Magnetoplasmadynamic apparatus for the separation and deposition of materials

摘要

A plasma arc discharge method for deposition of metallic and semiconductor layers on a substrate for the purpose of producing semiconductor grade materials such as silicon at a reduced cost. Magnetic fields are used so that silicon ions and electrons can be directed toward a target area where they are deposited. The ions and electrons are preferably injected as a compound in gaseous of liquid form but may also be injected in liquid elemental form or vaporized from a thermionic cathode. The magnetic fields include an accelerating magnetic field and a focusing magnetic field. The accelerating magnetic field is adjusted to support a desired high ion flux rate and the focusing magnet can control the plasma beam direction and divergence. The silicon provided in a compound form or in the form of metallurigical silicon is purified during the deposition process by a carrier substance which may be a part of the compound or separately injected. Chemical purification is accomplished by separation of the silicon due to ionization potential differences between silicon and other elements. The magnetic acceleration technique allows the use of pressures under 10-1 torr thereby facilitating plasma formation and allowing the materials to be deposited with a desired high purity.