The Effect of Thermal Annealing on Cobalt Film Properties and Grain Structure

The grain structure of electrodeposited Cobalt is important to device electrical and reliability performance. This paper describes thermal annealing studies performed on electroplated blanket and pattern Cobalt wafers. A systematic study of Co film properties and effect of various anneal parameters such as temperature, time, hydrogen pressure and thermal cycling was completed. Co film resistivity, purity, grain structure, phase composition and orientation as well as in-feature grain size have been characterized by various analytical methods such as XRD, STEM, SIMS and EBSD. It was observed that electroplated cobalt films with resistivity approaching bulk Cobalt value can be obtained by annealing in the temperature range of 300°C - 350°C which is favorable for hcp Co phase formation.