ALUMINUM METALLIZATION USING A COMBINATION OF CHEMICAL-VAPOR-DEPOSITION AND SPUTTERING

An aluminum metallization process that combines blanket chemical vapor deposition and sputtering was developed for use in fabrication of fut ure ultralarge scale integration interconnections. Blanket chemical va por deposition of aluminum using dimethylaluminum hydride on titanium nitride, which provides superior step coverage and a smooth surface mo rphology for films of less than approximately 0.15 mu m thickness, was only used for hole-filling. Subsequent aluminum alloy sputtering, whi ch has a high deposition rate and provides smooth surface films, was u sed for the thickening of the aluminum films. This combination process draws on the respective advantages of both chemical vapor deposition 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 fabr icated by the combination process was slightly lower than that obtaine d in the conventional tungsten plug process due to low film resistivit y of chemically vapor deposited aluminum. The contact resistivity for contacts to p- and n-type Si were 1.0 x 10(-7) and 2.9 x 10(-8) Omega cm(2). respectively. Via hole resistance for 0.45 mu m diameter holes was less than 1 Omega, which corresponds to a contact resistivity of l ess than 1.6 x 10(-9) Omega cm(2) between chemically vapor deposited a luminum and the underlayer titanium nitride.