Cobalt filling of interconnects in microelectronics

A process for electroplating a cobalt deposit onto a semiconductor base structure comprising submicron-sized electrical interconnect features, wherein the submicron-sized electrical interconnect features comprise a plurality of cavities in the semiconductor base structure, each cavity of said plurality having a bottom, sidewall, and top opening, wherein an entry dimension of the plurality of cavities is not greater than 20 nm, the process comprising the steps of:

• contacting a metalizing substrate within said submicron-sized electrical interconnect features with an electrodeposition composition comprising:
• a source of cobalt ions;
• an acetylenic suppressor compound;
• a buffering agent;
• and
• water;
• said electrodeposition composition being substantially free of any divalent sulfur compounds;
• and free of any functional concentration of reducing agents effective to reduce cobaltous ions (Co2+) to metallic cobalt (Co0);
• and
• supplying electrical current to the electrodeposition composition to deposit cobalt onto the semiconductor base structure and fill the submicron-sized electrical interconnect features with cobalt,
• wherein said cobalt deposit contains less than 300 ppm sulfur,
• wherein said electrodeposition composition is substantially free of any further additive that would function as an accelerator;
• and
• wherein the cobalt deposit is substantially free of voids and other defects.