This issue of the MRS Bulletin focuses on current interconnect metallurgies practiced in the manufacturing of integrated circuits (ICs). The issue should serve as a reference for researchers, scientists, engineers, and those who are not familiar with the IC arena.

Al-metallization requires special attention due to its wide usage in logic and memory circuits. Logic requirements drive technology toward improved circuit performance while memory improvements require high device and wiring densities. As the dynamic random access memory (DRAM) evolves from 64 Mbits to 256 Mbits, ultralarge-scale integrated (ULSI) wiring will decrease to below sub-0.3 μm in dimensions. Such circuits require robust, reliable back end of the line (BEOL) technology that meets high-performance, low-cost, stringent electromigration requirements. We feel that several of these emerging interconnect fabrication techniques have reached a sufficient level of maturity to warrant a reasonable exposition. We will concentrate on metallization systems in this issue, leaving a discussion of dielectrics for the future, due to space limitations.

The semiconductor industry has relied on aluminum technology since the 1960s because it is a well-established, low-cost technology. Early improvements in the electromigration resistance of Al lines by the addition of Cu impurities after 1971 helped this metallurgy to endure further feature size reductions, without degradation of reliability. However, the relentless reduction in via and line size once again may bring into question the limitation of Al reliability. As a result, work on alternate low-resistivity and high-electromigration-resistant metals like Cu is continuing in parallel.