Abstract: A method of preparing a substrate for substrate bonding is provided. The method comprises: forming a recess in a substrate surface of the substrate, and forming a bondable dielectric layer on the substrate surface of the substrate. The bondable dielectric layer has a bonding surface on an opposite side of the bondable dielectric layer to the substrate surface, wherein the recess and the bondable dielectric layer define a dielectric cavity having a dielectric cavity volume. A plug is formed configured to make electrical contact to the substrate in the dielectric cavity volume. The plug has a plug volume which is less than the dielectric cavity volume, wherein the plug extends from the dielectric cavity beyond the bonding surface in a direction generally normal to the bonding surface. The plug is coined by compressing the substrate between opposing planar surfaces such that a contact surface of the plug is made co-planar with the bonding surface.