Surface Chemical Modification for Via-Hole Filling Using Tri-Isobutylaluminum Chemical Vapor Deposition

Tri-isobutylaluminum decomposition occurs preferentially on aluminum rather than silicon oxide surfaces. This preference might be exploited to fill via holes for multi-level integrated circuit metallizations. Initially a KrF excimer laser (248 nm) was used to sensitize aluminum pads in the base of the via holes. However, depending on the chemical treatment of the surface, it was discovered that laser enhanced activation was not required to obtain nucleation. At 240”C spontaneous aluminum growth can be made to occur exclusively in the via holes simply by utilizing appropriate cleaning methods. This technique was used successfully to fill via holes 1 μπι in diameter and 0.7 μπι deep with aluminum plugs. Selectivity is excellent, but chamber contamination can result in random nucleation. Technical problems still to be over come include grain growth morphology, 100 % via hole activation and better control of nucleation selectivity.