A photosensitive-BCB on laminate technology (MCM-LD)

As Multichip Module (MCM) technology has evolved from research to commercial production, cost has become the important issue for implementation. Manufacturing schemes are incorporating those processes and materials which take advantage of the most cost effective technologies to meet the specific performance requirements for a given application. The work described in this paper demonstrates how laminate based MCM technology (MCM-L) and deposited dielectric technology (MCM-D) can be combined to form a low cost solution for systems requiring high density interconnections. The use of laminate board technology to fabricate the relatively low density interconnect portion of the multilayer structure, allows one to take advantage of the well established and highly cost competitive printed wiring board (PWB) industry. Deposited dielectric technology takes advantage of the high density capabilities, normally associated with MCM-D packaging, to increase performance. Benzocyclobutene (BCB) is a well suited dielectric material for a laminate/deposited dielectric application (MCM-LD) since it can be cured at relatively low temperatures (220-275°C). Additionally, the use of BCB as the interlayer dielectric provides a stable copper/BCB interface, excellent planarization over rough topographies, and exhibits very low moisture absorption. Several low cost processing techniques were demonstrated as part of this MCM-LD program. These include an inherently photosensitive BCB formulation as the thin film dielectrics, meniscus coating as the large area deposition process for the photosensitive-BCB, and an in-line belt furnace for Rapid Thermal Curing (RTC). A two layer module was fabricated to demonstrate the feasibility of this MCM-LD process flow. This paper describes the processing issues and techniques associated with such a hybridized interconnection technology