Tungsten: Sputter deposition and plasma etching

The plasma etch behaviour of magnetron sputtered tungsten films has been studied. Structured experiments using orthogonal arrays have been conducted to study the effects of deposition pressure, magnetron power and heating on film properties. Films which have low resistivity, bulk-like density and low tensile stresses (100–500 MPa) required for integrated circuit metallization have been obtained by optimizing the deposition conditions. Density and plasma etch rate in SF₆ have been measured. Plasma etch rates of tungsten films depend significantly on deposition conditions. Previously, oxygen incorporated into the film was thought to be responsible for high etch rates. Because large etch rate differences have been measured for nearly oxygen-free films, it is postulated that density, rather than incorporated oxygen, should be used to explain the differences in plasma etch rates.