【Spotlight】Revolutionizing AI Chips RDL Interposer Explained

In this series on 3D integration technology, we will explore RDL Interposer, a technology that significantly influences semiconductor performance alongside miniaturization.

About RDL Interposer

RDL Interposer (Redistribution Layer Interposer) is a type of 2.5D packaging technology using an interposer substrate, part of advanced packaging technologies.

It involves creating a redistribution layer (RDL) on a resin substrate to arrange chipletized dies on the same plane for interconnection.

The most notable feature of RDL Interposer is its lower manufacturing cost compared to Si Interposer, as it uses a resin substrate, making it cost-efficient.

Currently, 2.5D packaging using Si Interposers with RDL wiring on silicon substrates is prevalent in advanced applications like AI and HPC. However, the high manufacturing cost of Si Interposers, which are produced via wafer front-end processes, increases the total package cost.

Additionally, the push for higher integration and larger die sizes in advanced devices has led to limitations for Si Interposers, such as performance degradation due to increased interposer size and a maximum size of 12 inches.

In this context, RDL Interposer, which offers lower production costs, better electrical characteristics, and the ability to be larger than Si Interposers, has seen adoption in certain applications alongside silicon bridge technologies.

Illustration of RDL Interposer

Comparison of Si Interposer and RDL Interposer

Challenges and Future Prospects of RDL Interposer

Challenges:

1. Thermal Management:
   • Increased integration leads to heat issues, especially with high-performance processors or GPUs.
   • Advanced materials or 3D stacking may aid efficient heat dissipation.
2. Cost Efficiency:
   • While RDL Interposers are cost-effective, further reductions are needed for consumer and IoT devices.
3. Manufacturing Complexity:
   • Microfabrication and multilayering complicate production, risking cost increases and yield losses.
4. Material Reliability:
   • Durability under extreme conditions remains a concern. Developing robust materials is critical.

Future Prospects:

• New Materials and Techniques: Advanced lithography and nano-fabrication may improve precision and cost-effectiveness.
• Expanding Applications: Beyond mobile and IoT markets, RDL Interposer can be applied in automotive and medical fields.
• Broader Market Use: With innovation in heat management and production, RDL Interposers are expected to see wider adoption in various fields.

Glossary

• Advanced Packaging Technology: Technologies enabling dense integration for improved performance and power efficiency, including 3D stacking and System-in-Package (SiP).
• Si Bridge Technology: A method connecting semiconductor chips via a silicon substrate for high-density and efficient electrical connections.
• Permittivity: A measure of a material’s ability to polarize in response to an electric field, affecting its electrical characteristics.

Download a Document
Visual Inspection of Semiconductor Wafers

Download

Download a Document
The Next Dimension of Semiconductors: Exploring Advanced Packaging

Download