21 May 1993 Three-dimensional finite element calculations of thermal stress in aluminum interconnect with tungsten via-studs
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Abstract
The multilevel interconnect to be investigated consist of a first level aluminum line (M1) connected to a second level aluminum line (M2) by a tungsten via-stud (S1). In the manufacturing process, thermal voiding is often observed in passivated aluminum lines near the via-stud. The purpose of this work is to calculate the thermal stresses in a typical passivated multilevel metal-stud-metal structure using the finite element method. Variations of stresses with the tungsten via-stud intersect area, height, and its alignment with respect to M1 have been considered. It is shown that the local stresses in the aluminum line (M1) increase by 25%, the maxima located under the tungsten via-stud. The stresses further increase if the via- stud is misaligned to abut the end of the line. The average stress in the line is not significantly influenced by variation in stud dimensions of 30% about the nominal case, indicating that the stress response is dominated by the passivation. Higher stresses are calculated for SiNx passivation as compared to SiO2 since the former is twice as stiff.
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Lloyd G. Burrell, Lloyd G. Burrell, Amit X. Kapur, Amit X. Kapur, } "Three-dimensional finite element calculations of thermal stress in aluminum interconnect with tungsten via-studs", Proc. SPIE 1805, Submicrometer Metallization: Challenges, Opportunities, and Limitations, (21 May 1993); doi: 10.1117/12.145479; https://doi.org/10.1117/12.145479
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