Discharge voltage measurements during magnetron sputtering

Abstract

The influence of different parameters on the discharge voltage, measured during planar magnetron sputtering, is studied for three different magnetron configurations. Using twelve different target materials, the influence of the material dependent ion-induced secondary electron emission (ISEE) coefficient is studied. An inversely proportional relation between the ISEE coefficient and the discharge voltage was found. Moreover, the discharge voltage increases with decreasing pressure, a behaviour which can be understood from the increasing recapture of electrons by the target. Furthermore, the influence of the magnetic field (target thickness) was investigated. A stronger magnetic field results in a better confinement of the electrons, resulting in a decrease of the discharge voltage at constant current.The current–voltage (I–V) characteristics of the three magnetron configurations was studied in a wide range of pressures and magnetic fields. The I–V characteristics are fitted to the relation I=β(V−V0)2. The value of β expresses the steepness of the I–V characteristic and its value depends strongly on the ISEE coefficients. Of special interest is the influence of the pressure on β: whereas at low magnetic fields β increases with increasing pressure, it decreases with increasing pressure at strong magnetic fields.