Copper-to-copper direct bonding on highly (111)-oriented nanotwinned copper in no-vacuum ambient

• Published in: Scientific reports Vol. 8; no. 1; pp. 13910 - 11
• Main Authors: Juang, Jing-Ye, Lu, Chia-Ling, Chen, Kuan-Ju, Chen, Chao-Chang A., Hsu, Po-Ning, Chen, Chih, Tu, K. N.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 17.09.2018; Nature Publishing Group
• Subjects: 14/28; 639/301/1005/1007; 639/301/1023/1026; Copper; Grain growth; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary); Temperature effects; Vacuum; Pillar Bump; Reverse Temperature Gradient; Nanotwinned Copper; Bottom Die; Annealing Twin Formation
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-018-32280-x

A vacuum-free Cu-to-Cu direct bonding by using (111)-oriented and nanotwinned Cu has been achieved. A fast bonding process occurs in 5 min under a temperature gradient between 450 and 100 °C. It is verified by grain growth across the bonded interface. To investigate the grain growth behavior, further annealing in the temperature gradient, as well as in a reversed temperature gradient, was performed. They showed similar recrystallization behavior with de-twinning. To analyze the de-twinning, we recall the classic model of annealing twin formation by Fullman and Fisher as comparison. Our case is opposite to the model of Fullman and Fisher. A mechanism of direct bonding by surface diffusion creep is proposed.