Cobalt polishing slurries for 10 nm and beyond

The semiconductor industry is continually driven to improve chip performance by further miniaturization of devices by process, materials, and integration innovations. Earlier materials innovations included the introduction of copper (Cu), replacing aluminum as the conductive material in the interconnect structure, and the use of tantalum (Ta) (adhesion)/tantalum nitride (TaN) (barrier) to separate the Cu conductive material from the non-conductive/insulator dielectric material. However, with progressive shrinkage in chip real estate, at the most advanced nodes, the current Cu/TaN/Ta materials are in need of new materials innovation. This is because with smaller dimensions and advanced manufacturing nodes, resistivity is getting exponentially worse, and conformal deposition in thin line space is becoming impossible for the Cu/TaN/Ta stack. Cobalt (Co) has emerged as a leading candidate for both the barrier layer (TaN/Ta) as well as the conductive layer (Cu) replacement [1]. Co has some unique properties such as conformal deposition (especially in high aspect ratio areas), sticky properties, inexpensive adhesion techniques, high resistivity to act as a barrier (Ta/TaN replacement), and large scale, inexpensive commercial availability. However, there are some major drawbacks of Co; the most significant being corrosion. In the CMP of Co, one of the major problems that the industry is facing is the corrosion and defectivity of Co films post-CMP. Although Co is mechanically harder than Cu (Mohs Hardness of 5 vs. 3), it is chemically much more fragile than Cu and thus, less noble than Cu. So, Co is much more susceptible to corrosion and oxidation. Corrosion in Co CVD/PVD films can be general, pitting and/or galvanic corrosion. In order to successfully commercialize Co as the material of choice for next generation semiconductor manufacturing, the CMP community has to overcome Co corrosion problems. Fujifilm Planar Solutions (FFPS) has a very active Co CMP slurry program. H- rein, we will be primarily presenting our Co bulk slurry platform, with focus on platform design, Material Removal Rates, dishing improvement, corrosion improvement, defectivity reduction, and electrochemical studies (Tafel, corrosion current/potential, etc.). Some of the results on our Co slurry are presented in Fig. 1.