Copper metallization of submicron trenches with pulsed vacuum arc

The fast development of microelectronics means for metallization 1) smaller width of trenches and vias, 2) higher aspect ratio, 3) transition to copper. Conventional PVD methods and even adapted versions (e.g. directed sputtering) have large problems to meet the future demands, especially to realize complete filling of the deeper structures. A very promising alternative is represented by special versions of vacuum arc deposition. The plasma beam generated in the vacuum arc discharge is distinguished by its complete ionization and by its high kinetic energy. Up to now this technique seems to be not acceptable for microelectronic technologies due to the inherent problem of droplet emission. By the development of the pulsed High Current Arc (HCA) the melt splashing effect is markedly reduced. For completely droplet-free deposition an additional magnetic filtering was developed. Due to its specially designed high efficiency and due to the high rate of the HCA it allows the integration in the time cycle of a cluster tool. Complete copper filling of 1 μm trenches with aspect ratios up to 3 has been achieved. Further optimization includes the effects of enhanced subatrate temperature and of scattering on a gas atmosphere. Based on the thorough analysis of the dependence of the growth rate on orientation and on the geometrical conditions in the neighborhood a theoretical model has been developed. According to this concept, the deposition must be considered as a dynamic process including sputtering and redeposition on the highly activated surface.