Substrate Heating in Sputter Processes

Based on data from Langmuir probe and optical emission spectroscopy (OES) measurements the contributions of different substrate heating mechanisms to the total heat flux are discussed for two sputter processes, gas flow sputtering (GFS) and magnetron sputtering. The variation of these contributions with deposition parameters shows ways to reduce the heat flux to the substrate. In the GFS process the ratio of deposition rate to heat flux could be greatly increased by a proper choice of process parameters, notably process pressure. The main contribution to substrate heating in a typical GFS process results from the recombination of electron-ion-pairs and convection heating by the hot process gas. In unbalanced magnetron sputtering of heavy target atoms most of the heat input into the substrate surface comes from reflected, energetic neutrals and high energy electrons.