The Role of Texture On The Reliability Of Aluminum Based Interconnects

Abstract

AbstractPreferred crystallographic orientation has long been recognized to play an important role in interconnect reliability where a strong (111) texture improves electromigration lifetime. Detailed microstructural analyses have enabled the role of texture to be better understood. Although Bragg-Brentano scans are often used to characterize texture, it is shown that this technique gives incomplete and sometimes misleading information. The pole figure technique provides a complete description of the texture. The measurement and presentation of textures consider experimental aspects unique to thin film analysis as a prerequisite to developing quality data. Five textural archetypes are identified, and metrics presented for their quantification. Processing effects on texture are complex and depend on all facets of deposition conditions, on substrate/underlayers, and on annealing. General trends and specific examples of the impact of each aspect are given where it will be shown that deposition conditions and the presence of underlayers have the greatest influence. The role of texture on reliability is considered for four failure modes: thermal hillocks, grain collapse, stress voiding, and electromigration. Electromigration results are emphasized where texture must be considered in the context of grain structure, in general, and, more specifically, the ratio of line width to grain size. Most measures of microstructure and reliability are statistical. The importance of local microstructural analysis will be emphasized in terms of both the arrangement of grains relative to the line dimension and microtexture characterization of the grain-to-grain misorientations.