Glass gains attention in the AI hardware race

As AI accelerates demand for more powerful semiconductor architectures, advanced packaging has become a critical battleground for improving performance, bandwidth and energy efficiency. Among the materials attracting growing industry attention is glass, offering a unique combination of dimensional stability, electrical performance and scalability for next-generation packaging. In this conversation, Phil Alsop, Contributing Editor of Advanced Packaging Magazine, speaks with Colin Schmucker, Global Sales and Product Manager for SCHOTT’s Semicon Glass Solutions, about why glass is emerging as an enabling material for advanced packaging, the role of SCHOTT’s “Semicon next” knowledge hub, and the opportunities and challenges that lie ahead.

Phil Alsop: SCHOTT recently launched “Semicon next” as a knowledge hub. What prompted this initiative, and what conversations are you hoping to drive within the semiconductor industry?

Colin Schmucker: Interest in glass for semiconductor applications has grown rapidly over the past few years, but many engineers and decision-makers are still unfamiliar with its capabilities as an advanced materials platform. When SCHOTT established its Semicon Glass Solutions business in 2024, one of our priorities was to help educate the industry about where glass can add value.

The semiconductor industry has always benefited from open knowledge sharing, so Semicon next was created to provide an accessible educational resource. The first modules introduce the fundamentals of glass and explain why it is attracting so much attention. Future content will dive deeper into specific applications, materials science and manufacturing technologies as the industry continues to evolve.

Phil Alsop: Advanced packaging has become one of the biggest areas of innovation in AI hardware. Where do you see glass fitting into this evolution?

Colin Schmucker: There are two major areas where glass is already making an impact.

The first is as a carrier for advanced fan-out packaging, particularly fan-out panel-level packaging. As AI devices become larger and more complex, manufacturers need extremely stable carrier materials capable of supporting high-volume processing while maintaining excellent dimensional stability. Glass provides that foundation.

The second area attracting significant attention is glass-core substrates (GCS). Here, glass forms the core of an organic substrate stack rather than acting as a temporary carrier. As AI processors continue to grow in size and complexity, glass offers the dimensional stability needed to manufacture larger substrates while maintaining flatness and reliability throughout processing.

Phil Alsop: What makes glass such an attractive material for these next-generation semiconductor packages?

Colin Schmucker: Several material properties come together.

One of the most important is stiffness. Modern packages combine many different materials, each expanding differently as temperatures change. A stiff glass core helps minimise warpage, which directly improves reliability.

Glass also offers highly tunable coefficients of thermal expansion (CTE), allowing manufacturers to better match the thermal behaviour of surrounding materials within the package.

Another major advantage is manufacturability. Glass supports extremely precise through-glass vias (TGVs), enabling high interconnect densities that are becoming essential for advanced AI devices.

Finally, its electrical properties are particularly attractive. Glass has a relatively low dielectric constant, very low electrical loss and an exceptionally smooth surface. Together these reduce signal attenuation and improve high-speed signal transmission, helping designers extract maximum performance from increasingly demanding AI systems.

Phil Alsop: Chiplet-based architectures are becoming central to heterogeneous integration. How does glass support this trend?

Colin Schmucker: Chiplets are really part of the broader move toward 2.5D and 3D heterogeneous integration. Although individual dies become smaller, the overall package becomes larger and more complex because multiple functional blocks are integrated together.

That requires finer redistribution layers, higher interconnect densities and exceptional dimensional control.

Glass provides the flatness, structural stability and processing precision needed to manufacture these increasingly dense interconnect structures. Whether used in glass-core substrates or advanced fan-out packaging, it enables manufacturers to integrate many active and passive components into a single high-performance package while maintaining tight manufacturing tolerances.

Phil Alsop: AI workloads demand enormous amounts of high-speed data movement. How does glass contribute to improved signal performance?

Colin Schmucker: Glass performs extremely well electrically. Its low dielectric loss minimises signal degradation as signals travel through the substrate, while its exceptionally smooth surface reduces losses caused by surface roughness, particularly at higher frequencies.

Looking further ahead, one of the most exciting opportunities is co-packaged optics. Glass isn’t simply an excellent electrical substrate it also has tremendous potential as an optical platform.

As optical communication moves closer to processors, glass could support optical interposers and optical bridges capable of integrating waveguides alongside electronic components. That opens the door to dramatically increasing chip-to-chip and package-to-package bandwidth while reducing overall power consumption.

Phil Alsop: Another characteristic frequently associated with glass is dimensional stability. Why is that becoming increasingly important?

Colin Schmucker: As interconnect dimensions continue to shrink, manufacturing tolerances become much tighter. Producing ultra-fine redistribution layers requires an extremely flat and stable substrate throughout processing.

Glass naturally provides that stability because it is manufactured as a highly homogeneous material with very consistent properties across the entire panel. It can also be polished to extremely low total thickness variation, allowing precise layer alignment throughout multiple processing steps.

This stability is equally valuable for advanced die stacking and hybrid integration, where maintaining accurate overlay between successive layers is essential for both manufacturing yield and long-term reliability.

Phil Alsop: Beyond signal integrity, glass is also recognised for its dimensional stability. How does that benefit increasingly dense semiconductor packages?

Colin Schmucker: As package complexity increases, manufacturers are pushing towards ever finer redistribution layers and interconnects. Achieving these ultra-fine geometries depends on having an extremely flat and dimensionally stable substrate.

Glass naturally provides that stability because it is manufactured as a highly homogeneous material with virtually no point-to-point variation. It also maintains its flatness throughout thermal processing and can be polished to extremely tight thickness tolerances. These characteristics help manufacturers achieve the precise overlay required for advanced redistribution layers, die stacking and high-density interconnects while maintaining long-term reliability.

Phil Alsop: Looking specifically at interconnect density, what role do you see glass playing in enabling the next generation of semiconductor packages?

Colin Schmucker: The trend is straightforward smaller line widths and spaces enable higher interconnect density, which ultimately improves package performance.

Glass contributes in several ways. Through-glass vias support very fine interconnect structures, while the material’s flatness allows increasingly precise redistribution layers to be built on top. Glass is also proving valuable as a carrier for hybrid copper bonding, where precise alignment is critical for stacking HBM memory and other advanced die-to-die architectures. As bonding pitches continue to shrink, the dimensional control offered by glass becomes increasingly important.

Phil Alsop: Glass has generated considerable excitement, but it is still not widely used as a substrate material. What challenges remain before broader adoption?

Colin Schmucker: It’s worth remembering that glass is already well established in several areas of semiconductor manufacturing. It’s been used for many years in MEMS, optoelectronics, sensor packaging and wafer processing, and more recently as a carrier for advanced fan-out packaging.

Glass-core substrates (GCS) represent a newer opportunity, but they introduce new manufacturing challenges. There isn’t yet a standard production process that everyone follows. Each substrate manufacturer is developing its own process flows, equipment and material combinations.

The industry has largely solved many of the fundamental engineering challenges, such as processing and handling glass, but attention is now shifting towards yield optimisation, cost reduction, process maturity and quality control. Manufacturers need confidence that glass-core substrates can be produced consistently, economically and with the long-term reliability required for AI systems.

Phil Alsop: Does accelerating adoption depend on greater collaboration across the semiconductor ecosystem?

Colin Schmucker: Absolutely. No single company can deliver this alone.

At SCHOTT, we understand glass extremely well, but advanced substrates involve many different materials, manufacturing processes and equipment suppliers. Glass manufacturers, substrate producers, equipment vendors and packaging specialists all need to work together to solve processing challenges and optimise manufacturing.

Collaboration is equally important for developing industry standards. Panel-level packaging is a good example. Standardising panel sizes allows equipment suppliers to develop manufacturing tools that can serve the wider industry rather than supporting numerous incompatible formats. That kind of cooperation ultimately accelerates adoption for everyone.

Phil Alsop: Finally, as AI processors continue to evolve, what milestones should the industry watch for that will signal glass becoming a mainstream packaging technology?

Colin Schmucker: The first major milestone will be the commercial deployment of glass-core substrates in production devices. Whether that begins with high-performance AI processors or smaller applications remains to be seen, but it will demonstrate that the technology is ready for commercial manufacturing.

The next milestone will be the introduction of larger glass-core packages that fully exploit the material’s advantages for high-performance computing. Those larger form factors represent one of the strongest value propositions for glass.

Ultimately, I think the industry is moving in that direction. Every major player is investigating glass in some form, and the technical benefits are becoming increasingly clear. There is still work to do around manufacturing and process optimisation, but the momentum is undeniable. As the industry continues to push for greater performance, bandwidth and efficiency, glass is well positioned to become one of the enabling materials for the next generation of advanced semiconductor packaging.