| AVS 55th International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF-TuM |
| Session: | Applications of Atomic Layer Deposition |
| Presenter: | S.K. Park, University of Texas at Dallas |
| Authors: | Y.J. Chabal, University of Texas at Dallas S.K. Park, University of Texas at Dallas J. Kwon, University of Texas at Dallas M. Dai, University of Texas at Dallas R. Kanjoliab, SAFC Hitech R. Odedrac, SAFC Hitech Ltd., UK N. Boagd, University of Salford, UK |
| Correspondent: | Click to Email |
Ruthenium is a potential capacitor electrode material for DRAMs and FRAMs, and potential gate metal MOSFETs due to is relatively high work function (4.7eV).1 There is also recent interest in Ru as a combined barrier and seed layer for copper. Since atomic layer deposition (ALD) is technique of choice for deposition of thin and conformal film growth even on structured surfaces such as trenches and via holes, there is an active search for Ru ALD precursors possessing appropriate physical and chemical properties, which are important for the development of a proper deposition process. There is also the need to understand the chemical interaction of these new precursors with various surfaces and the mechanism of ALD growth to advance the field. So far, surface nucleation, overall interface formation and growth mechanisms are not well understood since most of film characterization has been performed with ex-situ measurements. In this study, we present in-situ FTIR studies of ALD growth of Ru thin films on Si substrates using newly synthesized cyclopentadienyl methylruthenium dicarbonyl (CpRuMe(CO)2) and D2O. Film growth rates were determined from ex-situ RBS measurements. SiO2/Si(100) and atomically flat hydrogen-terminated Si(111) surfaces were used as substrates for Ru film growth. For the H/Si(111) substrate maintained at 300°C during growth, the first half-cycle Ru precursor pulse almost completely consumes the surface hydrogen as evidenced by the loss of monohydride Si-H stretching mode at 2084 cm-1, which suggests a very high reactivity of the precursor toward the H/Si(111) surfaces at 300°C. The initial Ru deposition on H/Si(111) is initially good at 300°C, then becomes harder (lower growth rate). The precursor reactivity strongly decreases at lower substrate temperatures, involving only 30% of the surface hydrogen at 250°C substrate temperature. More importantly, there is no measurable Ru deposition, presumably because of competitive surface reactions. The reactivity and Ru growth on oxides, specifically SiO2/Si(100) substrate, are surprisingly lower than on H/Si(111) substrates at 300°C. Despite this low growth rate, the IR spectra give clear evidence for ligand exchange and adsorption of surface species, making it possible to identify and quantify surface chemical reactions during the ALD process.
1 Titta Aaltonen et al., Chem. Vap. Deposition 9, 45 (2003).