Correlation between the early stage of copper metal organic chemical vapor deposition and the material properties of thin film

Cu metal organic chemical vapor deposition has been performed on TiN/Si(100) substrates using Cu(I)(hfac)(vtms) at various substrate (110 less than or equal to T(s)less than or equal to 300 degrees C) and bubbler temperature (0 less than or equal to T-b less than or equal to 30 degrees C) conditions, in which the early stage of film formation characterized by scanning electron microscopy and in situ laser beam (lambda = 6328 Angstrom) reflectance measurement could be well correlated with the surface roughness and the electrical resistivity of the copper films developed in a later stage. All the reflectance versus deposition time curves showed a qualitatively similar shape consisting of three sequential parts: a rapid initial decrease to a minimum, an increase to a maximum, and a gradual decay to almost zero, in which the minimum and maximum roughly correspond to the onset and completion of island coalescence, respectively. As the T-s is raised and/or the Tb is lowered, larger islands were formed in a smaller density at the onset of island coalescence due to a lower nucleation rate. The surface roughness gradually develops with increasing film thickness after forming a continuous film, but it does not saturate at a thickness of similar to 2 mu m and shows a correlation with the average island size in the earlier coalescence stage,i.e., the smaller islands evolves to a smoother surface. Above the threshold temperature (T-s similar to 230 for T-b =30 degrees C) the copper islands begin to show facets and at even higher T-s large truncated polyhedron-shaped copper islands are formed, which upon coalescing leave many interfacial voids to result in a film with a very rough surface and a high electrical resistivity. The copper films deposited at 150 less than or equal to T-s less than or equal to 200 degrees C have a very low value of rho approximate to 2 mu Omega cm, which increases by a factor of similar to 2 when T-s is lowered to 110 degrees C. The latter was accompanied by the formation of smaller islands at the onset of coalescence, and therefore the increase in rho at T-s less than or equal to 150 degrees C was attributed to the electron scattering at the grain boundaries. (C) 1998 American Vacuum Society. [S0734-211X(98)01806-X].