Planarization of aluminum films by a technique with the combination of molecular beam deposition and annealing for ultralarge-scale integration metallization

Abstract

Planarization of aluminum films has been achieved by using the combination of molecular beam deposition (MBD) and annealing for ultralarge-scale integration metallization. The resulting via holes for multilevel interconnection in the metallization are found to be filled by a plug of aluminum. This MBD is an effective deposition method for producing a desired aluminum film; the aluminum is fully deposited on the sidewall and bottom of vias without an overhang occurring. This desired aluminum film is realized because the direction of incoming aluminum vapor is controlled. The direction control is performed with an angle definition and scattering prevention of the vapor. A mass transport of aluminum is created during this annealing procedure. This desired aluminum film is needed in order to perform the via filling and planarization because the mass transport is attributed to the surface tension forces generated by the three-dimensional geometry of the heated aluminum. The resulting condition includes an undesired void in via hole if the aluminum is not fully deposited on the sidewall and bottom of vias. This technique has been shown to allow excellent via filling with the annealing at low temperature (300 °C), and is applicable to filling submicrometer-diameter vias having a diameter of 0.58 μm with a 1.1-μm depth (aspect ratio ∼1.9). The resulting surface of aluminum films is planarized.