In one embodiment, an integrated circuit package substrate includes a core layer comprising a dielectric material and a plurality of metal vias within the core layer. The dielectric material includes Silicon, Oxygen, and at least one of Boron or Phosphorus. The metal vias electrically couple a first side of the core layer and a second side of the core layer opposite the first side. The package substrate further includes a plurality of build-up layers on the core layer, the build-up layers comprising metal vias electrically connected to the metal vias of the core layer.