Thermoreflectance Imaging of Electromigration in Aluminum Interconnects at Different Ambient Temperatures

Abstract Electromigration (EM) is the process of displacing atoms in metals due to current flow leading to interconnect failures in electronic circuits. As electronics feature sizes continue to shrink, EM is becoming an increasingly serious reliability concern. EM, in aluminum (Al) interconnects, has been studied previously, but typically on the device level using Black’s law [1], without emphasis on the localized heating and defect generation around the failure site. To better understand the local EM process, thermoreflectance (TR) thermal imaging technique is used to obtain temperature profiles with submicron resolution [2]. We show that a simple lifetime prediction using Black’s law is not possible for a micro Al wire having a patterned constriction. The wire fails at two distinct failure locations depending on the level of current excitation. Moreover, the lifetime dependence on ambient temperature was studied. Each failure location had its own extracted activation energy. Our findings suggest that Black’s law may be extended to local features. They also show the potential for the design of local features in extending the lifetime of metallic interconnects. In summary, the temperature profile with submicron spatial resolution offers a unique opportunity to better understand the different mechanisms contributing to EM failures which can be used to design highly reliable interconnects.