Self-Assembly Process for 3D Die-to-Wafer using Direct Bonding: A Step Forward Toward Process Automatisation

Die-To-Wafer hybrid bonding process is foreseen by major microelectronic industrials as essential for the success of future memory, HPC or photonic devices. However, compared to Wafer-To-Wafer bonding, the process flow is much more complex and the die assembly throughput is significantly reduced, which do not facilitate process industrialization. CEA-LETI is been working since several years on development of self-assembly process in order to overcome the throughput issue. The use of water drop is very promising to self-align several thousand of dies per hour. This paper presents the latest developments to improve self-assembly robustness and move a step forward toward manufacturing. Firstly, a new material benchmark enabled to identify a foundry compatible hydrophobic material. Secondly, we demonstrated that the die and substrate realization can be fully achieved on automatized equipments. Finally, the process setup on standard pick and place equipment significantly improved the self-assembly process robustness: 98% of the dies were perfectly bonded, and 63% presented an alignment lower than 1μm with a low 5μm die edge topography, which is compatible with hybrid bonding design.