Glass substrates, capable of supporting optical waveguide circuits on their surface, enable high-density integration of photonic-electronic co-packaging and are poised to become a key technological pathway for 102.4 Tbps and higher bandwidth Co-Packaged Optics applications. Industry players are actively deploying glass substrate processes, signaling the countdown to its industrialization. Through Glass Via technology is a critical process for glass substrate fabrication, involving steps such as laser drilling, metal filling, and high-density wiring. Attention is drawn to the demand for laser equipment required for high-aspect-ratio glass microvia processing and other process stages. The main viewpoints from Gf Securities are outlined below.

Glass Substrate Advantages and Future Prospects

Compared to traditional silicon and organic materials, glass offers advantages including a low coefficient of thermal expansion, high mechanical strength, excellent electrical isolation, and low high-frequency signal loss. It has already emerged as a significant development direction within the advanced packaging materials system, with its downstream application scenarios expanding from new display technologies to semiconductor advanced packaging and optical communications. In the field of advanced packaging, the introduction of glass material can replace the original silicon interposer and organic substrate. When combined with panel-level packaging processes, it can significantly improve wafer utilization while enhancing the substrate's transmission speed and bandwidth density. In optical communications, based on research team results presented by Corning at the 2025 IEEE 75th Electronic Components and Technology Conference, glass substrates can facilitate the preparation of optical waveguide circuits on their surface. This enables high-density integration of photonic-electronic co-packaging, positioning glass substrates as a potential key technological pathway for 102.4 Tbps and higher bandwidth Co-Packaged Optics applications.

Industry Momentum and Industrialization Timeline

The demand from AI for foundational performance and production capacity of computing chips is compelling major industry players to accelerate the industrial progress of glass substrates. For instance, Intel has achieved the initial manufacturing of large-layer, thick glass core substrates and simultaneously achieved the initial co-integration of optical waveguides. TSMC is actively advancing its CoPoS packaging technology, planning to replace silicon interposers with glass substrates. According to a Commercial Times report cited by the official public account of Chengdu Macro, equipment delivery for TSMC's CoPoS pilot production line commenced in February, with mass production expected to gradually roll out between 2028 and 2029. Furthermore, companies including Nvidia, Apple, Samsung, and LG are also deploying glass substrate processes, indicating that glass substrates have entered the countdown phase for industrialization.

Core Processes in TGV Fabrication

The processing of glass substrates involves steps such as drilling, filling, and RDL (Redistribution Layer) rewiring. Current challenges in TGV processing primarily focus on two aspects: the via formation process for TGVs and the high-quality filling of TGVs. (1) Via Formation: Creating high-quality glass vias with a high aspect ratio and narrow pitch is a core factor determining glass substrate performance. Currently, laser-induced etching is anticipated to become the mainstream process. (2) Via Filling: The smooth surface of glass material combined with poor adhesion of common metals necessitates methods such as bottom-up filling, butterfly filling, conformal filling, or via wall electroplating to achieve high-density via filling. (3) High-Density Wiring: Achieving high-density wiring on glass surfaces is more challenging than on organic or silicon materials. Processes such as Circuit Transfer Technology, Photosensitive Dielectric Embedding, and modified Semi-Additive Process are required to accomplish high-density wiring.

Potential risks include slower-than-expected progress in glass substrate process development, volatility in the semiconductor industry, and slower-than-anticipated growth in the advanced packaging market.