Through-Glass Via (TGV): Future-Ready Packaging for RF and Photonics
Introduction
With the rapid evolution of semiconductor technology, the demand for high-performance, miniaturized, and heterogeneous integration continues to accelerate. Packaging solutions must evolve to support higher frequencies, greater component density, and novel functionalities such as photonics and MEMS. One technology at the forefront of this evolution is Through-Glass Via (TGV)—a vertical interconnection method utilizing glass substrates to create highly reliable, low-loss electrical pathways through the package.
Unlike conventional Through-Silicon Via (TSV) or organic PCB-based approaches, TGV leverages the unique electrical, thermal, and mechanical properties of glass, making it particularly suitable for next-generation 5G, millimeter-wave (mmWave) communications, automotive radar, and optical systems.
What Is Through-Glass Via (TGV)?
Through-Glass Via (TGV) is a vertical interconnect fabricated by drilling or etching vias through a glass substrate and filling these vias with conductive metals, typically copper. These metalized vias create vertical electrical connections between the front and back sides of the substrate, enabling three-dimensional (3D) integration and system-level packaging.
The glass substrate acts as an insulating medium with low dielectric constant and low RF loss, which significantly improves signal integrity in high-frequency applications.
Advantages of TGV over TSV and Traditional Packaging
| Feature | TGV (Glass) | TSV (Silicon) | PCB (Organic) |
|---|---|---|---|
| Dielectric Constant (Dk) | 3.8–5.5 (low) | ~11.7 (high) | ~4.5 (medium) |
| RF Signal Loss | Very low | Moderate | High |
| Electrical Insulation | Excellent (intrinsic) | Requires liner layer | Moderate |
| Thermal Expansion (CTE) | Tunable, low mismatch | Silicon matched | Often mismatched |
| Transparency | Optical transparency | Opaque | Opaque |
| Mechanical Stability | High | Moderate | Low |
| Cost | Medium | High | Low |
These advantages enable TGV substrates to support high-frequency, low-loss RF signals, high-density interconnects, and optical integration—features essential for emerging applications such as 5G wireless modules, LiDAR sensors, and AR/VR devices.
Detailed Fabrication Process of TGV
1. Glass Substrate Preparation
Typical glass materials used include borosilicate glass, fused silica, and aluminosilicate glass. The substrates are often ultra-thin, ranging from 100 to 500 microns, balancing mechanical strength and miniaturization needs.
2. Via Formation
- Laser Drilling: Ultrafast lasers create vias with diameters from 10 to 100 microns.
- Plasma Etching: Offers high precision and smoother via walls for dense interconnects.
- Wet Chemical Etching: More cost-effective but requires precise process control.
3. Via Wall Insulation (Optional)
While glass is an insulator, sometimes additional thin films such as SiO₂ or SiNx are deposited to improve reliability and prevent metal diffusion.
4. Seed Layer Deposition
A conductive seed layer (usually Ti/Cu) is deposited on the via walls by sputtering or evaporation to enable subsequent metal electroplating.
5. Copper Electroplating and Via Filling
Copper is electroplated to fill vias, creating low-resistance conductive paths. Uniform deposition and void-free filling are critical for electrical reliability.
6. Surface Planarization (CMP)
Chemical Mechanical Polishing (CMP) smooths the substrate surface and removes excess copper to ensure compatibility with further processing.
7. Redistribution and Integration
Additional metallization layers, passives, or microelectronic components are added. The TGV substrate can then be integrated with chips or other substrates through wafer-level bonding or system-level packaging.
Key Applications of TGV in Semiconductor Packaging
1. RF Front-End Modules (FEM)
The rise of 5G and mmWave communications demands packaging with low insertion loss, high isolation, and thermal stability. TGV substrates meet these requirements better than organic PCBs or silicon-based interposers, improving power amplifier and antenna performance.
2. Photonics and Optical Devices
Due to the glass substrate’s optical transparency, TGV technology supports VCSEL arrays, photodetectors, and on-glass optical waveguides, enabling advanced integrated photonics platforms for data communications and sensing.
3. MEMS Packaging
For sensors like accelerometers, gyroscopes, and pressure sensors, TGV enables compact packaging with excellent insulation and mechanical robustness.
4. System-in-Package (SiP) and 3D Integration
Glass interposers with TGV provide a platform for multi-die integration with reduced crosstalk and improved signal fidelity, critical for heterogeneous integration trends.
Industry Trends and Market Outlook
- Panel-Level Packaging (PLP): The semiconductor industry is moving from wafer-level to panel-level manufacturing to reduce costs. Glass substrates used in TGV processes offer the dimensional stability required for large panels.
- Increasing Demand in 5G and Automotive Radar: TGV’s superior high-frequency performance drives its adoption in mmWave antenna-in-package (AiP) modules for smartphones and automotive LIDAR systems.
- Expansion in Photonics: The push for silicon photonics and optical interconnects encourages integration of TGV-based transparent substrates.
- Leading Players: Industry leaders such as 3D Glass Solutions, Corning, Schott, and ASE Technology are actively developing TGV technologies and solutions.
Challenges and Development Directions
While TGV technology offers many benefits, it faces challenges such as:
- Maintaining high via density and fine pitch for complex integration.
- Ensuring mechanical reliability and controlling warpage in ultra-thin glass.
- Achieving void-free copper filling to prevent electrical failures.
- Scaling manufacturing processes to achieve cost-effective mass production.
Future developments include thinner glass substrates (<100 μm), integration with Fan-Out Wafer-Level Packaging (FOWLP), and hybrid integration combining glass, silicon, and organic substrates.
Why SIMVACO is Your Trusted Partner for TGV Manufacturing Equipment
At SIMVACO, we understand the complexities and precision demands of TGV manufacturing. We specialize in providing high-performance vacuum coating and deposition equipment that are vital for every stage of the TGV fabrication process:
- Advanced Magnetron Sputtering Systems: For uniform seed layer and barrier film deposition on glass substrates.
- PECVD Equipment: For high-quality dielectric layer deposition ensuring via insulation and surface passivation.
- Inline Coating Solutions: Optimized for panel-level processing to increase throughput and maintain coating uniformity.
- Customized Equipment Solutions: Tailored to meet your specific TGV process parameters and integration needs.
With over a decade of experience in thin film vacuum technology and advanced coating systems, SIMVACO empowers manufacturers to produce reliable, high-performance TGV substrates, driving innovation in 5G, photonics, MEMS, and SiP markets worldwide.
Contact SIMVACO
Discover how SIMVACO can accelerate your TGV manufacturing capabilities.
🌐 Website: https://simvaco.com
📧 Email: simon@simvaco.com
Conclusion
Through-Glass Via (TGV) technology represents a transformative advancement in semiconductor packaging, enabling superior electrical performance, miniaturization, and integration possibilities beyond traditional TSV or organic PCB methods. As industries push toward 5G, photonics, and compact MEMS devices, TGV provides an ideal substrate platform combining low-loss electrical interconnects with optical transparency and mechanical robustness.
With SIMVACO’s industry-leading vacuum coating and deposition solutions, manufacturers are equipped to meet the technical challenges of TGV fabrication and capitalize on the growing demand for high-frequency, high-density packaging solutions.