Modelling of the cathode sheath region of magnetron discharges

Summary form only given. This paper describes the results of a numerical model of the cathode sheath region near the target of a magnetron discharge, operating with a magnetic field of a few hundred Gauss and at a few millitorr pressure of argon. Under these conditions, the gyro-radii of the electrons emerging from the cathode into the electric-magnetic potential well are typically of the same order or smaller than the width of the positive space charge computed from the Langmuir-Childs law. Inclusion of the electron density in the solution to Poisson´s equation gives a first order correction to the sheath width resulting from the enhanced electron confinement. If the electrons motion is approximated using a fluid model, with constant electron current density in the sheath, it is found that the influence on the sheath is strongly dependent on the model for electron mobility across magnetic field lines. If mobility were classical, calculations show that the sheath width would increase with increasing magnetic field. If electron mobility is assumed to follow the Bohm law, the sheath width is independent of the magnetic field and assumes the Langmuir-Childs condition. The effect of ionization of argon in the sheath region is included.