Atomic-order layer-by-layer role-share etching of silicon nitride using an electron cyclotron resonance plasma

Atomic-order layer-by-layer etching of silicon nitride has been investigated using an ultraclean electron-cyclotron-resonance plasma. The surface nitrogen atoms in silicon nitride within only about one atomic layer from the surface were found to be removed selectively by excited hydrogen gas under well-controlled conditions. The remaining outermost silicon atoms were removed selectively by irradiation of a low-energy ${\mathrm{Ar}}^{\mathrm{+}}$ and ${\mathrm{H}}^{\mathrm{+}}$ ion mixture. By repeating these role-share cycles alternately, the resultant etching amount per cycle corresponded to one mean atomic layer of silicon nitride.