Secondary ion mass spectrometry study of the thermal stability of Cu/refractory metal/Si structures

Evidence is presented for the blocking of Cu diffusion into SiO2 and Si by Ta and Ta/W barriers. The anneal was performed at 450 °C for 30 min. Here, W is rejected as a potential barrier for Cu technology. A Cr layer as thin as 200 Å is shown to limit diffusion into Si to ∼600 Å. The study also demonstrates the utility and versatility of secondary ion mass spectrometry for evaluating potential diffusion barriers, and the need for such corroborative characterization in light of the lesser sensitivity of Rutherford backscattering spectroscopy.