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We measure end-of-line polysilicon waveguide propagation losses of ~6-15 dB/cm across the telecommunication O-, E-, S-, C- and L-bands in a process representative of high-volume product integration. The lowest loss of 6.2 dB/cm is measured at 1550 nm in a polysilicon waveguide with a 120 nm x 350 nm core geometry. The reported waveguide characteristics are measured after the thermal cycling of the full CMOS electronics process that results in a 32% increase in the extracted material loss relative to the as-crystallized waveguide samples. The measured loss spectra are fit to an absorption model using defect state parameters to identify the dominant loss mechanism in the end-of-line and as-crystallized polysilicon waveguides.

Conformal copper films were deposited onto various copper diffusion barrier layers with catalytic hydrogen reduction of copper(II) hexafluoroacetylacetonate, Cu(hfa)2, in supercritical CO2. In the presence of 2−5 at. % of Pd(hfa)2 (relative to Cu(hfa)2), device quality copper films (resistivity 2.1 × 10-6 Ω-cm) could be obtained at temperatures as low as 70 °C. The amounts of Pd in the Cu films were found to be very low (∼0.2 at. %) throughout the bulk of the Cu films. Adhesion of Cu films onto barrier layers was strong despite no Cu seed layer being used. The bottom-up supercritical fluid deposition mechanism allowed Cu films to fill up small features patterned on Si wafers.