BackEndofLine

Backendofline, more commonly spelled as Back-End Of Line (BEOL), is a term used in semiconductor manufacturing to describe the portion of integrated circuit fabrication that occurs after the formation of the transistor structures in the front-end of line (FEOL). The term “backendofline” may appear in informal writing or searches as a variant of BEOL.

BEOL encompasses all processes involved in creating and wiring the interconnect network that connects transistors, as well as forming contact vias and the outer packaging pads. Its primary purpose is to establish electrical paths between devices on a chip and to provide routing for signals and power. BEOL steps typically include deposition of insulating dielectrics, patterning and etching of vias and metal layers, formation of barrier and seed layers, metallization (often copper with damascene processes), chemical mechanical planarization, and the application of passivation layers.

In modern BEOL flows, multiple metal layers are stacked to realize complex interconnect topologies. The lower metal layers (local interconnects) handle shorter, proximity routing, while higher layers (global interconnects) carry longer-distance signals. Materials choices, such as low-k dielectrics and copper interconnects, are common to reduce parasitic capacitance and RC delays. The BEOL also intersects with testing and reliability considerations, including electromigration resistance and diffusion barrier integrity.

Packaging and assembly are related domains that intersect BEOL decisions, though some classifications treat wafer-level packaging as part of BEOL and others consider it separate. BEOL efficiency and reliability are central to overall IC performance, power, and yield.