Chip to wafer direct bonding technologies for high density 3D integration

We demonstrate chip to wafer assembly based on aligned Cu-Cu direct bonding. A collective die surface preparation for direct bonding has implemented to develop dies direct bonding, defect free. An accurate pick and place equipment was adapted to ensure a particle free environment. After a damascene-like surface preparation, chips were bonded with less than 1μm misalignment. 400°C bonded daisy chains on die to wafer structure are perfectly ohmic. Concurrently, to overcome speed limitation of pick and place technique, a self-assembly technique chip is developed. This technique is based on capillary effect for self alignment and direct bonding for assembly. A less than 1 μm alignment accuracy and a 90 per cent self assembly process yield are obtained.