High-Precision Wafer-Level Cu–Cu Bonding for 3-DICs

A high-precision Cu-Cu bonding system for 3-D ICs (3-DICs) fabrication adopting a new precision alignment methodology is proposed. A new pressure profile control system is applied in the thermocompression bonding process. Experimental results show that the alignment capability is 250 nm or better, with similar overlay accuracy (|average| + 3σ) for permanent bonding. These developments are expected to contribute to the fabrication of future 3-DICs.