3DStacking

3D stacking refers to the integration of multiple semiconductor dies or components into a single package by stacking them vertically and interconnecting them with dense vertical interconnects. This approach aims to increase device density and performance by placing functions such as logic, memory, and accelerators in close proximity, reducing interconnect length and latency while enabling heterogeneous integration.

Two main pathways exist: 2.5D packaging, where dies sit side by side on a silicon interposer, and 3D stacking, which forms a vertical stack connected by through-silicon vias (TSVs) or microbumps. Bonding methods include die-to-die, die-to-wafer, and wafer-to-wafer bonding, with thinning and planarization to ensure reliable interconnections. Some approaches use interposers to organize the stack; others pursue direct 3D integration within a single substrate.

Applications span high-bandwidth memory stacks in GPUs and AI accelerators, and heterogeneous 3D-ICs for data centers, mobile devices, and embedded systems. Notable implementations include HBM memory stacks and packaging ecosystems such as Intel Foveros and various TSV-based interconnect schemes.

Benefits include higher density, increased inter-layer bandwidth, and potential power efficiency gains. Challenges include heat dissipation, process complexity, alignment and bonding precision, yield, testing, and cost.

3D stacking continues to evolve with advances in interconnects, materials, and packaging techniques, driving trends toward integrated heterogeneous systems and compact, high-performance devices.