Disclosed herein are cavity structures in integrated circuit (IC) package supports, as well as related methods and apparatuses. For example, in some embodiments, an IC package support may include: a cavity in a dielectric material, wherein the cavity has a bottom and sidewalls; conductive contacts at the bottom of the cavity, wherein the conductive contacts include a first material; a first peripheral material outside the cavity, wherein the first peripheral material is at the sidewalls of the cavity and proximate to the bottom of the cavity, and the first peripheral material includes the first material; and a second peripheral material outside the cavity, wherein the second peripheral material is at the sidewalls of the cavity and on the first peripheral material, and the second peripheral material is different than the first peripheral material.