Variable frequency microwave processing of materials for microelectronic applications.

摘要

Polymer dielectrics such as polyimides are widely used in the microelectronics industry for a variety of applications such as interlevel dielectrics and stress buffer passivation layers. Rapid curing alternatives are necessary to increase the throughput and lower the fabrication cost of devices. There is also a need to reduce the thermal budget in advanced electronic devices to mitigate the stress induced due to CTE mismatch between the silicon substrate and the packaging compounds. Novel, low-temperature selective processing methods are required to address these issues. In this study, variable frequency microwave (VFM) curing was investigated as a rapid, low-temperature curing alternative to conventional thermal curing. Several commercially available polymer dielectrics with different backbone chemistries currently of interest in the microelectronics industry such as benzocyclobutenes (BCB), polyimides and polybenzoxazoles were studied. The kinetics and mechanisms of the cure reactions in microwave-processed films were investigated. Structure-property relationships and their dependence on processing conditions were determined. The results from this study show that rapid VFM curing of polymer dielectrics is feasible giving properties comparable to traditional thermal curing in a much shorter cure time. Rapid curing of high performance dielectrics on low temperature organic substrates was demonstrated. Critical low-temperature processing issues were identified. Selective curing of electrically conductive adhesives and solder reflow by VFM processing were also investigated.