Growth behavior of copper metalorganic chemical vapor deposition using the (hfac)Cu(VTMOS) precursor on titanium nitride substrates

Abstract

Metalorganic chemical vapor deposition of copper using the thermally stable (hfac)Cu(VTMOS) [C10H13O5CuF6Si: 1,1,1,5,5,5-hexafluoro-2,4 pentadionato(vinyltrimethoxysilane) copper (I)] precursor has been carried out on TiN substrates prepared by physical vapor deposition (PVD) and rapid thermal processing (RTP). The apparent activation energies over substrate temperatures ranging from 160 to 220 °C were about 7.5 kcal/mol on the PVD-TiN and 9.7 kcal/mol on the RTP-TiN. The higher growth rate of the copper deposit on the RTP-TiN could be ascribed to the increase in nucleation sites and the higher electron catalytic reactivity, resulting in enhancement of copper nucleation density in the initial stages of film growth. The copper deposits revealed polycrystalline phases with a preferred orientation of (111), and impurities within the films were below the detection limit of Auger electron spectroscopy. As substrate temperature increased, the copper films on the PVD-TiN developed as a columnar structure according to the Volmer–Weber growth mode, and on the RTP-TiN a nearly equiaxed structure was formed presumably by Stranski–Krastanov grain growth. The electrical resistivity of the deposits on the PVD-TiN and the RTP-TiN was in the range 2.8–5.4 μΩ cm for 1500–3100 Å film thicknesses and 4.4–6.2 μΩ cm for 2300–4300 Å film thicknesses, respectively. With increasing film thickness, the electrical resistivity of the copper layers linearly increased on the PVD-TiN, while it gradually decreased on the RTP-TiN. Consequently, the variations in the electrical resistivity of the deposits could be explained by changes in microstructures of the copper films, due to different growth behavior of copper on the two types of substrates.