ABSTRACT
Deformable metal interconnects on a flexible substrate have been attracting extensive attention due to their potential applications in flexible circuits and devices. In this paper, as a candidate for deformable interconnects, buckled metal bilayer thin-films with different stiffnesses on a pre-strained compliant substrate were fabricated. Change in the as-buckled pattern was investigated as a function of the film geometry, metal types and the amount of pre-strain in the substrate. A 10-nm-thick Cr film was deposited onto a pre-stretched polymerized polydimethylsiloxane (PDMS) slab, followed by the deposition of Cu, Al or Mo layer with thicknesses of 10 to 40 nm using a line-patterned mask, and then the pre-strains were completely released. Theoretical models for the buckling wavelength and amplitude, based on the strain energy in the films and substrate, were in good agreement with the measured data for different thicknesses and stiffnesses of the metal bilayers in conditions in which the Young`s modulus of he films was modified for the bilayer films. The buckled wave became finer with a decrease in the film width, and composite film waves were obtained by patterning the films into the geometry with various widths on a substrate.
keyword : thin films, sputtering, buckling, atomic force microscopy, stretchable electrode
