Effects of iodine on the initial growth of MOCVD Cu on MPTMS monolayer surface at a low temperature of 110 °C

Cu was deposited by chemical vapor deposition (CVD) on self-assembled monolayers of a 3-mercapto-propyl-trimethoxy-silane (MPTMS)-coated SiO2 substrate using (hfac)Cu(DMB) and C2H5I as precursors at 110 °C. The effects of iodine addition on the initial growth of Cu were investigated by scanning electron microscopy (SEM). For comparison, Cu was deposited without iodine on the MPTMS monolayer. The low temperature deposition of Cu without iodine showed that the initial growth of Cu particles is limited by the direct flux of Cu precursors on the growing Cu surface, which continues until active coalescence occurs. This results in a very low growth rate (1 Å/s) of Cu particles at the initial stage of particle growth. The addition of iodine significantly enhanced the surface-diffusion of Cu adatoms over the MPTMS surface and allowed the facile dissociation of Cu(hfac) adsorbed on the Cu surface. These two effects increased the growth rate of Cu particles to approximately 13 Å/s. However, the root square time dependence of the growth rate of Cu particles suggests that the iodine-enhanced surface diffusion of Cu adatoms is a major contributor to the increased growth of Cu particles.