TABLE OF CONTENTS The power current requirements of integrated circuits are rapidly rising, as discussed in Chapter 1. The current density in on-chip power and ground lines can reach several hundred thousands of amperes per square centimeter. At these current densities, electromigration becomes significant. Electromigration is the transport of metal atoms under the force of an electron flux. The depletion and accumulation of the metal material resulting from the atomic flow can lead to the formation of extrusions (or hillocks) and voids in the metal structures. The hillocks and voids can lead to short circuit and open circuit faults [72], respectively, as shown in Fig. 4.1, degrading the reliability of an integrated circuit.
The significance of electromigration has been established early in the development of integrated circuits [73], [74]. Electromigration should be considered in the design process of an integrated circuit to ensure reliable operation over the target lifetime. Electromigration reliability and related design implications are the subject of this chapter. A more detailed discussion of the topic of electromigration can be found in the literature [75], [76].
The chapter is organized as follows. The physical mechanism of electromigration is described in Section 4.1. The role of mechanical stress in electromigration reliability is discussed in Section 4.2. The steady state conditions of electromigration damage in interconnect lines...
