Enabling the 2.5D Integration

3D IC is the viable revolutionary technology that will enable system-level integration, miniaturization, optimal power management, increased data bandwidth, and eventually reduced system cost. Like any breakthrough technologies, it faces many challenges. Design methodology, integration technology, manufacturing process and new industrial ecosystem are the areas of focus. This paper will discuss these challenges and Altera's 3D integration development effort. 2.5D is an intermediate path to true 3D IC using silicon interposer and TSV (Through-Si-Via) stacking. The 2.5D stacking configuration offers different form factor, interconnect path, and thermal management options than monolithic packages, which could help to reduce system level power and thermal management pressure. It offers silicon level interconnect density, low inductive path and wide IO application. However, it's power delivery system (PDN) could be the bottleneck for the system to perform at the intended bandwidth and speed. Thus, the whole system, IC-Interposer-Package-PCB, must be considered holistically, and trade off study and compensation mechanism development are needed in such complex system level integration. There are many different 2.5D integration manufacturing flows currently under development. They can be categorized into two major flow options: Attaching interposer to substrate first, which can be called CoCoS (Chip on Chip on Substrate); or attaching device silicon to interposer first, which is also called CoWoS (Chip on Wafer on Substrate). The major challenges are in the areas of manufacturing process window and yield, thin wafer handling, testability and overall cost of the integration process. ,). This paper will discuss design consideration, manufacturability analysis, Logic/memory devices and silicon interposer interaction, and thermal management to enable the 2.5D integration. System level characterization and correlation with simulations are performed. The challenge of new supply-customer model and industrial ecosystem development associated with 2.5D integration will also be discussed.