Analysis of Nickel Silicides by SIMS and LEAP

Abstract

Ni-silicides formed by a variety of processing techniques were studied with secondary ion mass spectroscopy (SIMS) and local electrode atom probe (LEAP registered ) analysis. SIMS provided 1-D chemical analysis over an approximately 60 micron diameter area. LEAP provided 3-D atom identities and locations over an approximately 100-150 nm diameter area. It was determined that the 200 deg. C drive-in anneal results in a Ni{sub 3}Si{sub 2} phase, which is converted to NiSi at temperatures between 360 deg. C-400 deg. C. LEAP detects no As or Pt segregation after the 200 deg. C drive-in anneal, but did quantify As segregation of up to 7% of the material composition just inside the NiSi-Si interface after the phase-formation anneal. The presence of oxygen at the interface results in a silicide chemical surface roughness of up to 3.5 nm as compared to 0.5 nm with a clean, non-oxidized surface. Silicide stability was demonstrated over the phase-formation-temperature range of 360 deg. C - 400 deg. C including when a second rapid thermal anneal step was used. LEAP analysis was also able to quantify the surface roughness of the interface as a function of anneal temperature and the non-uniform Pt and As distribution across themore » silicide surface as viewed in 2-D surface projection.« less