ELECTRICAL-PROPERTIES OF RF SPUTTERING SYSTEMS

A theory is developed that gives a relatively complete electrical characterization of rf sputtering systems. Three types of systems areanalyzed: tuned substrate, driven substrate, and controlled area ratio of electrode (CARE) systems. The theory is applicable to any of these systems that do not use magnetic fields to confine the plasma. Given the input rf power and voltage at the target, and any other parameters that can be specified as independent variables. The theory provides explicit values for all dc and rf electrical parameters of system. The dc bias developed at the substrate is explained and related to the resputtering energy. In addition, an approximate calculation is presented for the ion density in the plasma; this calculation allows a semiquantitative estimate of the rf voltage developed at the target for a given value of rf input power. It also shows the influence of pressure and frequency on rf sputtering system operation.