Plasma-chemical reactor with low ion energy for selective etching

Abstract

The results of physical and technological tests of the modernized plasma-chemical reactor are presented. The chemically active ion's energy may be controlled by the magnetic field intensity in the range from 15 eV to 100 eV. (If it is necessary the ion energy may be increased up to 300 eV). The current density is /spl les/l5 mA/cm/sup -2/. The samples for etching are attached to the top side of the three-edged prism that is an active reactor electrode. The side site is 110/spl times/130 sg mm. High stability and repeatability of its physical parameters characterize the reactor. A number of experiments have corroborated the selective etching of Si/sub 3/N/sub 4/ with respect to SiO/sub 2/, PSG with respect to Al etc. Different kinds of material such as silicon, polysilicon, titanium nitride, titanium, tungsten and molybdenum silicides are easily etched. The etching selectivity may be varied in a wide range by the gas nature, current density and ion energy variation. In fact the selective removing was realized on the layers having element size /spl plusmn/0.35 microns and the bottom metal interconnection layers were discovered. The dry and wet etching alternation assures a suitable surface quality of an analyzed layer even after a number (up to 20) top layers of multi-layer structure were removed.