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In situ study on low-k interconnect time-dependent-dielectric-breakdown mechanisms

: Yeap, Kong Boon; Gall, Martin; Liao, Zhongquan; Sander, Christoph; Mühle, Uwe; Justison, Patrick; Aubel, Oliver; Hauschildt, Meike; Beyer, Armand; Vogel, Norman; Zschech, Ehrenfried


Journal of applied physics 115 (2014), Nr.12, Art. 124101, 8 S.
ISSN: 0021-8979
ISSN: 1089-7550
Fraunhofer IKTS ()
electric breakdown; in situ processing; nanoparticles; constant voltage; interconnect stacks

An in situ transmission-electron-microscopy methodology is developed to observe time-dependent dielectric breakdown (TDDB) in an advanced Cu/ultra-low-k interconnect stack. A test structure, namely a "tip-to-tip" structure, was designed to localize the TDDB degradation in small dielectrics regions. A constant voltage is applied at 25°C to the "tip-to-tip" structure, while structural changes are observed at nanoscale. Cu nanoparticle formation, agglomeration, and migration processes are observed after dielectric breakdown. The Cu nanoparticles are positively charged, since they move in opposite direction to the electron flow. Measurements of ionic current, using the Triangular-Voltage-Stress method, suggest that Cu migration is not possible before dielectric breakdown, unless the Cu/ultra-low-k interconnect stacks are heated to 200°C and above.