Surface morphology and electrical properties of copper thin films prepared by MOCVD

Thin copper films have been grown in a vertical MOCVD (Metal-Organic Chemical Vapor Deposition) reactor using bis(2,2,6,6-tetramethyl-3,5-heptanedionato) copper(II), Cu(thd)₂, as precursor. Deposition has been carried out in a pure hydrogen atmosphere (pressure: 3, 20 mbar) at different substrate temperatures (350–750 ° C). The films have been investigated by profilometry, four-point resistivity measurements, ESCA, AES, XRD, AFM, and Normarsky microscopy. An unusual dependence of the film thickness with deposition time has been observed. Rapid growth occurred in the first minutes resulting in badly conducting films (thickness below 1000 Å). Good electrical resistivities have been obtained above 2000 Å. AFM has been used to gain information about the surface morphology of the films with different thicknesses. The grain size and surface roughness increased with increasing film thickness. Small grains grew in the beginning and the electrical properties have been governed by the highly Ohmic bridges between the individual grains.