The Effects of Al(111) Crystal Orientation on Electromigration in Half-Micron Layered Al Interconnects

A study has been done on the crystallographic effects of under-metal planes on Al(111) orientation in layered Al interconnects (Al/Ti, Al/TiN/Ti), and the dominant factor for electromigration was clarified in the region below a half-micron line width. It was found that Al(111) preferred orientation is strongly dependent on the crystal structure and process sequence of the under-metal, and universally determined by the difference between the spacing of Al(111) plane and under-metal planes. Moreover, it was found that the electromigration endurance tends to improve in proportion to the degree of Al(111) preferred orientation. Therefore, the formation of an under-metal layer with an appropriate plane whose spacing is close to that of the Al(111) plane is the most significant criterion for the realization of highly oriented Al(111) planes and hence highly reliable ULSI interconnects.