A foundation layer having a stiffener and methods of forming a stiffener are described. One or more dies are formed over the foundation layer. Each die has a front side surface that is electrically coupled to the foundation layer and a back side surface that is opposite from the front side surface. A stiffening layer (or a stiffener) is formed on the back side surface of at least one of the dies. The stiffening layer may be directly coupled to the back side surface of the one or more dies without an adhesive layer. The stiffening layer may include one or more materials, including at least one of a metal, a metal alloy, and a ceramic. The stiffening layer may be formed to reduce warpage based on the foundation layer and the dies. The one or more materials of the stiffening layer can be formed using a cold spray.