Aluminum-Based Metallurgy for Global Interconnects

Abstract

In an integrated circuit (IC), the global interconnects are used to run power and ground to the individual transistors as well as to send signals across the chip. The width of interconnects can vary, depending on the current that is carried by the interconnect. Figure 1 shows a cross section of a double-metal complementary metal oxide semiconductor (CMOS) circuit illustrating the major components of a multilevel metallization circuit. The global interconnect connects to the diffusion and polysilicon gates through the contacts. The intermetal dielectric electrically separates the different levels of interconnect. The connection between the global interconnects at adjacent levels is made through the vias. The choice of a global interconnect for a multilevel metallization forces one to consider how the interaction between the various components of this system can affect the performance of the interconnect. For example, the intermetal dielectric changes the mechanical stress in the interconnect; the presence of W plugs in vias can affect the electromigration resistance of interconnects. In this article, we will examine the problems that are encountered when using Al alloys as a global interconnect and illustrate how the material properties can be modified to solve these problems.