Magnetically enhanced plasma reactor system for semiconductor processing

摘要

Magnetic confinement of electrons in a plasma reactor is effected using electro-magnetic coils and other magnets which generate respective magnetic fields which are mutually opposed and substantially orthogonal on their common axis to the major plane of a wafer being processed, instead of being aligned and parallel to the major plane as in prior magnetically enhanced plasma reactors. The respective magnetic fields combine to yield a net magnetic field which is nearly parallel to the wafer away from the magnetic axis so that electrons are confined in the usual manner. In addition, a magnetic mirror provides confinement near the magnetic axis. The ExB cross product defines a circumferential drift velocity urging electrons about a closed path about the magnetic axis. The magnetic and cross-product forces on plasma electrons have a rotational symmetry which enhances reaction uniformity across the wafer; this contrasts with the prior art in which lateral drift velocity disturbs plasma symmetry and thus reaction uniformity. Furthermore, the disclosed field geometry permits stronger electron confinement which enhances plasma reaction rates.