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Sub-Micron-Accuracy Gold-to-Gold Interconnection Flip-Chip Bonding Approach for Electronics–Optics Heterogeneous Integration

High-precision integration has valuable meaning in heterogeneous convergent technology. In this paper we report on a new high-precision low-temperature bonding approach, capable of submicron alignment accuracy, based on the conventional ultrasonic flip-chip bonding technique and modified metal pad and bump elements. The interconnection pair made from a conductive-sloped hollow bonding pad (concave) and metal cone bump (convex) elements, i.e., misalignment self-correction elements, helps in aligning and maintaining the alignment between the chip and the substrate during stacking. By this method, the stacking accuracy can be improved significantly and effectively. Repeatable submicron (i.e., less than 500 nm) bonding accuracies are confirmed through experimental investigation. Moreover, reliable bond characteristics including electrical and mechanical properties are observed, validating the performance of the bonding approach. With these results, the proposed high-precision low-temperature bonding approach shows its suitability for heterogeneous electronics–optics integration applications.