Chemical vapor cleaning of Si and SiO2 surfaces

A novel vapor phase clean is shown to be a viable method for removing copper and iron from wafer surfaces. Utilizing thin films and sub-monolayer samples of copper and iron on Si or SiO2 substrates the reaction of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (CF3COCH2COCF3 or H(+)hfac) with these metals has been explored as a potential vapor phase clean. It is shown that the chemical state of the surface metal is an important factor in the removal of these metals. The reaction of CuO and Cu2O with H(+)hfac results in volatile reaction by-products of Cu-II(hfac)(2) and H2O. Additionally, the reaction with Cu2O yields Cu-(0). Reaction of H(+)hfac with iron contamination is more complex and lends to at least two different types of reactions. These reactions include a nucleophilic substitution reaction and a reaction lending to a mixed ligand system. The final surface metal concentration is dependent upon the processing conditions and can result in concentrations similar to those achieved with standard wet cleans.