Excimer Laser Photochemical Directional Etching of Phosphorous Doped Poly-Crystalline Silicon

Photochemical anisotropic etching of a gate material for MOS devices ( n + poly-Si) has been investigated, based on the Reactive Ion Etching (RIE) mechanism. By adding deposition gas to the etching gas (chlorine), a thin organic film can be formed for preventing chlorine atoms from reacting on the sidewalls of fine patterns. Simultaneously, a normally irradiated laser beam removes the film at the bottom surface and promotes an etching reaction. Thus, directional etched features can be achieved. Also, radiation damage can be evaluated in comparison with RIE. The photochemical etching technique is one of most suitable processes for future MOS devices without radiation damage.