Integrated Systems [systems on a chip]

Integrated Systems are defined as batch-fabricated interconnections of complex digital integrated circuits with analog interface circuits and transducers, such as sensors. By providing the cost, performance and reliability levels of monolithic integration, they offer potential advantages over multi-chip modules assembled with packaging technology. This paper studies the required process technology, as well as design, test and packaging issues, for integrating wide varieties of systems. The goal is to delineate the necessary steps in bringing Integrated Systems to market within a realistic period. With monolithic integration as the ultimate aim, a multi-chip entry point is identified that can start system technology on a learning curve of cost reduction using the same scaling principles that drive integrated circuits. Three challenges to be surmounted are identified in streamlining the I/O's and progressing along a learning curve, namely I/O scaling, I/O loading, and full-functional test. The "composite IC" is the entry point. A large chip, containing only global interconnects and power distribution, acts as a silicon backplane. Subsystem-chips, such as digital microprocessors or sensors, are flip-chip mounted using the accuracy of MEMS processing to fabricate "snap-together" physical and electrical interfaces with high reproducibility. While similar to conventional MCM's, this chip-to-chip connection has few compromises over on-chip connections. By keeping the fabrication responsibility within one organization, just as in monolithic chips, there is no need for incoming inspection. Added ESD protection and test-head loading are avoided on interior nodes by a new intra-factory method of testing.