Wafer-level Sn-Ag-Cu/SiO2 Transient Liquid Phase Hybrid Bonding (TLP-HB) Technology

Direct Cu/SiO2 bonding is an emerging bonding technology to achieve the high density and fine pitch interconnections, compared with the standard flip chip technology and the μbump technology. In the process of bonding step, the defect on the copper surface and the mismatch of the copper dishing weight would result in the property deterioration, even a complete electric failure. In this paper, to improve the bonding performance of the Cu-Cu bonding and reduce the difficulty of dishing height control, we promote a novel transient liquid phase hybrid bonding (TLP-HB) Technology, by using a deposited tin and silver bi-layer on the copper surface by the electron beam evaporation, which could change the solid phase diffusion process of Cu-Cu bonding into a transient liquid phase bonding process. The first part of this paper is to design and to fabricate the test wafer with the micro-fabrication technology. Wafer processing is achieved through the Damascus process, which includes the SiO2 thin film the deposition, the lithography, the dry etching, and the metal thin film deposition. The excess metal layer was stripped by lift-off process. The second part of this paper is the method to bond the silicon wafer and the glass wafer, which were aligned with the double-side alignment lithography machine. The bonding process was operated on the thermo-compression bonding machine under a high vacuum condition. Bonding parameters had been tested, and an appropriate process profile had been suggested. The hybrid bonding interface mechanism had been studied for both the metal bonding area and the dielectronic bonding area. In addition, the specific contact resistance for these interconnection joints were also discussed, based on the experimental measurement.