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

Abstract

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 Å/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.

Kinetic-energy measurement of a neutral stream extracted from Ar electron cyclotron resonance plasma

“…Recently, we showed that charged particles could be eliminated by using a magnetic field and succeeded in extracting only the neutral species. 13,14 We used the extracted energetic neutral species, which we call a ''neutral stream,'' for Si etching. We found that neutral stream etching with Cl 2 and SF 6 provided anisotropic etching profiles.…”

Effect of surface roughness of the neutralization grid on the energy and flux of fast neutrals and residual ions extracted from a neutral beam source

“…This so-called neutral beam etching ͑NBE͒ has been the subject of continuing research. [6][7][8][9][10][11][12] To make NBE practical on an industrial scale, the energy and flux of the fast neutrals need to be comparable to those of ions in reactive ion etching. To obtain a high flux of fast neutrals, Panda et al 13 and Samukawa et al [14][15][16] have used high density inductively coupled plasmas ͑ICP͒.…”

Plasma Acceleration by Area Expansion

“…We assume the ionization is caused by electron impact ionization and neglect recombination. Thus S = ß(T e )nN = co(T e )n (3) where N is the background neutral density, and ß is the average of the ionization cross section times the electron velocity. The force equation comes from taking the total momentum equation (electron plus ion, but neglecting electron inertia) and subtracting u times the density equation.…”

“…The two applications which we have in mind are plasma processing with a stream of neutrals [3,4], and space propulsion (i.e. a plasma thruster) [5].…”