[Relevant Companies Mentioned in This Article] Corning, Schott, Sumitomo, Intel, TSMC (Taiwan Semiconductor Manufacturing Company), Samsung, Absolics, AGC, BOE
ECTC Conference: Corning Goes All-In on Glass Substrates Glass substrate technology has actually been gradually coming into the industry's focus since 2023, but it truly "arrived at the table" in 2026. From Intel's mass production and shipment of the world's first glass substrate processor, Clearwater Forest, to TSMC's aggressive push for CoWoS glass process production line construction, and the simultaneous launch of Samsung and Absolics' glass substrate mass production factory construction, the entire industry is advancing a brand-new technology—glass substrates.
At the recently concluded ECTC 2026 conference, Corning presented its latest paper, "Low-Loss Optical Interconnect Designs in Optimized Glass for Co-Packaged Optics." ECTC is the main battlefield for advanced packaging. Corning's two core R&D teams, located at its US headquarters and in Berlin, Germany (with Lars Brusberg as the first author of the paper), have gone all-in on glass materials. While the core of the paper on the surface discusses the strong performance and lower loss of glass substrate optical waveguides, the actual core is the glass formulation. During full-power operation of computing chips in CPO packaging, the temperature in the adjacent area can reach as high as 110°C. This temperature causes the silver ions in traditional ion exchange (IOX) glass to continuously diffuse, leading to a decrease in the refractive index and an expansion of the mode field, ultimately causing failure and significantly reducing device reliability. Corning's new glass substrate solution perfectly solves this problem.
Corning's solution places both optical and electrical signals on the same glass substrate: first, optical waveguides are created in the glass using ion exchange, and then thin-film circuits are fabricated in the etched grooves. The PIC is coupled to the glass substrate via flip-chip evanescent field coupling, and then connected to the RDL layer using microbumps. This architecture, which adopts millimeter-scale co-packaged optics on glass substrates and utilizes panel-scale manufacturing processes.
The industry has condensed the core of this paper into a single question: How can we mass-produce a platform that can operate continuously for five years without performance degradation in an 110°C high-temperature environment, while also achieving low coupling loss and an ultra-small size optical waveguide platform? The entire industry has been struggling with the material challenge of simultaneously achieving small size, low loss, thermal reliability, and mass production, but Corning has achieved it. The paper compares the refractive index △n and lifespan (under the condition of a 110°C high-temperature environment) of Corning's specially formulated glass for CPO packaging and commercially available optical waveguide glass. The conclusion is very clear: ordinary glass is basically unusable after three months, while the specially formulated glass for CPO sees less than 1.5% change in refractive index even after five years.
Global Supply Chain Integration: How Far Is the Road to Mass Production? Given the heat surrounding glass substrates, the upstream and downstream industries are also beginning to stir. Glass itself is an insulator; optical signals can pass directly through it, while electrical signals require the TGV (Through Glass Via) process, which involves drilling high-aspect-ratio vias in the glass and filling them with conductive metal to form electrical signal pathways. The entire supply chain is focusing heavily on yield, cost, and aspect ratio (via density). Looking at the TGV industry, there are four mainstream processes:
- Physical drilling and sandblasting: Achieves a minimum hole diameter of about 180um and an aspect ratio of less than 5:1 using ultra-fine drill bits made of superhard alloys. However, due to severe edge chipping, it is currently hitting a bottleneck. Sandblasting, on the other hand, results in uneven hole diameters and fails to meet aspect ratio requirements, making it nearly obsolete.
- Laser ablation: Can achieve hole diameters of about 30-40um and an aspect ratio of 10:1. However, laser ablation leaves a recast layer and a micro-crack layer on the glass, affecting the quality of subsequent metal filling.
- Laser Induced Deep Etching (LIDE): Modifies the interior of the glass hole using ultra-short pulse lasers and then etches it with an acidic solution. It can achieve hole diameters of <10um and an aspect ratio of >50:1. With high efficiency in mass production batch processing, it is highly favored by the industry.
- Special photosensitive materials: Specially formulated photosensitive glass is exposed to UV to define the hole areas, followed by heat treatment and selective etching using a dilute acidic solution. It can achieve hole diameters of 25um and an aspect ratio of 20:1. However, it requires special materials and has a narrow range of applications.
The Laser Induced Deep Etching (LIDE) process is currently recognized as the optimal route and is the solution being advanced by leading players such as Intel. Once the through-holes are etched, metallization filling and RDL processes are required. Void-free copper filling of these high-aspect-ratio vias, followed by routing to create a redistribution layer bonded to the microbumps of EIC and PIC, directly determines the quality of electrical connections on the glass substrate.
Corning's glass substrate has advanced optical waveguides from laboratory verification to process integration verification. When electrical (TGV) and optical (IOX waveguides) components can be fabricated simultaneously on the same piece of glass, glass material suppliers, panel-level process providers, equipment and testing companies, and advanced packaging houses all stand to benefit from this supply chain. The three glass industry giants—Corning, Schott, and AGC—will capture the vast majority of the global market share. In particular, Corning is currently shipping advanced packaging temporary carriers and DRAM ultra-thin carriers in mass production, and glass substrates are being sent to the majority of CPO manufacturers for sample verification. On the equipment side, laser processing equipment and copper electroplating equipment are the two core pieces of equipment. On the panel manufacturing side, panel manufacturers such as BOE and Woge Optoelectronics have the capability to transfer panel processes to glass substrate processing. For the glass substrate supply chain, its value will not just remain in the material itself but will diffuse layer by layer along the path of "glass materials—TGV processing—metallization electroplating—RDL/Build-up—CMP planarization—inspection and metrology—packaging and testing".
Conclusion As the new foundation for AI advanced packaging, the glass substrate supply chain is moving from "proof of concept" to "mass production verification." On the surface, the competition in computing clusters is a competition among GPUs, HBM, and CPO, but in essence, it is a competition of the underlying materials and process platforms for advanced packaging. The race for glass substrates to replace organic substrates will kick off in 2026.
References: "ECTC 2026 | Corning | Low-Loss Optical Interconnect Designs in Optimized Glass for Co-Packaged Optics" - STT Knowledge Planet: Global Tech Stock Investment "Glass Substrates Are No Longer PPT Technology: Why the TGV Track Will Be Fully Realized in 2026"
