Gas heating in plasma-assisted sputter deposition

We present a theoretical framework to deal with an important source of nonhomogeneity in plasma-assisted sputter deposition. The gas heating due to the interaction between the background gas and the flow of energetic sputtered particles seems to be of significance under realistic deposition conditions. The results illustrate that the decrease of the gas density due to this heating has to be taken into account for a proper description of the deposition process, even when the total pressure in the system remains constant. The Keller-Simmons equation, that describes the deposition rate in a parallel plate reactor, has been studied in the case of such a nonhomogeneous plasma. We determine the conditions for its applicability and find a direct relation between the throw distance, the temperature of the growing film and the cross section of elastic scattering of a sputtered atom on a gas particle. (C) 2005 American Institute of Physics.