Role of passivation etch polymers in interfacial delamination for polymeric low-k dielectrics

For copper/low-dielectric constant (low-k) interconnects, delamination at the dielectric-barrier metal interface has been studied. In particular, the role of deposited etch polymers used for sidewall passivation on the integrity of this interface has been examined. We found that etch polymers were deposited on the flat (horizontal) surfaces used as low-k masks. Fluorinated polymeric etch residues of approximately 10–20 Å in thickness were detected using time-of-flight secondary ion mass spectroscopy and Auger electron spectroscopy. Although these etch residues resulted primarily from the etch sidewall passivation process, no detectable residue was found on the sidewalls themselves. The presence of the polymeric residue was found to compromise the integrity of the dielectric-barrier metal interface. Removal of the residue could be accomplished through either sputtering or by a concluding O2 plasma flash step during etch. Using these techniques, significant improvement in dielectric-barrier metal interfacial integrity could be obtained.