Cu/Si(001) epitaxial growth: role of the epitaxial silicide formation in the structure and the morphology

This communication deals with the early stage of the growth of Cu on Si(0 0 1)-H at room temperature. A copper silicide layer of about 1-2 nm of thickness is evidenced by reflection high-energy electron diffraction (RHEED), Auger electron spectroscopy and transmission electron microscopy (TEM). HRTEM experiments show that the silicide structure is in agreement with the bcc beta-Cu0.84Si0.16 structure. With further deposition of Cu, TEM reveals a highly textured fiber structure with a weak in-plane misorientation (few degrees). Scanning tunneling microscope (STM) observations for different thicknesses show a quasi-continuous film structure with mounds of well-defined sizes and well-defined separation distances. The mean distance L deduced from the height-height autocorrelation function varies as L(t) similar to t(0.5) with Cu thickness t. This particular growth morphology evolution does not correspond to the expected self-affine behavior supported by most kinetic models (based on KPZ model). As a matter of fact, the characteristic distance L is comparable with the size of the grains revealed by TEM. Therefore, it seems that silicide formation at the early stage of copper deposition play an important role in subsequent copper film microstructure. (C) 2004 Published by Elsevier B.V.