TI-DIFFUSION BARRIER IN CU-BASED METALLIZATION

Reliability investigations, with or without a barrier layer, have been performed to study the penetration of copper into thermal oxide as a function of temperature and applied electric field. No copper diffusio n was detected without a barrier into 100 nm thick oxide for temperatu re stress as high as 450 degrees C for one hour and for bias temperatu re stress (BTS) as high as 300 degrees C for 8 h at 1 MV/cm. This abse nce of diffusion was observed when thermal annealing was performed und er vacuum. A 20 nm thick titanium layer was used as a diffusion barrie r/adhesion promoter between the copper and the oxide. The devices usin g this barrier were not affected by a temperature stress of 600 degree s C for 10 h and by BTS even at 450 degrees C for 2 h at 1 MV/cm.