Nonlinear multiphoton modification of glass substrates for fabrication of high aspect ratio through-glass vias

To meet the demands of high-frequency wireless communications and Internet of Things (IoT) applications, modern integrated circuit (IC) packages should support operating frequencies in the GHz range and be implemented on fine substrate structures. Glass has many advantages as an interposer material for three-dimensional IC (3D-IC) designs, including tunable electrical and mechanical properties, amenability to large-scale processing, and high optical transparency in the visible range. Moreover, glass is easily processed to produce the through-glass vias (TGVs) required to realize high-frequency circuit designs and microelectromechanical systems devices. The present study proposes a method for patterning TGVs on glass substrates via a nonlinear multiphoton-assisted modification process performed using single-pulse irradiation by a 1030-nm picosecond laser. A theoretical model is additionally proposed to describe the glass substrate modification mechanism induced by the nonlinear multiphoton excitation effect. The feasibility of the proposed method is demonstrated by patterning a TGV array with a high aspect ratio of 1:10 and a taper angle of ∼2° on a Corning SGW3 glass substrate.