Specific Process Knowledge/Thin film deposition/Deposition of Gold/Adhesion layers: Difference between revisions

For the chemical distribution of the elements in the 2nm Ti/2nm  Au sample, the STEM-EDX measurements at the Ti/Au interface showed the presence of a continuous Ti layer below the Au layer (Fig. 8a). The analysis of the 2nm Cr/2nm Au sample showed instead the presence of Cr throughout the whole thickness of the Au layer (Fig. 8b). Since Cr and Au were deposited sequentially and not by a co-deposition process, this result suggests a strong inter-diffusion. The 2nm Cr/20nm Au sample was also investigated, to understand the degree of inter-diffusion for a thicker Au layer (Fig. 8c). In this case the inter-diffusion between the elements was incomplete, being present for a thickness of 2-3 nm. This suggests that the diffusion process is limited to such a thickness when Cr and Au are deposited at room temperature.

To verify the chemical composition of the samples, in particular to investigate a possible presence of oxygen in the adhesion layer, STEM-EELS analysis was used. A line scan across the layer interfaces of the 2nm Ti/2nm Au sample shows the presence of a Ti core loss L3 edge at 460 eV and an L2 edge at 465 eV. A SiO2 O-K edge is visible at 538 eV, while the O-K edge of O bounded to Ti is found at 532 eV (Fig. 9a). The same investigation was performed on the 2nm Cr/2nm Au sample (Fig. 9b). The analysis showed a Cr L3 edge at 585 eV and an L2 edge at 594 eV. The SiO2 O-K edge is visible at 545 eV, while at 540 eV a weak OCr-K edge of O bounded to Cr is visible for a limited thickness below Au. Furthermore, the Cr edge presents a compositional tail along the scan direction, which confirms diffusion into the Au layer. For the length of the tail there is no presence of OCr-K edge, indicating that Cr inside Au is in metallic form. This is in good agreement with the observed diffusion, which involves only metallic Cr.