Title: Low-temperature direct copper-to-copper bonding enabled by creep on (111) surfaces of nanotwinned Cu
Authors: Liu, Chien-Min
Lin, Han-Wen
Huang, Yi-Sa
Chu, Yi-Cheng
Chen, Chih
Lyu, Dian-Rong
Chen, Kuan-Neng
Tu, King-Ning
Department of Materials Science and Engineering
Department of Electronics Engineering and Institute of Electronics
Issue Date: 12-May-2015
Abstract: Direct Cu-to-Cu bonding was achieved at temperatures of 150-250 degrees C using a compressive stress of 100 psi (0.69 MPa) held for 10-60 min at 10(-3) torr. The key controlling parameter for direct bonding is rapid surface diffusion on (111) surface of Cu. Instead of using (111) oriented single crystal of Cu, oriented (111) texture of extremely high degree, exceeding 90%, was fabricated using the oriented nano-twin Cu. The bonded interface between two (111) surfaces forms a twist-type grain boundary. If the grain boundary has a low angle, it has a hexagonal network of screw dislocations. Such network image was obtained by plan-view transmission electron microscopy. A simple kinetic model of surface creep is presented; and the calculated and measured time of bonding is in reasonable agreement.
URI: http://dx.doi.org/10.1038/srep09734
ISSN: 2045-2322
DOI: 10.1038/srep09734
Appears in Collections:Articles