Towards Selective Cobalt Atomic Layer Deposition for Chip-to-Wafer 3D Heterogeneous Integration

The feasibility of a 3D bonding technology for ultra-dense input/output (I/O) interconnects using cobalt selective atomic layer deposition (Co ALD) is explored with a preliminary testbed. Steady-state thermal simulations benchmark the Co ALD bonding technology to investigate the potential thermal benefits compared to conventional bonding technologies such as microbumps $(\boldsymbol{\mu}-\mathbf{bumps})$ and hybrid bonds. Preliminary testbeds containing horizontal Cu/100 nm Gap/Cu structures are fabricated to show the feasibility of using Co ALD as a high-density Cu-Cu interconnect bonding technology. SEM and XPS are used to characterize the test structures, showing that after 400 cycles of Co ALD deposition, the 100 nm gap is filled between the aligned Cu pads.