Ultrahigh-speed and high-aspect-ratio laser drilling of transparent materials through transient excitation (Invited Paper)

The integration of glass substrates in next-generation semiconductor devices is gaining attention owing to their excellent thermal, mechanical, and dielectric properties. However, the inherent hardness and brittleness of glass make it extremely difficult to machine with conventional techniques. Etching-based fabrication has become the dominant approach, but its multi-step complexity and environmental concerns limit scalability. Laser-based methods offer a more flexible alternative, yet traditional laser drilling requires several tens of seconds to fabricate a single micro through-hole with dimensions suitable for semiconductor applications (depth >1 mm, diameter <100 μm). To meet industrial demand— exceeding 1000 holes per second—innovative breakthroughs are required. In this work, we demonstrate an ultrafast glass drilling strategy that combines our previously developed Transient and Selective Laser (TSL) processing method with a Bessel beam configuration. A 5 ps Bessel-shaped pulse first induces a transient, highly excited electronic channel within the glass, which is subsequently and selectively absorbed by a microsecond Bessel pulse. This two-step interaction enables the formation of a 3 μm-diameter through-hole through 1 mm-thick glass in just 20 μs—approximately one million times faster than conventional techniques. Moreover, the hole diameter can be precisely tuned via processing duration. This method offers a promising route toward high-throughput manufacturing of glass-core and glass-interposer substrates for advanced semiconductor technologies.