Data transmission is becoming more and more critical in HPC application and traditional copper wire is limited by bandwidth, distance and power requirement. Silicon photonics is a promising technology to replace copper wire and it provides greater bandwidth, longer transmission distance and better energy efficiency. As a result, silicon photonics technology will be widely adopted for optical transceiver or on-board/co-packaged optics in future hyperscale datacenter.
What is Silicon Photonics? Advantages of Silicon Photonics?
Briefly speaking, silicon photonics (SiPh) acts as a medium to allow light travelling inside it. Thanks to modern semiconductor technologies, silicon photonics is able to leverage the existing complementary metal oxide semiconductor (CMOS) ecosystem including front-end and back-end processes to implement high density photonic integrated circuits (PIC) and enable complex optical functionality (ex: filtering or modulation) on a compact chip at low cost. Silicon photonic technology is convincing to transmit data with higher bandwidth and better energy efficiency than conventional electrical integrated circuits, which may suffer serious signal integrity distortion when transmit data at high speed.
The Evolution of Fiber Optics Integration
There are already silicon photonics based pluggable optical transceivers up to 800Gbps in commercial. Different with front-panel transceiver, optical engine can be populated around ASIC IC package as so-called on-board optics (OBO), which is able to support 1.6T Gbps. Additional to OBO, “Co-packaged Optics” and “Optical I/O” is promising to further shorten electrical paths with highly assembly integration, so that it is possible to deliver even higher bandwidth to ensure better energy efficiency (pJ/bit) and capital expenditure ($/Gbps) over pluggable optics.
The evolution of data transmission by replacing electrical circuits with optical path.
Silicon Photonics Technical Building Blocks
Unlike common semiconductor manufacture experiences, silicon photonics products may need more attentive consideration when defining the overall process flow to address optical performance. Here, we list key technologies to enable pluggable, on-board and co-packaged optics:
- Post-fab wafer-level bumping and Si-etch process
- High accuracy laser die bonding
- EIC*/PIC die integration (TSV/FO/CoW) to enable 2.5D/3D packaging
- Wafer-level optical probing test for known good SiPh PIC die
- Optical component assembly evaluation for future OBO*/CPO* application
- MCM module assembly
SiPh Based Pluggable Module Manufacturing Flow
Silicon Photonics Applications
Silicon photonics enables heterogeneous on-board optics, co-packaged optics and optical I/O packaging, which is promising to realize the following applications.
- Hyperscale Data Center
- High Performance Computing (HPC)
- Artificial intelligence & Machine learning (AI & ML)