Structural integrity and thermal stability of TiN/CoSi₂ used as local interconnect in a self-aligned CoSi₂ process

The Tin/CoSi₂/Si structure is of interest for local interconnect applications on Si integrated circuits. The thermal stability of this structure at 850°C is explored for the case where the TiN layer is formed by reactive ion sputtering or by thermal nitridation of a deposited Ti layer. The stability of a Ti/CoSi₂/Si structure at 850°C also is investigated. AES, thin-film XRD, and cross-sectional TEM are employed to identify the nitridation and interface reaction products, their structure and composition, phase sequence and layer morphology. It is found that un-nitrided Ti reacts with both the CoSi₂ and the underlying Si. The XRD data suggest the formation of TiSi₂ and the interletallic Co₂Ti compound.