Process Integration of High Aspect Ratio Vias with a Comparison between Co and Ru Metallizations

The integration of high aspect-ratio (AR) vias or supervias (SV) with a min CD
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= 10.5 nm and a max AR = 5.8 is demonstrated, allowing a comparison between ruthenium (Ru) and cobalt (Co) chemical vapor deposition (CVD) metallizations. Ru gave a resistance ~2x higher than Co when a 1.1 nm titanium nitride (TiN) film, realized by atomic layer deposition (ALD), was used as an adhesion/nucleation layer. The lowest SV resistance of 56 Ω at the median was obtained with 0.3 nm of titanium oxide (TiOx) ALD and Ru CVD. This configuration gave a 3.4x lower resistance than the equivalent scheme with 0.3 nm TiN ALD and 15% lower resistance than the stacked-via configuration (with 0.3 nm TiOx and Ru fill), meaning that an IR-drop penalty is avoided when compared to the stacked-via approach. A congestion reduction can also be expected from the CD reduction of the SVs as the exclusion area in the intermediate layer can be smaller. Thermal shock tests for both Ru and Co SVs produced no failure after 1000 cycles between −50 °C and 125 °C, and 250 hours.