Recent progress on alternative metals for advanced interconnects

Abstract

With the continued downscaling of semiconductor devices such as transistors and memory, metal interconnects have become increasingly critical for transmitting the electrical signals required for data processing. Recently, metal interconnects have played a critical role in enhancing computing performance, particularly through advanced packaging technologies that accelerate the progress of artificial intelligence (AI) computing. Copper (Cu) is widely used as an interconnect material due to its low bulk resistivity of 1.68 μΩ·cm. However, as the physical dimensions of interconnects shrink below 10 nm, the resistivity of Cu increases significantly; a phenomenon known as the resistivity size effect. The increasing resistance of interconnects leads to resistance-capacitance (RC) delays, which decrease the operation speed of transistors and memory devices. Consequently, the rising resistance of metal interconnects at small dimensions hampers the progress of fast, efficient AI computing, where data volume has been growing exponentially. This increase in resistivity originates from enhanced electron scattering at surfaces and grain boundaries at reduced physical dimensions. To overcome the resistivity size effect, metals with short electron mean free paths (EMFPs) are required to reduce scattering. Therefore, the exploration of alternative interconnect materials is essential. In this review, we address the requirements for advanced interconnect materials and compare the properties of potential candidates for reducing RC delays. We also summarize the challenges in developing alternative metals and fabrication methods, categorized into single-elementary metals, binary intermetallic compounds, ternary metals, and emerging topological semimetals. Finally, we provide an outlook on the development of next-generation interconnect materials.