The Use of Segregated Hydrofluoroethers in Semiconductor Wafer Processing

In this paper, we demonstrate the use of segregated hydrofluoroethers (HFE) as effective co-solvents in semiconductor wafer processing. Three examples are provided, etching of silicon oxide, post-ash low-k dielectric repair and post-etch residue removal for porous low-k dielectrics. HFE/IPA/HF chemistries yield greater than a 50times increase in silicon oxide etch rate relative to similar HF concentrations in aqueous media. In addition, the HFE mixtures have a surface tension of ~14 dynes/cm versus water which has a surface tension of ~72 dynes/cm. The lower surface tension HFE etchants are particularly useful in processing fragile high aspect ratio structures. HFE/IPA co-solvent mixtures can be used to partially restore low-k dielectric properties for materials which have been damaged during a plasma ash process. Alternatively, the HFE/IPA co-solvent chemistries can be used to remove photoresist and post-etch residue in non-damaging Cu/low-k cleaning applications. Specifically, NMP addition to HFE/IPA removes photoresist, while the addition of 2000ppm of HF(49%) to HFE-71IPA selectively removes residue on copper and low-k surfaces yielding improved electrical performance