Heated Langmuir probe measurements of reactive direct‐current magnetron plasmas

A modified Langmuir probe has been used to study the plasma produced during dc reactive sputtering of AlN. The probe element was heated during the measurements to prevent the accumulation of an insulating layer of AlN. Ion and electron densities and electron energies have been determined as functions of cathode power, total pressure, and Ar:N₂ partial pressure ratio. The electron densities increased as both cathode power and total pressure were increased, and decreased as the nitrogen content in the plasma was increased. Electron energies increased as cathode power was increased and total pressure was decreased and a strong interaction between partial pressure ratio and total pressure was observed. This interaction is understood as a result of changes in both the target voltage and the total collision cross section for electrons in the plasma as the nitrogen partial pressure increases.