Impact of alkaline earth oxides on dielectric properties of photoetchable glasses as interposers for integrated circuits packaging

Abstract

Photoetchable glasses (PEGs) are widely used in integrated circuits as interposers. However, the high dielectric losses intrinsic of PEGs limit their applications in three-dimensional system packaging. Doping with alkaline earth oxides changes the network structure of the PEG, restricting migration of cations, and reducing structural and conduction losses in the glass. After UV exposure and annealing, the dielectric constant and dielectric loss decreases to 4.1 and 0.0025, respectively. Doping with alkaline earth oxides does not significantly decrease the glass transition temperature or viscous flow properties and thus the preferred use of PEGs as interposers. The breakdown filed strength of PEGs can reach 112 kV/cm, which increases their utility and range of applications. Analyses by X-ray diffraction and Raman spectroscopy reveal that alkaline earth oxides form polyhedra resulting in more complex glass networks. A small number of alkaline earth oxides can reduce their dielectric loss. Overall, the introduction of alkaline earth oxides improves their dielectric properties and breakdown filed strength, making PEGs more suitable as VLSI interposers.