In the world of semiconductors and microelectronics, a trend to vertically stack integrated circuits (ICs) or circuitry has emerged as a viable solution for meeting electronic device requirements such as higher performance, increased functionality, lower power consumption, and a smaller footprint. The various methods and processes used to achieve this are called 3D integration technologies.
Next-generation platforms are evolving rapidly to keep pace with emerging system trends driven by an explosion of applications such as data center capabilities, Internet of Things (IoT), 400G to terabit networking, optical transport, 5G wireless, 8K video, etc. The resulting expansion of connectivity and processing will affect the semiconductor space significantly, from the type of components that are built to higher efficiency systems and related services.
A close evaluation of this emerging landscape reveals some interesting trends. For example, next-generation data center workloads demand increasingly higher computational capabilities, flexibility, and power efficiencies; outstripping the capabilities of today’s general-purpose servers. Additionally, data center infrastructure must be virtualized and delivered as a service over commodity servers to reduce complexity and provide greater business agility and scalability. However, server performance improvements have actually slowed, primarily due to power limitations. Designing data center solutions for specific workloads increases efficiency but significantly limits the homogeneity and flexibility of the solution. Flexibility is crucial because data center services evolve rapidly and require adaptable hardware. As a result, the challenge for next-generation data center platforms is to deliver higher performance (acceleration), power efficiency, and flexibility simultaneously.
IoT reflects similar challenges. IoT is projected to grow dramatically and hit the multibillion “smart objects” mark in the near future. These smart objects are connected and communicate with each other or to a cloud or data center. The infrastructure must determine which data needs to be processed and which data is dropped, all in real time. Therefore, IoT requires a highly connected, flexible, efficient, bandwidth-rich infrastructure that enables insight from the data center to the edge. This requirement challenges service providers, data centers, cloud computing, and storage systems to satisfy this insatiable demand for Internet traffic.
Thus, system architects designing next-generation platforms must try to meet the following requirements:
■ Higher bandwidth
■ Lower power
■ Smaller footprint or form factor
■ Increased functionality
■ Increased flexibility
3D integration technology has become the most widely used technology to achieve the above said requirements.
What is 3D Integration?
There are certainly different understandings in the microelectronics community regarding the definition of heterogenous 3D integration. In a very general definition, it is defined as the 3D integration of different devices such as a CMOS processor and a memory, for example. A more limiting specification would define it as the integration of different substrate materials necessary for the condition (e.g. GaAs / silicon). For the purpose of this article, we will define it as the 3D integration of components with significant different device technologies as e.g. CMOS and MEMS.