Lookup NU author(s): Christopher Wilson,
Dr Alton Horsfall,
Professor Anthony O'Neill,
Professor Nick Wright,
Professor Steve Bull
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This paper reports the first direct experimental measurement of electromigration-induced stress in aluminum interconnects, using a series of microrotating stress sensors. The build-up of stress gradients in interconnect metallization, which is concomitant with backstress, has been previously investigated theoretically, but experimental verification using optical or X-ray techniques has proven more difficult. These initial results show a compressive-stress gradient along the line of stress sensors, consistent with that predicted by conventional mass-transport theory. Additionally, these measurements are in qualitative agreement with the mathematical model proposed by Korhonen et al. (1993), with a reduced-stress and increased-diffusion coefficient. These differences are discussed, and the causes postulated. The limited resolution of previous techniques restricts their ability to obtain a detailed characterization, whereas, in principle, this new technique can be scaled to the end of the International Technology Roadmap for Semiconductors. These preliminary findings suggest that the presented technique will provide a valuable tool for the investigation of back-end-of-line interconnect stress in the future. © 2007 IEEE.
Author(s): Wilson CJ, Horsfall AB, O'Neill AG, Wright NG, Bull SJ, Terry JG, Stevenson JTM, Walton AJ
Publication type: Article
Publication status: Published
Journal: IEEE Transactions on Device and Materials Reliability
Print publication date: 01/06/2007
Date deposited: 26/05/2010
ISSN (print): 1530-4388
ISSN (electronic): 1558-2574
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