A device includes an inter-layer dielectric, a device die under the inter-layer dielectric; and a die-attach film under the inter-layer dielectric and over the device die, wherein the die-attach film is attached to the device die. A plurality of redistribution lines includes portions level with the die-attach film. A plurality of Z-interconnects is electronically coupled to the device die and the plurality of redistribution lines. A polymer-comprising material is under the inter-layer dielectric. The device die, the die-attach film, and the plurality of Z-interconnects are disposed in the polymer-comprising material.