Interconnects on integrated circuits improved by excimer laser planarization for multilevel metallization

The use of excimer-laser planarization to improve interconnection on integrated circuits is described, and the effect of a thin Cu overcoating at the planarization step is considered. In the present experiment, the via-hole filling was achieved by melting an Al film with a single optical pulse (15 ns, approximately 5- approximately 20 J/cm/sup 2/) from an ArF excimer laser. This technique has been shown to realize excellent via filling without damaging the lower levels of interconnect, and is applicable to filling a via having a diameter of 0.7- mu m with approximately 1.0- mu m depth (aspect ratio approximately 1.4). The resulting surface was found to be planarized. The use of a thin Cu overcoating greatly enhances the Al planarization process by increasing the initial absorbance of the laser beam in the metal film, because the reflectivity of Cu ( approximately 20%) is lower than that of Al (>90%) for the ArF excimer laser beam.<>