Aspects of the disclosure relate to forming a completed stack of layers. Forming the completed stack of layers may include forming a first stack of layers on a first substrate and forming a second stack of layers on a second substrate. The first stack of layers may be bonded to the second stack of layers. The first or second substrate may be removed. Prior to bonding the first stack of layers and the second stack of layer, one or more holes may be etched in the first stack of layers. After removing the second substrate, one or more holes may be etched in the second stack of layers, wherein each of the one or more holes in the second stack of layers extend into a corresponding hole in the one or more holes in the first stack of layers.