Etch the borosilicate glass to form a straight through-glass-via based on the FLACE technology

Abstract

Interposers will become more and more important for advanced electronic systems and through substrate vias are essential for the 3-D integration. A straight via is necessary because a tapered hole is accompanied by large signal loss. This article reports a straight through-glass-via (TGV) fabricated by femtosecond laser-assisted chemical etching (FLACE). The femtosecond laser was used to modify the glass substrates, and the modified glass samples were etched with hydrofluoric acid (HF) solution to form TGV. The effects of key processing parameters, including laser pulse energy, the number of burst pulses, and the HF solution concentration, on the TGV taper profile, were systematically investigated. It was found that the TGV taper sidewall angle increased decreased with increasing laser pulse energy and HF solution. And the number of bursts should be optimized because more than 10 bursts would prevent the formation of TGV. The study shows via etched in 3wt% HF after irradiation with 3 bursts of 60 μJ can become approximately vertical. Among the three processing parameters, HF concentration was found to be the most crucial parameter. This work can serve as a critical reference for applications of TGV in high-performance 3D integrated circuits.

Ultrahigh Aspect Ratio Through Glass Vias Perforation Utilizing Selective Laser‐Induced Etching with Nanochannels

“…Previous studies, including those by Xu et al [ 28 ] and Chen et al [ 29 ] have documented that the number of pulses in Bessel SLE impacts the taper angle in TGV fabrication. Specifically, when using borosilicate glass as the substrate, multipulse irradiation slightly increases the taper angle compared to single‐pulse irradiation, with increases recorded from 81.3° to 83.5°, and from 80° to 81°, respectively.…”

“…However, even though Bessel beams enable for more efficient processing, their processing performance is typically inferior to that of Gaussian beams. In the last two years of coverage, Xu et al [ 28 ] fabricated TGVs with a 4:1 aspect ratio, 60 μm diameter, and an 88.3° taper. Chen et al [ 29 ] fabricated TGVs with a 5:1 aspect ratio and 50 μm diameter.…”

Scanning strategy-dependent etching rate in the formation of through-via holes by femtosecond laser-assisted etching

“…25) Some studies have also reported that fabrication of TGVs by FLAE using Bessel beams (not focused beams). [26][27][28][29][30] In this case, laser modification can be performed quickly because no laser scanning is needed, but flexibility is lost.…”

A 3D coaxial transition with continuous ground wall fabricated by a 12-inch wafer-level packaging method for radio frequency applications

“…There are many vertical interconnection technologies in WLP, such as TSV and through-glass-via (TGV). However, these subtractive methods cannot realize continuous ground wall in the coaxial transition because the dielectric layer will drop out of wafer during the temporary bonding and de-bonding process (Braun et al , 2020; Motoyoshi, 2009; Guo et al , 2022; Xu et al , 2022b). Through-mold-via (TMV) is a similar method to TSV and TGV, always using subtractive manufacturing processes, such as laser drilling or imprint filling (Braun et al , 2011; Shibata et al , 2020), to fabricate vertical via.…”