PtSi contact metallurgy: Effect of silicide formation process

PtSi films have been formed by different formation processes using sputtered Pt. Two annealing sequences are compared: a single-temperature annealing at 550 °C and a three-temperature annealing at 200-300-550 °C; and three annealing gases are compared: forming gas, nitrogen, and oxygen. Silicide films formed using the single-temperature process all show incomplete reaction between Pt and Si, leaving a protective surface oxide layer of poor quality, which extends rather deeply into the PtSi film and is completely etched off by aqua regia. The silicide films formed by the three-temperature process in forming gas, however, show a complete reaction between Pt and Si, and a thin surface oxide layer with excellent protection of the PtSi layer from the subsequent aqua regia etching often needed for device fabrication.