Chip mounting and interconnection in multi-chip modules for space applications

The objective of this study is to develop processing knowledge and technology of three-dimensional multi-chip modules for space applications. The aim is to test the reliability as well as to optimize the different process steps. Bisbenzocyclobuthene (BCB) was chosen as the interdielectric material as it fulfills the requirements for space qualification and process compatibility. Integrated circuit chips have been mounted recessed in silicon using BCB as glue. Metal interconnects of thin-film aluminum are isolated with spin-on deposited BCB as an interlayer dielectric (ILD). Two layers of BCB, total thickness 30 µm, are needed to achieve chip edge step coverage. Via interconnections, minimum dimensions 100×100 µm 2 have successfully been patterned in a 30 µm thick BCB layer. Measuring I - V characteristics has validated the connections.