High thermal stability of Ni monosilicide from Ni-Ta alloy films on Si(100)

We investigated the thermal stability of NiSi using Ni-Ta alloy films on Si(100) substrate. After silicidation using one-step rapid thermal processing (RTP) at 500°C for 30 s, uniform NiSi layers were formed from both Ni/Si and Ni-Ta/Si systems. To compare thermal stability of NiSi formed by RTP at 500°C, an additional annealing was performed in a furnace at 600°C for 120 min after a self-aligned silicide (SALICIDE) process. In the Ni-Ta/Si system, the silicide layer exhibited a NiSi phase and a stable sheet resistance of 5 Ω/□ even after furnace annealing at 600°C for 120 min. In the Ni/Si system, however, the sheet resistance dramatically increased with an increase of annealing time due to phase transition from NiSi to NiSi₂. X-ray diffraction data and transmission electron microscopy images also suggest that the thermal stability of NiSi was remarkably improved by addition of Ta. In addition, it is confirmed that Ni_0.90Ta_0.10 film does not react with any dielectric materials (SiO₂,Si₃N₄) at an annealing temperature of 500°C. Conclusively, the experimental results strongly suggest that Ni-Ta film could be applicable to high performance sub-0.1 μm devices for SALICIDE processes.