Significant enhancement in electromigration resistance and texture of aluminum films using an ultrathin titanium underlayer

Abstract Obtaining electrodes with high electromigration resistance, which are used in high-frequency surface acoustic wave devices, is imperative for the rapidly developing mobile communications industry. The effect of a Ti underlayer on the electromigration resistance and texture of Al films was studied comprehensively. It was found that crystalline orientation, crystalline size and electromigration resistance varied significantly with the thickness of the Ti underlayer. A highly (1 1 1) oriented Al film with a full width at half maximum value of the rocking curve of 1.7° and a crystalline grain with a bamboo-like structure was successively deposited on an ultrathin titanium underlayer (∼1 nm). The median time to failure of Al interconnects with the ultrathin Ti underlayer was enhanced by one order of magnitude higher than those without the Ti underlayer. The influence of the Ti underlayer on the texture of Al films was investigated using a combination of X-ray diffraction and transmission electron microscopy techniques. The results revealed that the ultrathin discontinuous Ti underlayer facilitated the Al (1 1 1) texture growth. The mechanism of texturing was discussed in terms of surface-interface energy balance along with high resolution transmission electron microscopy analysis.