Method of operation of electron cyclotron resonance plasma source

A method of generating plasma by electron cyclotron resonant (ECR) heating to treat specimens by processes including chemical vapor deposition and etching, comprising the steps of

• forming a cylindrical chamber which is symmetrical about its longitudinal axis,
• supporting one of the specimens adjacent one axial end of the cylindrical chamber,
• introducing a gaseous medium into the chamber,
• generating a circumferentially continuous and symmetrical magnetic field having lines of force forming continuous annular lobes also circumferentially extending about the chamber and continuous resonant interaction regions encircling the longitudinal axis of the chamber adjacent an opposite axial end thereof,
• developing a substantially field free region adjacent the one axial end of the chamber while minimizing the extension of magnetic field force lines into the magnetic field free region and toward the specimen,
• uniformly radiating electromagnetic radiation from a microwave power injector arranged between the magnet assemblies and having multiple injection axes extending radially inwardly toward the longitudinal axis of the chamber toward the resonant interaction region about the entire periphery of the chamber so that plasma electrons made energetic by interaction with the electromagnetic radiation are not permitted line of sight communication to the specimen along magnetic field force lines in the magnetic field free region, and
• maintaining low gas pressure in the chamber whereby a plasma stream flows through the magnetic field free region toward the specimen with characteristics of high plasma density, uniformity over transverse dimensions larger than the specimen, low plasma temperature and absence of energetic particles resulting from plasma instabilities even with operating gas pressures as low as 10.sup.-5 Torr.