Annealing behavior of dilute Cu-X alloys (adding element X = transition metal and
rare-earth metal with less than 3 at %) was investigated in terms of resistivity, internal stress, grain
growth and hillock formation. The resistivity increases with addition of impurities regardless of
kinds of adding elements. Generally, resistivity starts to decrease on annealing above 200 °C.
Among present Cu dilute alloys, Sn addition shows the lowest resistivity 2.5 μΩcm on annealing at
400 °C. However, compared with a pure Cu film, salient grain growth of present dilute alloys does
not takes place even at temperatures above 300 °C , where the grain size is nearly the same as that
of as-deposited films. In-situ surface observation using an atomic force microscope (AFM )
revealed that hillocks did not grow on cooling stage (under tension), but started to form on heating
stage (under compression). The scanning electron microscopy (SEM) observation of hillocks thus
formed in present dilute alloy films shows that the external appearance of these defects was quite
different from those observed in Al and Al alloy films. They most likely grow with a preferential
crystal plane, not irregular growth like Al and Al alloy films. The internal stresses in most of the
present as-deposited dilute Cu alloy films were nearly zero or compression of –25 to –100MPa, and
upon annealing, they started to increase in tensile manner due to thermal stresses induced by the
mismatch of the thermal expansion between substrates and deposited films. A large stress relaxation
started to occur above 250°C, associating with a large number of hillock formation.