Effect of Al2O3 on structural dynamics and dielectric properties of lithium metasilicate photoetchable glasses as an interposer technology for microwave integrated circuits

Abstract

Photoetchable glasses (PEG) are widely used as interposers in radio frequency electronic systems. However, high dielectric losses limit the utilization of PEGs in three-dimensional integrated microsystems. Herein, the internal structure of PEGs is shown to be altered by the addition of Al2O3 and its influence on dielectric properties systematically studied by X-ray diffraction, Raman spectroscopy and FT-infrared spectroscopy (FTIR). The Al2O3 content significantly influences the ring structure and an amount equal to 4 wt% results in a high degree of crystallinity and phase purity of lithium metasilicate. Lastly, a dielectric constant of 5.1 and dielectric loss of 3 × 10-3 were obtained at 1 GHz, which is attributed to weakened structural vibrations, without loss to attractive etching properties.