Through Glass Via Drilling Using GHz-bursts of Femtosecond Pulses: Challenges and Implementation

Femtosecond GHz-burst mode laser processing is very appropriate for top-down percussion drilling of blind holes in glasses with very high aspect ratio and outstanding hole quality.There is a big interest in drilling through glass vias for applications in microelectronics.However, our study in GHzburst mode reveals certain constraints and limits in through glass via drilling concerning the outlet diameter of the holes at the rear surface, which is systematically smaller than expected from the results obtained for blind holes.In order to study this observation for different sample thicknesses, we prepared bevel samples and performed light transmission measurements.Finally, we demonstrate how to overcome these limits and suggest an implementation strategy.These results might be of significant importance for industrial applications of through glass via drilling in GHz-burst mode.