Area-selective ALD of Ru on nm-scale Cu lines through dimerization of amino-functionalized alkoxy silane passivation films.

The selective deposition of materials on pre-defined areas on a substrate is of crucial importance for various applications, such as energy harvesting, microelectronic device fabrication and catalysis. A representative example of area-confined deposition is the selective deposition of a metal film as the interconnect material in multilevel metallisation schemes for CMOS technology. This allows the formation of multilevel structures with standard lithographical techniques while minimizing pattern misalignment, overlay and improving the uniformity of the structures across the wafer. In this work, area-selective deposition of Ru by atomic layer deposition (ALD) is investigated using alkoxy siloxane dielectric passivation layers. In this work, a comparison of several silane organic SAM precursors in terms of Ru ALD ASD performance is reported. The importance of the surface areal concentration of the passivation molecules is demonstrated. According to the in-situ XPS film characterization, the ALD blocking layers derived from a (3-trimethoxysilylpropyl) diethylenetriamine (DETA) precursor have the ability to polymerise under ALD-compatible temperatures, such as 250 ºC, which leads to a significant inhibition of Ru growth up to 400 ALD cycles. At the same time, the DETA layer can be selectively removed from the oxidized Cu surface by rinsing in acetic acid, which allows to selectively deposit ca. 14 nm of Ru on Cu with no Ru detected on DETA-coated surface by RBS. The approach is successfully tested on 50 nm half-pitch patterned SiO2/Cu lines.