Future trends in wafer scale integration

The present status and future prospects of wafer-scale integration (WSI) are considered, where the area of an entire wafer is made available to increase the functional density. The requirements for fault tolerance, additional levels of metallization, excess power dissipation, process conservatism to achieve finite yield, and the nonoptimum nature of the Al/SiO2 transmission line for cross-wafer communication have made WSI noncompetitive with state-of-the-art VLSI and dense multichip hybrid packaging approaches. The greatest benefit is expected to be a much better reliability, partly due to an all-monolithic system and partly because of the hope that fault tolerance (an absolute requirement for WSI fabrication) can be extended to failure tolerance.