Aluminum metallization using a combination of chemical vapor deposition and sputtering

An aluminum metallization process that combines blanket chemical vapor deposition (CVD) and sputtering was developed for use in the fabrication of future ultralarge scale integration interconnections. Silicon wafers, bearing sputtered titanium nitride layers, were the substrates. Blanket CVD of aluminum using dimethylaluminum hydride on titanium nitride, which provides superior step coverage and a smooth surface morphology for films of less than approx0.15 mu m thickness, was only used for hole-filling. Subsequent aluminum alloy sputtering, which has a high deposition rate and provides smooth surface films was used for the thickening of the aluminum films. This combined process draws on the respective advantages of both CVD and sputtering, which mutually compensate for each other's drawbacks. As a result, via holes with a diameter of 0.3 mu m and an aspect ratio of 2.7 were successfully filled. The resistance of contact holes fabricated by the combined process was slightly lower than that obtained in the conventional tungsten plug process due to low film resistivity of CVD aluminum. The contact resistivity for contacts to p- and n-type silicon were 1.0x10 exp -7 and 2.9x10 exp -8 Omega cm exp 2 , respectively. Via hole resistance for 0.45 mu m diameter holes was less than 1 Omega , which corresponds to a contact resistivity of less than 1.6x10 exp -9 Omega cm exp 2 between CVD aluminum and the underlayer titanium nitride.