Microinterconnects

Microinterconnects are the conductive networks that connect active devices and components within microelectronic devices, most notably integrated circuits. They consist of metal lines and vias embedded in dielectric layers, forming a multilayer interconnect stack that routes signals and power between transistors, capacitors, and I/O pads. As device features shrink, interconnects become a dominant source of resistance, capacitance, and delay, influencing overall circuit performance.

Materials and fabrication: Copper has become the standard interconnect metal in modern CMOS processes, replacing aluminum due to superior electromigration resistance and lower resistivity. Copper is surrounded by diffusion barriers and adhesion layers, such as tantalum nitride or titanium nitride, to prevent diffusion into surrounding dielectrics. Dielectrics with low dielectric constant (low-k) help reduce capacitance. Interconnects are formed by deposition of metal films, patterning via photolithography, etching to define lines, and chemical-mechanical planarization to create a flat surface. Vertical connections between layers are made with vias; in advanced configurations, through-silicon vias (TSVs) enable 3D stacking.

Reliability and design: Key concerns include RC delay, electromigration, stress-induced voiding, and crosstalk. Thermal management and mechanical stresses from mismatched coefficients of thermal expansion are also critical. Design practice incorporates electromigration-aware layouts, impedance control, and signal integrity analysis.

Extensions: In 3D integration and heterogeneous packaging, microinterconnects extend across multiple dies or into interposer substrates, enabling higher density and heterogeneous functionality. Ongoing research explores alternative materials and architectures to scale interconnect performance alongside device scaling.