DEPOSITION RATES IN DIRECT-CURRENT DIODE SPUTTERING

A physical model for anode deposition rates in parallel-plate, dc-diod e sputtering is presented and tested. The deposition rate has been mea sured as a function of the discharge voltage, the anode-cathode gap an d the pressure, using silicon or molybdenum cathodes with argon. Depos ition rates as high as 23 angstrom/s were obtained using 3 kV, and it is shown that deposition efficiency is similar to that obtained with m agnetrons. The deposition rate varies inversely with anode-cathode gap at constant pressure and voltage and almost linearly with power densi ty for discharge voltages above a threshold which depends on the catho de material. These observations are explained by the model, which can be used to estimate the deposition rates for any cathode material and gas for which the ion sputtering yields are known. Potential advantage s and complications of dc diode sputtering for thin film deposition ar e discussed, and optimum conditions for high, uniform deposition rates are described.