Electroless NiWP and NiReP films were investigated with the aim of application to barrier and capping layers in interconnect technology. These alloys containing a refractory metal with a high melting point were expected to have the ability to avoid diffusion of Cu into the interlevel dielectric. The composition and resistivity of these films were investigated first in order to know the relation between the composition and its thermal stability. The thermal stability was investigated by measuring the sheet resistance and the cross-sectional observation with field emission scanning electron microscope. Additionally, an electroless Ni alloy deposition on the SiO 2 layer without a sputtered seed layer was also examined by utilizing a self-assembled monolayer ͑SAM͒ as an adhesion and catalytic layer. Since an alkaline solution damaged the SiO 2 surface, a two-step process, which consists of a nucleation step performed in an acid electroless deposition bath and a barrier layer formation step carried out in an alkaline bath, is employed in order to fabricate a consistently uniform barrier film on the SAM/SiO 2 surface. It was found that the NiReP films formed on SAM/SiO 2 surfaces were stable up to 400°C, and are feasible for the barrier layer for the Cu interconnect technology.

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Copper (Cu) damascene interconnects with a cobalt tungsten phosphorus (CoWP) capping layer were developed using an alkaline-metal-free electroless plating process .without palladium (Pd) catalyst activation. The wafer contamination level after processing is consistent with requirements for present LSI fabrication lines. Within wafer CoWP deposition uniformity is high and interconnects wire resistance increases by less than 5% after deposition. Electromigration (EM) testing shows no failures after two thousand hours and stress induced voiding (SIV) testing shows no failures after three thousand hours. This EM result is a 2 order of magnitude improvement over a non CoWP process.