Generation of Electron Cyclotron Resonance Neutral Stream and Its Application to Si Etching

A low-energy (10–20 eV) neutral stream generated by charge exchange reactions in an electron cyclotron resonance (ECR) plasma stream is extracted by eliminating charged particles and used for Si etching. The formation of a cusp magnetic field over the substrate eliminates charged particles because electrons are led outside the substrate by the magnetic field. In addition, residual ions are repelled by a positive voltage supplied to the substrate, and it becomes possible to irradiate the etching samples with only the neutral stream. The etch rate for Si is about 100 A/min with a gaseous mixture of Cl2 and a small amount of SF6, and a microwave power of 400 W. We confirm that neutral stream etching allows us to attain anisotropic etching shapes without distortion, and that it can be used for delineating fine patterns.