STRESS-RELAXATION IN TUNGSTEN FILMS BY ION IRRADIATION

Tungsten films, grown by plasma-enhanced chemical vapor deposition for very large scale integration interconnect applications, suffer from a high internal tensile stress that leads to contact failure. We show w ith wafer curvature measurements that the stress can be relaxed via vi scous flow at room temperature by irradiating the films with energetic ions after deposition. Transmission electron microscopy does not indi cate significant structural changes in the W films during irradiation. We varied the irradiation conditions (from 140 keV B ions to 400 keV P ions) and find that the flow rate scales with the nuclear stopping p ower. Similarities and differences with beam-induced mixing and diffus ion are discussed. (C) 1997 American Institute of Physics.