Hybrid Au-Adhesive Bonding Using Planar Adhesive Structure for 3-D LSI

In this paper, we describe a hybrid bonding technology of Au microbump and adhesive using a planar adhesive structure for 3-D large-scale integration (LSI). Hybrid bonding means that both the microbump electrode and adhesive are simultaneously bonded. In 3-D LSI, the gaps between bonded chips are <;10 μm because the pitch of the microbumps is decreased. Conventionally, adhesive resin is injected into the gaps by means of capillary force. However, the filling of the gaps is insufficient due to surface conditions. To address this challenge, we evaluated hybrid bonding with a planar adhesive structure fabricated by chemical-mechanical polishing. The bonding results showed that connection between the Au bumps and adhesive filling in the 6-μm gap between bonded Si chips was achieved without readily visible void in the range of 6 mm × 6 mm. All 900 bumps were also electrically connected. The shear strength of the bonded sample was 13 MPa. Therefore, we determined that the proposed hybrid bonding technology is highly effective for 3-D LSI with fine-pitch microbumps.