Silicon hybrid wafer scale integration interconnect performance evaluation at RF frequencies

The RF electrical characteristics of hybrid wafer scale integration (WSI) interconnections on silicon-polyimide-aluminum and silicon-benzocyclobutene-aluminum substrates have been evaluated. The silicon wafer substrates were five inches in diameter, and each contained an identical set of 200 photolithographically patterned dielectric and aluminum interconnect test structures. The aluminum conductors were 2.5-μm thick, and half of the test structure conductors were 10-μm wide, while the remainder were 25-μm wide. Measurements between 5 kHz and 220 MHz confirmed the expected transmission line behavior manifested by the longer interconnections. The coupling levels in the 400 line/cm density structures are low (<-25 dB), but nevertheless significant, especially when digital logic applications requiring low-noise margins are anticipated. More important were the attenuation effects manifested by the longer aluminum interconnections when they were combined with low-impedance matched terminations