R. Buchhold et al., A STUDY ON THE MICROPHYSICAL MECHANISMS OF ADSORPTION IN POLYIMIDE LAYERS FOR MICROELECTRONIC APPLICATIONS, Journal of the Electrochemical Society, 145(11), 1998, pp. 4012-4018
Citations number
18
Categorie Soggetti
Electrochemistry,"Materials Science, Coatings & Films
Polyimide films are now finding application in microelectronics and mi
croelectromechanical systems technology One problem with polyimide fil
ms is their tendency to adsorb water from ambient humid air, which can
cause significant changes in the mechanical and electrical behavior o
f these films and even lead to their failure. To find ways to minimize
water adsorption in polyimide films, we have studied different types
of polyimides by both analytical arid phenomenological means. It appea
rs that the process of water uptake is by sorption of water molecules
in micropores inside the polymer. The sorption of water in thin polyme
r films typically results in volume expansion. Past a certain saturati
on level, each sorbed water molecule causes an expansion of about 15 A
ngstrom(3), which is about half of the effective volume of the water m
olecule. If the expansion of the polymer film is restrained by adjacen
t inorganic layers, the result is humidity-induced compressive stress
in the polymer film. We have found that the amount of water uptake and
the resulting anisotropic swelling depend strongly on the particular
type of polyimide. In this paper, new experimental results are present
ed and discussed in detail.