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High-density interconnect integrated circuits (ICs) have been realized on flexible organic substrate with the demonstration of excellent electrical yield and well maintained reliability. Long metal-via chain structures were pre-fabricated with 0.18-μm Cu-backend technology on Si-substrate and later transferred onto the organic substrates with wafer-transfer technology. By optimizing the transfer process with thin FR-4 (4 mil ≈0.1 mm), our results demonstrate that both Cu/USG and Cu/low-κ [Black-Diamond (BD)]-based interconnects can be reliably realized over the organic substrate. For via chain structures with via size ∼0.26 μm and via number ∼104, the yields were ≥90% and 85% at room temperature and at 100°C, respectively. The dielectric breakdown field of the Cu/USG transferred interconnect ICs has been characterized to be ≥5 MV/cm, which is comparable with the results on Si-substrate.