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Island Edge Coverage By Metal Interconnects for Three Dimensional Circuits

Published online by Cambridge University Press:  15 February 2011

Rabin Bhattacharya
Affiliation:
Department of Electrical Engineering, Princeton University Princeton, NJ 08544, U.S.A.
Sigurd Wagner
Affiliation:
Department of Electrical Engineering, Princeton University Princeton, NJ 08544, U.S.A.
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Abstract

Three-dimensional integrated circuits is a new and exciting field that has been spurred on by the need for conformal displays and detector arrays. These circuits are fabricated by interconnecting rigid sub-circuit islands made on a flat, deformable substrate. To prepare for interconnects, we apply a patterned deformable sacrificial material over the flat substrate. We then deform the substrate, with the sub-circuit islands and the sacrificial pattern on it, to a spherical surface. Following deformation, we evaporate interconnect metal and then liftoff the sacrificial material, leaving only the metal lines that interconnect the islands. The maximum size for a circuit island to remain intact is proportional to the island's thickness. The larger the island has to be, the thicker it must be made to prevent it from cracking. For 50 μm thick Kapton E substrates, it was found that 40 μm square SiNx islandsmust be at least 0.5 μm thick.With such thick islands, sidewall coverage during evaporation of the interconnect metal becomes difficult because of the dome shape of the substrate. Moreover, during substrate deformation, there is delamination that occurs at the island-substrate interface. This delamination forms a gap between the edge of the island, and the substrate. Thick metalization that covers both sidewall and islandsubstrate gap, produces a yield of 97% for 10 micrometer wide aluminum lines.

Type
Research Article
Copyright
Copyright © Materials Research Society 2003

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References

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