Abstract
The formation and thermal stability of nickel silicides on blank and patterned (001)Si have been studied by sheet resistance measurement, secondary ion mass spectroscopy (SIMS), transmission and scanning electron microscopy (TEM and SEM), glancing incidence x-ray diffractometry (GIXRD), high-resolution transmission electron microscopy (HRTEM) and Auger electron spectroscopy (AES).The formation of nickel disilicides on nitrogen implanted (001)Si was suppressed and shifted to a higher temperature by 50-100 0C. The sheet resistance was found to be nearly constant in a wide range of temperatures in nitrogen ion implanted samples. The diffusion of nickel atoms is thought to be retarded by the presence of nitrogen atoms. The presence of nitrogen ion can also improve the thermal stability of nickel disilicide. The effects of nitrogen on nickel silicide formation become more pronounced with increasing nitrogen dose.Compressive stress induced by backside SiO2 film on the silicon substrate was found to retard significantly the formation of Ni2Si, NiSi and NiSi2 on (001)Si. On the other hand, tensile stress induced by backside Si3N4 and CoSi2 films was found to enhance the formation of nickel silicides on (001)Si. The thickness of growing nickel silicide thin films was found to increase and decrease with tensile and compressive stress level, respectively. The results indicated that the diffusion of nickel atoms through Ni/Si and nickel silicide/Si interfaces is facilitated and retarded by the tensile and compressive stress, respectively.NiSi was observed to be the only silicide phase for the samples annealed at 500-800 0C with a thin interposing Pt layer. The sheet resistance maintained the same low level in a wide temperature range. Pt addition was found to retard significantly the formation of nickel silicides and enhance the thermal stability of NiSi thin films on (001)Si. For Ni (30 nm)/Pt(1.5 nm)/(001)Si, the process window of NiSi was extended to 500-800 0C. The effects of interposing Pt layer become more pronounced with an increase in the thickness of Pt layer. In patterned (001)Si, epitaxial NiSi2 was found to grow at annealing temperature as low as 400 0C. In contrast, for Ni (30 nm)/Pt(1.5 nm)/patterned (001)Si, the process window of NiSi was extended to 400-750 0C.