Variable-frequency microwave curing of benzocyclobutene



Polymer dielectrics are widely used in the microelectronics industry for several applications including interlevel dielectrics, encapsulants, and passivating layers. To attain the desired properties, these materials need to be processed via lengthy cure cycles. Variable frequency microwave (VFM) processing has been investigated as a rapid curing alternative for the processing of thin-film dielectrics. Previous studies on epoxies and polyimide-based materials have shown significant reduction in cure time and improvement in properties on VFM processing. In this study, VFM curing of Dow Chemical Cyclotene™ 3022 benzocyclobutene (BCB) was investigated. The kinetics of the cure reaction were studied by Fourier transform infrared (FTIR) spectroscopy. FTIR studies indicated no significant differences in chemical structure between VFM and thermally cured films. The electrical, optical, mechanical, and chemical properties of VFM-processed films were characterized and compared with thermally processed films to determine the effectiveness of microwave processing. The results showed that VFM curing of BCB is feasible, and properties comparable to thermally cured films can be attained. The residual stress of partially cured BCB was lower for VFM processing than for traditional thermal processing. The residual stress in fully cured BCB was similar. Improvements such as shorter cure times and lower processing temperatures than conventional thermal processing can be achieved. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3055–3067, 2002; DOI 10.1002/app.10286