Lecture 12 Electromigration iMechanica（讲座12电迁移iMechanica）.pdfVIP

Spring 2004 Evolving Small Structures Z. Suo Lecture 12 Electromigration This lecture is an abbreviated version of a section in the following article. A PDF file of the article is available online at /suo , Publication 139. Z. Suo, Reliability of interconnect structures. pp. 265-324 in Volume 8: Interfacial and Nanoscale Failure (W. Gerberich, W. Yang, Editors), Comprehensive Structural Integrity (I. Milne, R.O. Ritchie, B. Karihaloo, Editors-in-Chief), Elsevier, Amsterdam, 2003. Electromigration in interconnects. In service, an interconnect line carries an intense electric current. The conduction electrons impact metal atoms, and motivate the atoms to diffuse in the direction of electron flow. The process, known as electromigration, has been the most menacing and persistent threat to interconnect reliability. SiO2 TiAl3 SiO2 Al SiO2 TiAl W SiO2 3 W Consider an aluminum line encapsulated in a silica dielectric. The tungsten vias link aluminum lines between different levels. The titanium aluminide layers shunt the electric current where voids deplete a segment of aluminum. On cooling from the deposition temperature, thermal expansion misfit causes a tensile stress in aluminum. Voids may grow in the aluminum line. Each void relaxes the stress in its vicinity. After the line is subject to an electric current, the voids exhibit extraordinaril