Titanium sputter deposition at low pressures and long throw distances

Sputter deposition of titanium into trench and via topography has been studied under conditions of pressure as low as 0.3 mTorr (0.04 Pa) for long (30 cm) and short (9 cm) throw distances. Film resistivity and deposition rates at both distances have been measured for pressures from 0.3 mTorr up to 5 mTorr (0.67 Pa). Pinhole experiments have been used to examine the evolution of the angular distribution of sputtered flux as a function of pressure and distance. The experimental results show that by increasing the throw distance and reducing pressure, the bottom coverage in high aspect ratio topographical features may be increased to almost 90% but thickness nonuniformity under these conditions remains a significant problem due to the size of the target. We have tested for the presence of resputtering in the highly energetic, low collision regime which arises at low pressure and no resputtered material has been detected.