HARDNESS HIGHLY DISPERSED FILMS GETEROSITEMY Ag-Cu
Abstract
The films obtained during vacuum condensation Ag and Cu on the surface of the substrate
have a nanocrystalline structure induced by the formation of phases in the solid solution of Ag and
Cu in the Ag Cu, and their hardness in a broad range of component concentrations exceed the calculated
value. Currently, there is no unambiguous interpretation of abnormal hardness of nanocrystalline
films of Ag-Cu, and no clear mechanism of hardening. Therefore, the aim of the present work —
a comparative evaluation of the hardness of nanocrystalline Ag-Cu films and determination of the
causes of high hardness film composites Ag-Cu. Films Ag, Cu and Cu-Ag with thickness 1.0—1.5 micrometers
was prepared by thermal evaporation and condensation under vacuum of 5·10–4 Pa corresponding
metals from one or two sources on the surface is thermally oxidized wafer (111) Si with an
oxide layer thickness about 0.5 microns at a temperature of the substrate TS = 300 and 570 K and
a condensation rate of about 30 nm / sec. Surface morphology of the films was investigated by AFM,
mechanical properties was investigated by the method of nanoindentation with a maximum load of
5 mN and 10 mN.
Analysis of the nanoindenter fingerprint and film structure Ag, Cu and Cu-Ag condensed at TA = 300 К
showed that the difference in the mechanisms of plastic deformation associated with the dispersion
structure, reflected on the surface morphology in an indentation. In the case of the dislocation mechanism
of action observed sheet output of the film material at the edge of the indenter and the result
is a compact hillock on the edge of the print. With decreasing grain size becomes the main mechanism
of deformation process of grain boundary sliding. In this case, the indentation results in the spread
of mechanical stress over a considerable portion from the edge of the indenter and the resulting spread
of the hillock is formed larger and the maximum height thereof smaller. Nanoindentation data show
that film hardness Ag-Cu, condensed with TA = 300 K greater than the hardness value as a single-phase
films and film composite Ag-Cu, obtained by TA = 570 K.
According to the results of nanoindentation are constructed curves H / Er from hs/hc and then determine
the maximum hardness (Hmax) of the film heterostructures system Ag-Cu in different structural
states: for amorphous-nanocrystalline Hmax = 17 GPa for submicrocrystalline Hmax = 20 GPa. Thus,
it is shown that the equivalent thermal condensation modes film composite Ag-Cu thickness of about
1 micron, the resulting co-sputtering of metal, has a higher hardness than the film of Ag and Cu.
Increased hardness heterophase film composite Ag-Cu as compared with single-phase films of metals
is due to its amorphous-nanocrystalline structure. AFM study of the surface morphology of the
films Ag, Cu and Ag-Cu composite in the indenter and the film structure allowed us to conclude about
the change of the mechanism of plastic deformation in the changes of dispersion of metal films.
The results are of interest in the VLSI technology in creating systems metallization interconnect
electromigration resistant, as well as in numerous applications (fine coating, wear resistance electrical
contacts, etc.).
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