July 2020 - Birgit Brandstätter Et al.
Chip-to-wafer hybrid bonding is needed as contact pitch and pad size decrease to the single micrometer range (5 micrometer or lower). Here, classical bonding technologies like themo-compression bonding and flip-chip with mass reflow are no longer sufficient, and hybrid bonding emerges as an attractive alternative. While the technology is well known in wafer-to-wafer processing, for chip-to-wafer at industrial speed and accuracy, new placement technologies and deeper understanding of accuracy behavior during the bonding process both are essential. This paper describes new optical recognition methods for small pads for accurate in-situ alignment before the bonding stroke as well as a new bond-head design and behavior for accurate placement at 200 nm at each point of the die, including large dies, and at speeds of 2000 units per hour.

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