TiW adhesion to PMDA-ODA polyimide. Surface and interface chemistry

Practical adhesion of dissimilar materials is affected by surface/interface chemistry, surface roughness and properties of materials making the interface. In this paper TiW peel adhesion to pyromellitic dianhydride - oxydianiline (PMDA-ODA) polyimide has been investigated with focus on surface and interface chemistry. The Pl was exposed to tetramethylammonium hydroxide (TMAH) prior to cure followed by Ar-sputtering with and without prior exposure to CF4-RIE. PI surface chemistry was characterized before and after plasma modifications using X-ray photoelectron spectroscopy (XPS). TiW/Pl adhesion follows: no plasma treatment < Ar-sputter ≈ CF4-RIE + Ar-sputter. Because the peel locus of failure (LOF) is near to the metal/PI interface but within the PI, the interfacial chemistry can be investigated using the peeled samples. Metal carbide formation with untreated PI was detected, while samples exposed to CF4-RIE and/or Ar-sputtering prior to interface preparation do not show the presence of this species.