Interactions of Cu with CoSi2, CrSi2 and TiSi2 with and without TiNx barrier layers

Abstract

Interactions of Cu with CoSi₂, CrSi₂, and TiSi₂ with and without interposed TiN_x layers have been studied using Rutherford backscattering spectrometry, Auger electron spectrometry, x‐ray diffraction, and in situ sheet resistivity measurements. Cu diffuses through a preformed CoSi₂ layer to form the structure CoSi₂/Cu₃Si/Si(100). No dissociation of CoSi₂ has been observed. For the Cu/CrSi₂/Si system, the outdiffusion of Si leads to the formation of Cu₃Si/CrSi₂/Si at temperatures above 300 °C. At about the same temperature, Cu diffuses into a TiSi₂ layer and to the TiSi₂/Si interface to react with both Ti and Si forming Cu₃Ti, Cu₃Si, and Cu₄Si phases. A 50‐nm TiN_x layer prepared by reactive sputtering was observed to be an effective diffusion barrier between Cu and CoSi₂ or CrSi₂. A 30‐nm layer of TiN_x simultaneously grown with TiSi₂ by rapid thermal annealing proved effective between Cu and TiSi₂ up to 500 °C.