Chemical vapor etching of copper using oxygen and 1,1,1,5,5,5-hexafluoro-2,4-pentanedione

The use of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hfacH) and oxygen to thermally dry etch copper was studied using a vertical flow reactor. The two primary reaction steps in this process are the oxidation of copper by oxygen to form copper(I) and copper(II) oxides and the subsequent removal of the oxide by reactions with hfacH to form copper(II) bis-hexafluoroacetylacetonate and water. Etch rates as high as 1.5 mu m at 350 degree C were achieved by the simultaneous flow of hfacH and oxygen. Etch rates and surface composition were found to be a function of temperature, reactant partial pressures, and surface morphology. At high hfacH to oxygen ratios the surface remained copper colored and the etch rate was nearly independent of the hfacH partial pressure but was more strongly dependent on the oxygen partial pressure and surface morphology. At low hfacH to oxygen ratio the surface became deep rose colored and the etch rate became nearly independent of the oxygen partial pressure and the surface morphology but had a strong dependence on the hfacH partial pressure. These results show that copper can be etched successfully by chemical vapor etching. However, more work needs to be done before this becomes a useful commercial process.