Plasma Chemical View of Magnetron and Reactive Ion Etching of Si with Cl2

Abstract

Magnetron reactive ion etching and conventional reactive ion etching of Si with Cl₂have been investigated in the light of the corresponding plasma properties of the discharges. Experiments were performed over a wide pressure range using a planar 13.56-MHz rf plasma reactor, with and without an external magnetic field parallel to the cathode surface. Plasma diagnostics included microwave interferometry, mass spectrometry, optical emission spectroscopy, and laser-induced fluorescence. Attention was focused on ion energies and fluxes onto the cathode and neutral radical densities in the plasma, which are related to the etching characteristics obtained. The outstanding plasma features observed are that in magnetron, the plasma density and hence the ion flux to the surface are about an order of magnitude higher, but the flux of neutral radicals is reduced relative to ions.