Area selective deposition of ruthenium on 3D structures

Trends in device miniaturization have driven the adoption of new materials that, in turn, have enabled significant advancements in the field of process engineering and integration for semiconductor technology. Continued progress for device scaling is necessary and can be enabled by advances in lithographic techniques and deposition schemes. Thin-film deposition for spacers and etch stop layers has become a mainstay to enable and extend traditional 2D scaling into the 3D realm for fabricating advanced semiconductor devices. For processing 3D structures, controlled film deposition with subnanometer resolution in high aspect ratio features is desired. Area selective deposition (ASD) can be a powerful response to such a challenge. ASD is a type of thin-film deposition technique scheme that can be used to eliminate the need for several expensive and time-consuming lithography steps with fewer performance penalties. In this work, we show ASD of ruthenium (Ru) on 3D molybdenum (Mo)–silicon oxide (SiO₂) stacks by utilizing the inherent substrate preference of the Ru precursor to a H-terminated surface. In the best selectivity condition, our results show growth of ∼5 nm Ru on Mo, with no film growth on SiO₂. Changes in Ru growth kinetics were observed after dilute hydrofluoric acid (DHF) treatment for both surfaces. Post-DHF treatment, the Ru growth rate on Mo was reduced by 5%. However, on SiO₂ (after incubation delay), the growth rate was reduced by 94% compared to untreated surfaces. This translates to a very high difference in the growth rate of Ru on Mo vs SiO₂, even after considering the incubation delay. Finally, by using 3D topologies with high aspect ratio holes, we have highlighted that it is important to deconvolute the effects of precursor depletion and selectivity. To the best of our knowledge, this is the first demonstration of ASD of Ru on 3D structures without the use of any blocking layers. Therefore, these results demonstrate a new paradigm for ASD in 3D features.