Defining Heterogeneous Integration

Introduction

Marvell’s recent paper "2.5D Heterogeneous Integration for Silicon Photonics Engines in Optical Transceivers" discusses the concept of heterogeneous integration and its benefits for optical transceivers in cloud data centers. In this podcast, Radha Nagarajan, SVP and CTO of Marvell's Optical and Copper Connectivity Group, is interviewed to provide more details on heterogeneous integration and its applications.

Defining Heterogeneous Integration

Heterogeneous integration refers to combining materials or components from different sources onto a common substrate. In silicon ASICs, it means integrating chips from different foundries or even different technologies onto a single substrate to form a highly integrated system.

The white paper focuses on integrating silicon photonics with silicon germanium amplifiers and III-V lasers. This showcases heterogeneity in terms of varied materials (silicon, SiGe, III-Vs) and foundries. Bringing the strengths of these different technologies together enhances overall system performance.

Benefits of Heterogeneous Integration

Nagarajan highlights several benefits of heterogeneous integration:

1. Overcomes limitations of monolithic integration: A single technology cannot provide all required functionality. Heterogeneous integration allows picking the most optimal technology for each component.

2. Commercial benefits like supply chain diversity and shortened cycle times from splitting across foundries.

3. Technical performance benefits from selectivity - e.g. SiGe offers better analog performance than CMOS. Lasers need III-V materials.

Impact on Cloud Data Centers

Nagarajan discusses four main impacts of heterogeneous integration for cloud data centers:

1. Enables higher bandwidth optical links by allowing tighter integration and lower losses between components.

2. Saves power from board-level interconnects through integration on a common substrate. Improves energy efficiency.

3. Realizes more advanced functionality not previously possible.

4. Provides latency benefits from tighter integration between processing and optical I/O elements. Enables more efficient computing architectures.

Use Cases

Two key use cases are covered:

1. Co-packaged optics: Integrating optical I/O elements like silicon photonics directly with electronic chips like GPUs or AI accelerator dies. Eliminates communication bottlenecks.

2. Integrating memory and processors: Placing DRAM chips right next to processors using advanced packaging like HBM achieves higher bandwidth and lower latency.

In both cases, heterogeneous integration provides performance, power and efficiency benefits by allowing tight co-integration of best-in-class technologies.

Figure 1. Marvell’s definition of 2D, 2.5D and 3D integration in the paper.

Conclusion

Heterogeneous integration offers significant advantages for cloud data center infrastructure by enabling optical engines and electronic chips or memory and processors to be co-packaged. This provides an optimal combination of technologies to overcome integration limitations and achieve gains in bandwidth, latency, power efficiency and functionality. Marvell's white paper provides an excellent overview of the current state and future potential of this integration approach.