AI is hitting a hardware wall. As AI-driven High-Performance Computing (HPC) evolves, the semiconductor industry faces a critical bottleneck. To keep pace with massive I/O bandwidth requirements, processors must communicate with High Bandwidth Memory (HBM) and neighboring chiplets at unprecedented speeds.
While chiplet-based architectures offer a path to economic viability, they demand a new foundation for advanced packaging. Specifically, we must shrink Redistribution Layer (RDL) features to provide the density of interconnects required to prevent data bottlenecks.
In our previous post, “The Die is Not Enough,” we explored how maskless lithography corrects patterns on the fly and writes beyond standard reticle sizes. Today, we look at the next frontier: the industry-wide transition from traditional organic substrates to glass substrates.
Why Glass? Breaking the Sub-2 µm Barrier
Traditional high-density RDLs are built using Ajinomoto Build-up Film (ABF) on organic cores. However, as the industry pushes toward ultra-fine features (sub-2 µm lines and spaces), organic materials are hitting a physical ceiling due to two factors:
- Surface Roughness & Planarity: At a microscopic scale, organic substrates are “rough.” When RDL metal traces become ultra-thin, the microscopic “peaks and valleys” of the substrate prevent uniform deposition. This leads to metal bridging and electrical shorts.
- Dimensional Stability: Organic cores warp under thermal stress. In contrast, glass is exceptionally rigid and thermally stable. It allows engineers to match the Coefficient of Thermal Expansion (CTE) to silicon. This reduces mechanical stress during thermal cycling, drastically improving the reliability of the massive dies used in AI.
A Collaborative Ecosystem: Leading the Charge with IZM and Georgia Tech
Advanced packaging is too complex for any one company to solve in isolation. Heidelberg Instruments is proud to bridge the gap between R&D and industrial production through two primary consortia:
- The Glass Panel Technology Group (GPTG): Led by Fraunhofer IZM, this group of industrial and R&D partners works on the entire process chain for large-format glass-core substrates – from Through-Glass Vias (TGV) and Redistribution Layers (RDL) to assembly. “We are scaling up and adapting high-precision semiconductor processes to large, cost-effective rectangular glass panels,” says Ruben Kahle, leader of the Embedding & Substrate Technologies (EST) group at Fraunhofer IZM.
- 3D Systems Packaging Research Center (3D-PRC): In collaboration with Georgia Tech, we are defining the technical roadmaps for the finest lines and spaces (L/S) ever achieved on glass.
How Maskless Lithography Enables the "Glass Core"
The transition to glass requires a level of lithographic flexibility that traditional mask-based systems simply cannot provide. Our MLA 300 Maskless Aligner and VPG series are the engines of this revolution.
Precision Adaptive Alignment
Even with the rigidity of glass, large-format panels experience microscopic distortions during dielectric lamination. Maskless lithography is the only technology capable of real-time correction. Our systems image the substrate in real-time and adjust the digital pattern on the fly, ensuring perfect alignment between RDL patterns and TGVs across the entire panel.
Pushing Process Limits
We are currently testing the boundaries of Semi-Additive Processes (SAP) and exploring photopatternable dielectrics (PPDs) for Damascene processing. By evaluating new materials at the panel level, we are paving the path toward higher density and thinner dielectric layers.
Future-Proofing for Sub-Micron Features
While the industry is currently focused on 2 µm L/S, the roadmap is moving toward sub-micron dimensions. Our maskless platforms are already capable of delivering this resolution, solving the primary challenge of scaling high-throughput production to full panel sizes (up to 510 mm x 515 mm).
Sustainability: The LAB14 Agenda
At Heidelberg Instruments, technical performance goes hand-in-hand with the LAB14 sustainability agenda. Transitioning to glass supports a greener manufacturing future. The dimensional stability of glass reduces material waste, and the panel-level approach allows for more efficient area usage. By achieving higher interconnect density with fewer build-up layers, we directly lower the consumption of chemicals and dielectrics, creating a more resource-efficient production cycle.
Conclusion: Shaping the Future of Semiconductors
The shift to glass substrates will define the next decade of semiconductor innovation. Through our work within the consortia led by Fraunhofer IZM and Georgia Tech, Heidelberg Instruments is ensuring that the fabrication tools are ready for the next generation of AI hardware.
Are you ready to scale your advanced packaging capabilities? Visit our advanced packaging page or contact our experts to learn how the MLA 300 can transform your production line.
