Etching Residues of Sputtered Ta Film Using Chlorine-Based Plasma

Ta films are used as X-ray mask absorbers. Spindly etching residues of the Ta film are generated on a polished SiC film when using chlorine-based plasma. We found that etching residues were generated because of microholes which exist on the polished SiC film surface, and that etching residues generally originated from the steep slope of the substrate. For the Ta film on the Si slope, a broad peak of beta-Ta(410) was observed in addition to that of beta-Ta(002), which is found on the Si plane. An orientation different from beta-Ta(002) appears to reduce the dry etching rate. We attempted Ar sputtering of the SiC surface to smooth the slopes in the SiC microholes. Etching residues did not originate in the case of the Ta film deposition on the polished SiC film after Ar sputtering. Therefore, Ar sputtering of polished SiC is very useful for avoiding the formation of etching residues.