3-D Stacking Using the GE High Density Multichip Module Technology

To solve the interconnect and packaging problems associated with large distributed processing systems and of mass memory systems, the GE Corporate Research and Development Center has developed a 3-D stacked multichip module (MCM) technology. This technology uses, as building blocks, modules produced by the GE High Density Interconnect (HDI) embedded chip process. The fundamental features of this 2-D HDI polymer film overlay process, which are used to interconnect a number of chips within a common substrate, are extended to the interconnection of a number of multichip substrates. The 2-D HDI substrates with their essentially planar surface, and chips recessed beneath the interconnect structure, are ideally suited for direct 3-D stacking of one substrate upon another. The thermal path of the stack is directly through the substrate to the base of the stack. The substrate I/O connections are brought to the substrate edges for vertical connection within the stack. The multilayer lamination and thin film interconnect processes used to interconnect the chips, i.e. polyimide film dielectric, laser formed vias, and electroplated copper metallization, are then applied to one or more of the four edges of the stack. This paper will describe the basic 2-D HDI process and how it was extended to the 3-D interconnection of multichip substrates.