Ab initio analysis of nucleation reactions during tungsten atomic layer deposition on Si(100) and W(110) substrates

Novel insight into the mechanisms that govern nucleation during tungsten atomic layer deposition is presented through a detailed analysis using density functional theory. Using the calculated energetics, the authors suggest the most probable series of reactions that lead to monolayer formation on desired growth surfaces, Si(100) and W(110), during sequential doses of WF 6 and SiH 4. From this analysis, they conclude that a relatively high-energy barrier exists for initial nucleation of WF 6 on a silicon substrate; therefore, the system is limited to physical adsorption and is only capable of accessing nucleation pathways once the reaction barrier is energetically accessible. During early doses of WF 6, the initial silicon surface acts as the reductant. Results from this half-reaction provide support for the noncoalesced growth of initial W layers since nucleation is shown to require a 2:1 ratio of silicon to WF 6. In addition, the release of H 2 is significantly favored over HF production leading to the f...