Influence of non-confined electrons at the boundaries in a HPPMS discharge - limit to Gyro-average validity

Sara Gallian, Denis Eremin, Thomas Mussenbrock, Ralf Peter Brinkmann

ICOPS 2012, Edinburgh, UK, July 8-12.


High Power Pulsed Magnetron Sputtering (HPPMS) is a novel Ionized Physical Vapor Deposition (IPVD) technique, able to achieve an ultra dense plasma with a high ionization degree of sputtered atoms.\ In most HPPMS configurations the following ordering of quantities holds: $lambda_{text{D}} ll s_text{t} ll r_text{L} ll L text{ and } omega_{text{pe}} gg omega_{text{ce}} gg nu_{text{ce}}$, where $lambda_{text{D}}$ is the Debye length, $s_{text{t}}$ is the sheath thickness, $r_{text{L}}$ is the Larmor radius, $L$ is the system characteristic length, $omega_{text{pe}}$ is the electron plasma frequency, $omega_{text{ce}}$ is the electron cyclotron frequency and $ nu_{text{ce}}$ is the electron collision frequency. Thus, outside the sheath region the electron gyromotion lives on a spatial and temporal scale much smaller than all other phenomena, and one can describe the electron dynamics with gyro-averaged equations of motion. In a magnetron, most of the electrons are confined by the magnetic field, and they bounce along the magnetic field lines, but some of them enter the loss cone region and get reflected inside the sheath or reach the target surface. However, due to the high target negative bias, the latter group can safely be neglected.\ We show that electrons reflected by the sheath, assumed infinitely thin, present an average drift in the plane of the target, an effect that can potentially influence the magnetron performance. We investigate here the statistical importance of this group of electrons by single particle simulation in different magnetic field configurations.

Docutils System Messages

System Message: ERROR/3 (<string>, line 1); backlink

Unknown target name: "s".

System Message: ERROR/3 (<string>, line 1); backlink

Unknown target name: "r".

Tags: confinement-boundaries, HPPMS-magnetic