Verlag des Forschungszentrums Jülich
JUEL-3091
Pollak, Reinhard
Herstellung passivierter Au-Leiterbahnen und Charakterisierung ihres mechanischen Spannungszustandes
98 S., 1995
Abstract
1,2Jim thick Au filmes were deposited by electron beam evaporation on oxidized Si-wafers.
The stresses were investigated by x-ray diffraction methods between room temperature (RT)
and 420°C. The films showed biaxial tensile stresses of '" 200 MPa at RT and small
compressive stresses of s 50 MPa at 420°C. Wafer curvature measurements confirmed these
values. The unstrained lattice parameters were determined as they are necessary for the
evaluation of the triaxial stress in the passivated lines. They are in good agreement with the
bulk lattice parameter. Lines of I um, 2um and 6um width were obtained by
photolithography and ion etching and were passivated with a 0,5um 5i3N4 layer deposited by
a PECVD process at '" 350°C. The passivated lines show large triaxial stresses varying
between 450 MPa tensile stress at RT and 300 MPa compressive stress at 420°C. In contrast
to the films and also to unpassivated lines a nearly elastic behaviour is observed during thermal
cycling. Isothermal measurements showed also very little stress relaxation.
The observed stresses are in agreement with the expectations from the Eshelby theory. This
comparison gave no indication for void formation within the given temperature regime. This
conclusion is supported by small angle x-ray scattering and by cross sectional TEM both
showing no evidence ofvoid formation. Furthermore the stresses in the lines can be released by
corrosive processes at the interface between the passivation and the Au-lines without damage
of the passivation. This debonding can be achieved within hours or months and has been
established by cross sectional TEM. Together with the superior electromigration resistivity of
Au in comparison to AI this stress release by debonding migth be very advantageous to future
applications ofAu interconnects.
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