Aggressive Pitch Scaling (sub-0.5 μm) of W2W Hybrid Bonding Through Process Innovations

3D integration of dissimilar wafers through metal interconnect hybrid bonding has become common practice in industry from CMOS image sensors to 3D NAND memory at
$> \mathbf{1}\boldsymbol{\mu} \mathbf{m}$
pitches. Advanced 3D integration nodes requiring pitch scaling to
$\mathbf{sub}-\mathbf{0.5}\boldsymbol{\mu} \mathbf{m}$
face significant challenges in process control and material limitations. In this paper, through the use of advanced 300mm toolsets and process innovations we study the importance layout design, bonding dielectric, copper CMP recess control, and bonding overlay control to produce a high-quality bond interface at sub-500nm pitches. We also examined at which copper design density the material system begins to fail.