Simplified low-temperature wafer-level hybrid bonding using pillar bump and photosensitive adhesive for three-dimensional integrated circuit integration

• Published in: Journal of materials science. Materials in electronics 2017-06, Vol.28 (12), p.9091-9095
• Main Authors: Yao, Mingjun, Fan, Jun, Zhao, Ning, Xiao, Zhiyi, Yu, Daquan, Ma, Haitao
• Format: Article
• Language: English
• Subjects: Adhesive bonding; Adhesives; Bonding strength; Characterization and Evaluation of Materials; Chemistry and Materials Science; Copper; Level (quantity); Low cost; Low temperature; Materials Science; Metal bonding; Nickel; Optical and Electronic Materials; Photosensitivity; Shear tests
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-017-6642-y

A simplified low-temperature wafer-level hybrid bonding process using Cu pillar bumps and photosensitive adhesive was reported, wherein Cu/SnAg/Ni–P micro interconnects were formed to achieve electrical interconnect and the sealing around adhesive played the role of mechanical reinforcement. The proposed hybrid bonding method has been applied to 8 inch wafer to wafer bonding. Two kinds of photosensitive adhesives, i.e., polyimide and dry film, were selected for adhesive bonding. Excess adhesive on the Cu/SnAg micro bumps was properly removed using simple and low cost lithograph process. In order to prevent the adhesive trapping in the metal bonding interface, the height of the Cu/SnAg micro bumps was 2 μm higher than that of the adhesives. Although hybrid bonding using polyimide and dry film can achieve seam free bonding interface, shear test results indicate that bonding strength using dry film is more robust, and dry film is more suitable for hybrid bonding in three-dimensional integration applications.