Water-Induced Degradation of Metal/Polyimide Interfaces
The effects of deposition process conditions and post-deposition annealing on the adhesion of electron beam evaporated Cr, Ta, Nb and Cr/Cu alloys to fully cured polyimide have been evaluated by 90° peel testing and surface analysis. Auger analysis of the peel failure loci indicates a cohesive failure within the polyimide 5–20 nm from the metal interface for as-deposited and peeled samples which show peel strengths in the range from 60–80 g/mm depending on process conditions. After annealing in forming gas, degradation of peel strengths is always observed. Two modes of degradation occur following thermal processing. One mode results in the reduction of peel strengths by 25–35% to 45–55 g/mm. This is characterized, through Auger analysis, as a cohesive failure in the polyimide. A more dramatic failure results in peel strengths of 0–10 g/mm and is characterized as an interfacial failure at the metal oxide/polyimide interface. Results indicate that polyimide surface pre-treatment by RF Ar plasma creates a region of modified polyimide and metallic impurities which retard the degradation process.
KeywordsPeel Strength Interfacial Failure Cohesive Failure Auger Analysis Auger Depth Profile
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