Development of biased directional sputtering (BDS) for barrier metal formation

This paper reports the biased directional sputtering (BDS), which is high d irectional sputtering using RF magnetron plasma and substrate bias, for for mation of barrier metals (Ti, TiN, Ta and TaN). The RF magnetron plasma, wh ich is denser than conventional DC magnetron plasma, ionizes sputtered meta l atoms efficiently, and the substrate bias accelerates the ionized metal a toms perpendicularly to the substrate surface. As a result, excellent step coverage can be obtained for high aspect ratio (AR) holes. The step coverag e of about 40% (AR = 6.0) for Ti and TIN, 40% (AR = 5.0) for Ta and 30% (AR = 5.0) for TaN are obtained. As regards the deposition shape in a hole, th ere is no difference in the shape between the hole in the center and that a t the edge on the wafer, and the shape of the deposition is symmetrical to the holes at both the positions. The deposition rates are 40 nm/min for Ti, 20 nm/min for TiN, 30 nm/min for Ta and 50 nm/min for TaN. Further, the re sistivity is less than 100 mu Ohm cm for Ti and TIN, and less than 300 mu O hm cm for Ta and TaN. (C) 2000 Elsevier Science Ltd. All rights reserved.