Laser-induced and room temperature etching of copper films by chlorine with analysis by Raman spectroscopy

The reactions of copper films on glass with chlorine are studied at room temperature with and without a focused laser (4880 Å) present for localized heating. Raman scattering is used to follow the transformation of the copper film in situ to the copper chlorides, CuCl and CuCl2. At room temperature, a thin film forms on top of partially passivated copper with chlorine present, which is identified to be CuCl by Raman spectroscopy at 77 K. This copper chloride film is locally desorbed by laser heating in vacuum. Deposition-like features are produced on passivated Cu films and CuCl-on-Cu films by laser heating with Cl2 present. Raman spectroscopy shows that these features are CuCl2, with CuCl sometimes also present. After the copper chloride is removed, ∼4 μm wide etched features remain in the copper film. The Raman spectrum of anhydrous CuCl2 presented here is apparently the first such measurement.