• Effects of electromigration on the reliability of radio frequency microelectro mechanical switches

      Karri, Naveen Kishore (2004-12)
      Radio Frequency (RF) Micro-Electro-Mechanical System (MEMS) switches have many advantages over semiconductor switches. Despite these advantages they are not implemented in reliability demanding space, defense and commercial applications because of reliability concerns. Although some failure modes have been identified so far, other failure modes are still under research. Electromigration, a well-known failure mechanism in interconnects, was recently recognized as a possible cause of failure in micro-switches. However, there have been no instances of electromigration studies in the literature. This thesis presents a preliminary study on the electromigration failure and its impact on the lifetime of MEMS switches. A simulation program that emulates the electromigration process was developed. Parametric studies were performed to study the impact of impact certain parameters on electromigration process. The combined effects of Joule heating and electromigration were analyzed. Unlike passivated interconnects, the micro-switch is cantilevered and suspended in an inert medium without encapsulation. The electromigration lifetime estimation program developed in this thesis is applicable to all such free structures. Joule heating has been demonstrated to be a key factor in the electromigration failure of micro-switches. Results showed that the electromigration process is very slow at the beginning. After a certain time, the resistance is found to increase exponentially, increasing the temperature of the strip drastically toward failure. The same trend is also observed in a gold micro-switch, but with much slower rate of electromigration degradation, indicating a longer lifetime.