Coaxial microwave applicator for an electron cyclotron resonance plasma

Abstract

A method and apparatus are disclosed employing a microwave applicator for use with an electron cyclotron resonance (ECR) plasma source for applications including, but not limited to, etching and chemical vapor deposition. A magnetic field is generated by magnets circumferentially arranged about a chamber that is symmetrical about its longitudinal axis. The microwave applicator, which comprises one or more pairs of slotted antenna arrays, injects and distributes microwave power about the entire periphery of a plasma forming portion of the chamber. The antenna arrays include a plurality of radiating stubs for radiating microwave power. The stubs are positioned along the arrays at predetermined intervals for efficiently distributing microwave power uniformly about the periphery of the plasma forming portion. The position and orientation of the radiating stubs cause microwave power to be launched into the plasma in the form of propagating waves with a polarization suitable of electron cyclotron heating. The applicator is coupled to a microwave power source that preferably supplies microwave power at a frequency of 2.45 GHz. A magnetic-field free region produces uniformity of plasma distribution in a plasma stream that approaches an outlet in the chamber. The plasma stream flows through the plasma forming region toward the specimen with characteristics of high density, uniformity over transverse dimensions larger than the specimen, and low plasma temperature, while operating at gas pressures which can be varied over a wide range.