diestacking

Die stacking, or die-stacking, is the practice of placing two or more semiconductor dies in a single integrated package so that they operate as a single device. This approach increases functional density and bandwidth while reducing interconnect length compared with traditional side-by-side packaging. Die stacking is a core technique in the development of 3D integrated circuits and heterogeneous integration, and it is applied in both memory and logic stacks.

Technologies used to connect stacked dies include through-silicon vias (TSVs), microbumps, and wafer or die bonding. Common architectures include package-on-package (PoP), where a memory or logic die is stacked atop another die inside a standard package; 3D integrated circuits that wire-connect dies through TSVs; and interposer-based solutions that route signals from multiple dies to a common package. High Bandwidth Memory (HBM) exemplifies die-stacking, with several memory dies stacked and interconnected with a logic layer via an interposer or vertical interconnects.

Benefits include improved bandwidth and performance due to shorter interconnects, higher memory density, or compact form factors; enables heterogeneous integration by pairing different technologies in a single package; and can reduce system power and footprint in some configurations. Applications include smartphones, graphics processors, accelerators, and data center accelerators.

Challenges encompass thermal management, since stacked dies can concentrate heat; manufacturing complexity and lower yields due to stacking; higher upfront cost and more stringent testing; reliability concerns such as interconnect fatigue; and equipment and process maturity that vary by technology.