Effects of rapid thermal annealing after plasma H2 pretreatment of the copper seed layer surface on copper electroplating

In ULSI fabrication. copper is widely accepted as a new interconnect material to replace aluminum and its alloys due to its low resistivity and high electromigration resistance. Cu seed layers for copper electroplating were deposited by magnetron sputtering on silicon wafers using TaN as diffusion barriers between the seed layer and silicon. Effects of plasma H-2 pretreatment and also the combined effects of plasma H-2 pretreatment and rapid thermal annealing of the Cu seed layers have been investigated on the physical properties including the resistivity, the grain size and the surface roughness of the electroplated copper films. The best physical properties were obtained for the electroplated copper film on the TaN film the surface of which was given the plasma H-2 treatment at the rf-power of 100 W for 10 min followed by rapid thermal annealing at 350 degreesC for 30 s. The mechanism of the cleaning process has also been discussed.