ca--Cu alloy surface (i.e., Cu-rich with 0.2-5% Ca) on the Cu interconnect material for maximizing Ca--Cu/Cu interconnect structure reliability, electromigration resistance, and corrosion prevention. The annealing step primarily removes O and secondarily removes C and S, especially when performed under vacuum, an inert gas, or a reducing ambient such as ammonia (NH.sub.3) plasma. Thus, the resultant device then comprises a distinctive contaminant-reduced Ca--Cu/Cu interconnect structure.

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First Claim