Improved Step Coverage of Cu Seed Layers by Magnetic-Field-Assisted Ionized Sputtering

The relationship between the ion flux of self-ionized sputtering and the static magnetic field supplied by DC coils was investigated by ion current measurements. The ion flux was clarified in order to increase the substrate ion current. The additional magnetic field perpendicular to the substrate increases the substrate ion current and decreases the side electron current. The suppression of Cu ion diffusion increases the substrate ion current of self-ionized sputtering and the current distribution depends on the magnetic field configuration. A stronger magnetic field in the region of the wafer edge is necessary to increase the substrate ion current. This condition results in an increase in bottom step coverage and any asymmetry at the wafer edge is also corrected.