Post metal etch polymer removal: A new CF4-based dry plasma process sequence

A novel CF4 based method for the dry plasma removal of post-metal etch polymer residues has been developed on a dual plasma source, dry cleaning system. This process eliminates the via damage problems observed when the traditional wet solvent clean process is used on specific embedded flash devices. In order to effectively clean these products, it was found that the CF4/O2/N2/H2 MW and RF dry plasma process needs to be followed by an intermediate H2O rinse (either deionized water or in-situ H2O vapor within the plasma reactor), then by a second CF4/N2H2 RF dry plasma step, and by a final H2O rinse. The intermediate H2O step appears to be crucial in making the fluorinated polymer residues more soluble, before their exposure to the second F-based dry plasma step and their final elimination through H2O rinse. The above process provides a reliable and cost-effective alternative method to solvent-based processing, with greater cleaning efficiency, less damage to device structures and less environmental impacts.