A Mild Surface Activation Under Redox Gases Using Vacuum Ultraviolet Irradiation for Interconnection of Semiconductor Packaging

Efforts are underway to develop techniques for the direct bonding of chips with fine circuits to wafers without requiring soldering. Hybrid bonding is one such technique wherein the bonding surfaces of the chip and wafer are activated, aligned, and heated to achieve bonding. However, for optimal bonding, these surfaces must be free of oxides, particles, and organic contaminants. Vacuum ultraviolet (VUV)/O3 treatment uses 172 nm VUV light to modify material surfaces. During this process, active oxygen generated by the interaction of VUV light with oxygen acts on the material surface, decomposing and removing organic matter. However, surfaces subjected to VUV/O3 treatment become inactive owing to oxidation. To address this limitation, we developed a VUV-redox method, in which VUV light is irradiated in a redox gas environment. Our results demonstrate that surfaces subjected to VUV-redox treatment exhibit reduced organic contamination with minimal damage to surface components. This paper reports the results of a comparative analysis between the effects of VUV-redox and VUV/O3 treatments on the physical states of material surfaces used for semiconductor interconnections using X-ray photoelectron spectroscopy analysis.