[Zurück]

A. Bittner, T. Bohnenberger, R. Engel, H. Seidel, U. Schmid:
"Morphological and Electrical Properties of Silver Thin Films Sputter Deposited on LTCC Substrates";
Journal of Microelectronics and Electronic Packaging (eingeladen), 5 (2009), 4; S. 169 - 173.

Screen printed noble metal thick films are commonly used as metallization on LTCC (low temperature cofired ceramics)
substrates. When, however, geometries with a lateral resolution
below 20 mm are needed for the realization of devices, alternative
techniques are needed, and they are provided by standard thin film
technology. To minimize conduction losses, silver (Ag) is favored
due to a low bulk resistivity. To evaluate the potential of Ag as
metallization, thin films are sputter deposited on glass and LTCC
substrates under varying conditions (i.e., plasma power) with different film thicknesses ranging up to 1.75 mm. The microstructure
of the Ag films is analyzed applying techniques such as scanning
electron microscopy, focused ion beam, and x-ray diffraction.With
the latter approach, a mean grain size of about 33 nm is measured
independent of plasma power used for Ag deposition. In contrast,
the texture strongly varies with deposition parameters resulting in
an enhanced generation of (111) planes at higher plasma powers
due to an increased adatom mobility. Furthermore, a higher degree
in (111) orientation results in a lower resistivity of the Ag
films. When the Ag films are postdeposition annealed at 500°C,
the resistivity decreases by a factor of 2 compared with the "as
deposited" state due to grain growth. Further, sublimation and
agglomeration effects dominate leading to an increase in surface
roughness and resistivity above average.

Thin film technology; LTCC; Ag, resistivity; microstructure; post deposition annealing