Demonstration of Deep-Hole Drilling for Next-Gen Semiconductor Packaging Glass Core Substrates Without Special Optical Systems

Symphotony has successfully demonstrated drilling technology on transparent materials such as glass using its ultra-precision femtosecond laser processing machine, 'Femto-pro'. This achievement aims for application in glass core substrate processing for next-generation semiconductor packaging.

In recent years, the advancement of AI semiconductors and HPC (High Performance Computing) has driven the evolution of advanced packaging technology using chiplet structures. Consequently, glass core substrates are gaining attention as an alternative material to traditional organic substrates and silicon interposers.

Glass core substrates possess characteristics suitable for high-frequency signal transmission, in addition to high insulation, low thermal expansion, and excellent flatness, making them highly anticipated for large-scale, high-density packaging applications.

In the practical application of glass core substrates, TGV (Through Glass Via) formation technology is crucial. TGV is the technology for forming vias to electrically connect the front and back of the glass core substrate, and processing quality and mass productivity significantly impact package performance. Conventional TGV formation often involves complex processes combining laser modification and etching, leading to challenges such as process complexity, equipment costs, and quality variability.

To address these issues, the company conducted this technical demonstration to verify the potential of a simpler and more direct laser glass drilling process.

[Technical Overview]
This processing was realized by leveraging the company's proprietary 'GHz Pulse Injection Technology' in a femtosecond laser. By injecting a high-repetition pulse train in the GHz band into the transparent material at high density, stable energy application was made possible.

Another feature is that it realizes processing with a simple optical configuration, without using special optical systems such as Bessel beams typically used in conventional internal transparent material processing. This is expected to simplify equipment configuration and enhance potential application to mass production equipment.

[Processing Examples]
The following results have been confirmed through this technical demonstration:
- 4 mm depth drilling on 15 mm thick crown glass
- Through-hole processing on 1.2 mm thick soda glass (Back-side hole diameter: 5 μm, Aspect ratio: 240)

With this, the effectiveness of this method was confirmed for both deep-hole and through-hole processing on glass materials. This result is positioned as basic validation for TGV formation with high aspect ratios and glass core substrate processing.

[Equipment Overview]
The processing used the company's ultra-precision femtosecond laser processing machine, 'Femto-pro'. Femto-pro is a platform equipped with a femtosecond laser light source capable of producing three-wavelength ultra-short pulse lasers and a precision processing stage. It allows flexible setting of processing conditions according to material characteristics. It covers a wide range of applications from R&D to processing verification of semiconductor-related materials.

[Features of this Processing]
The main features of this processing case are as follows:
- Demonstration of deep-hole drilling on glass materials for TGV formation
- Simple configuration without special optical systems such as Bessel beams
- Internal material processing using GHz Pulse Injection Technology
- Simplified equipment configuration with a view to mass production processes

The company offers proposals and technical consultations for various laser processing machines. They provide support for examining processing methods tailored to applications, including glass material processing for semiconductor packaging and laser application to difficult-to-process materials.