As AI-driven High-Performance Computing (HPC) evolves, the semiconductor industry is facing increasing packaging challenges. To keep pace with growing I/O bandwidth requirements, processors must communicate with High Bandwidth Memory (HBM) and neighboring chiplets at unprecedented speeds.
While chiplet-based architectures offer a promising path toward higher performance and improved scalability, they also place new demands on advanced packaging technologies. One key requirement is the continued shrinking of Redistribution Layer (RDL) features to provide the interconnect density needed to reduce 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 one of the emerging directions in advanced packaging research: the exploration of glass substrates as a potential platform for future high-density packaging.
Why Glass? Exploring the Path Beyond Sub-2 µm Features
Today’s high-density RDLs are commonly built using Ajinomoto Build-up Film (ABF) on organic cores. However, as the industry investigates ultra-fine features (sub-2 µm lines and spaces), researchers and manufacturers are evaluating multiple approaches for improving dimensional stability, surface quality, and scalability. Glass substrates are attracting significant attention as one possible option.
Two of the key motivations behind this research are:
- Surface Roughness & Planarity: At very fine geometries, substrate surface quality becomes increasingly important. Glass offers an exceptionally smooth and planar surface, which may help support more uniform deposition processes and tighter line/space dimensions.
- Dimensional Stability: Large-format substrates experience thermal and mechanical stress during processing. Compared to many organic materials, glass can offer high rigidity and strong thermal stability. It also enables closer matching of the Coefficient of Thermal Expansion (CTE) to silicon, which may help reduce stress during thermal cycling for large AI and HPC packages.
At the same time, major challenges remain — including manufacturability, handling, Through-Glass Via (TGV) integration, ecosystem readiness, and cost-effective scaling to production volumes. The long-term adoption timeline for glass substrates is still evolving, and the industry continues to explore multiple material and process approaches in parallel.
A Collaborative Ecosystem: Advancing Advanced Packaging with IZM and Georgia Tech
Advanced packaging is too complex for any one company to solve in isolation. Heidelberg Instruments is proud to contribute to collaborative ecosystems that bridge the gap between R&D, pilot line development, and future industrial production.
- The Glass Panel Technology Group (GPTG): Led by Fraunhofer IZM, this consortium of industrial and R&D partners works across 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, Heidelberg Instruments contributes to research focused on future packaging roadmaps and increasingly fine line/space dimensions on panel-level glass substrates.
How Maskless Lithography Enables the "Glass Core"
The exploration of glass substrates requires flexible lithographic workflows, rapid process iteration, and adaptive patterning capabilities. This is where Heidelberg Instruments’ MLA 300 Maskless Aligner and VPG series support advanced packaging R&D, pilot lines, and mid-volume production environments.
Adaptive Alignment and Distortion Compensation
Even rigid substrates such as glass can experience microscopic distortions during processing steps like dielectric lamination. Maskless lithography enables real-time alignment correction by imaging the substrate and adapting the digital pattern during exposure. This helps improve overlay accuracy between RDL patterns and TGV structures across large-format panels.
Enabling Process Exploration
Heidelberg Instruments systems support the evaluation of emerging process flows, including Semi-Additive Processes (SAP), advanced dielectric materials, and photopatternable dielectrics (PPDs) for Damascene processing approaches.
The flexibility of maskless lithography allows engineers to iterate designs quickly, evaluate new materials efficiently, and adapt process parameters without requiring new photomasks for every design revision.
Supporting Future Scaling
While much of the industry focus today is centered around 2 µm line/space dimensions, research roadmaps continue toward even finer geometries. Heidelberg Instruments’ maskless platforms support process development for these future requirements while enabling large-area exposure strategies for panel-level packaging formats up to 510 mm × 515 mm.
Sustainability and Efficient Process Development
At Heidelberg Instruments, technical innovation goes hand-in-hand with the LAB14 sustainability agenda. The dimensional stability of glass and adaptive lithography workflows help reduce material waste during process development and prototyping by minimizing mask iterations and enabling faster optimization cycles. In addition, the panel-level approach allows for more efficient area usage.
By achieving higher interconnect density with fewer build-up layers, the consumption of chemicals and dielectrics can be lowered, creating a more resource-efficient production cycle and improving overall manufacturing efficiency in future advanced packaging flows.
Conclusion: Shaping the Future of Advanced Packaging
Glass substrates represent one of several promising directions being explored for next-generation advanced packaging. While significant technical and manufacturing challenges remain, ongoing collaboration across the semiconductor ecosystem is accelerating research and process development.
Through its work with consortia led by Fraunhofer IZM and Georgia Tech, Heidelberg Instruments positions itself as an enabler of advanced packaging R&D, pilot line development, process exploration, adaptive patterning, and future production scaling.
Are you exploring new advanced packaging approaches? Visit the advanced packaging page or contact our experts directly to learn how the MLA 300 can support your development and production goals.
