| AVS 55th International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF-TuM |
| Session: | Applications of Atomic Layer Deposition |
| Presenter: | M. Dai, Rutgers University |
| Authors: | M. Dai, Rutgers University J. Kwon, Rutgers University S.Y. Park, University of Texas at Dallas L.S. Wielunski, Rutgers University Y.J. Chabal, University of Texas at Dallas Z. Li, Harvard University R.G. Gordon, Harvard University |
| Correspondent: | Click to Email |
In microelectronics, Cu is replacing Al for IC interconnects because of its lower resistance and higher melting point. For such microelectronics applications, a controlled metallization method to deposit very thin, uniform and conformal copper films is required. Atomic Layer Deposition (ALD) is the best method but is dependent on the synthesis of appropriate precursors. As recently reported,1 a novel precursor-Copper(I)di-sec-butylacetamidinate ([Cu(sBu-amd)]2)-has shown good performance for ALD of Cu films with high conductivity. Given its novelty and the stringent microelectronics application, it is important to probe the chemistry of both interface formation and thin film growth. We have used in-situ FTIR spectroscopy to monitor the reaction of [Cu(sBu-amd)]2 with two types of surfaces, the hydrogen-terminated Si(111) surface and silicon oxide surface, and to probe the next step of the ALD growth (H2 reduction of the adsorbed Cu precursor). The Cu film growth rates were determined using ex-situ RBS measurements. We find that the reactivity of [Cu(sBu-amd)]2 on these two surfaces is quite different. H/Si(111) surfaces are less reactive than oxidized surfaces. The IR vibrational spectra show that only ~20% of surface H react at 185°C. RBS measurements indicate that only 0.09 nm of Cu grows on H/Si(111) after 10 cycles. In contrast, there is a substantial loss of the SiOx TO and LO phonon mode intensity at 1075cm-1 and 1247cm-1 after the 1st Cu precursor pulse at 185°C on SiO2 surface, indicating that the surface SiO2 matrix chemically interacts with the precursor. Meanwhile, a broad absorption band centered at 1010cm-1 is observed, corresponding to the formation of Si-O-Cu bonds. Upon H2 exposure, the intensity of the SiOx phonon modes is partial recovered, suggesting that Cu atoms diffuse and agglomerate as the Cu precursor is reduced to pure Cu at 185°C. As agglomeration takes place (i.e. Si-O-Cu bonds are broken), the initial hydroxylated oxide surface is restored (in a hydrogen environment) and is characterized by the original SiOx phonon absorption. The ALD process is investigated by following the ligand exchange and ligand rearrangement on the surface. RBS measurements show 1.18nm of Cu is deposited on SiO2 after 10 cycles.
1Z. Li, S. T. Barry, R. G. Gordon, Inorganic Chemistry, (2005)44, 1728.