Photopatterning of Low Dielectric Constant Cycloolefin Polymers Using Azides and Diazirines

Polymers are widely used as insulators in electronic devices. Low dielectric constant polymers are desirable since this lowers the potential for unintentional crosstalk and inductive coupling between conductors. Attempts to photopattern a low dielectric constant polymer, poly(5-hexyl-2-norbornene) (poly(1)), with a bis(azide) were unsuccessful. Incorporation of butenyl pendent groups improved patterning, but the dielectric constant of the cross-linked film was relatively high (2.60). A difunctional bis(diazirine) (compound 4) was synthesized and characterized by NMR and MS. Compound 4 rendered unreactive, aliphatic cycloolefin polymers such as poly(1) photopatternable, yielding negative tone patterns with good resolution. The dielectric constant of films cross-linked with compound 4 was substantially lower than the films cross-linked with bis(azide) (2.09 for poly(1)).