Evaluating the Large Electromigration Resistance of Copper Interconnects Employing a Newly Developed Accelerated Life‐Test Method

Abstract

An accelerated electromigration life‐test method has been developed to evaluate the large electromigration resistance of Cu interconnects in a very short period of test time. The essence of the acceleration technique employed here is to use stress current more than 107 A/cm2 and to utilize the self‐heating of the test interconnect for giving temperature stress. Moreover, to avoid uncontrollable thermal runaway and resultant interconnect melting, we adopted an efficient cooling technique that immediately removes the joule heat and keeps the interconnect temperature constant. As a result, it has been demonstrated that large grain copper interconnects created by a low‐kinetic‐energy particle process and the thermal annealing that follows exhibit approximately three orders of magnitude larger electromigration lifetime at 300 K than Al‐alloy interconnects formed by a conventional sputtering process. Additionally, a new expression for electromigration lifetime was proposed based on Black's equation through the comparative studies of electromigration endurance of various materials.