@article{dea99baf23494a079306e165871e8fb3,
title = "Compensation of Surface Roughness Using an Au Intermediate Layer in a Cu Direct Bonding Process",
abstract = "Copper-copper (Cu-Cu) direct bonding assisted by direct immersion gold (DIG) was demonstrated. Cu-Cu direct bonding is a critical technology for inductively coupled memory interconnections. To solve the problems of conventional methods of Cu-Cu direct bonding, a plating process using DIG to form an intermediate layer was selected. The concept of the developed bonding process is to use deformation of DIG to compensate for the surface roughness of the Cu substrates during application of pressure and annealing. Using this method, precise surface flattening of Cu substrates is not necessary. Bonding can be achieved even in an air atmosphere. A sample bonded at a temperature of 350°C failed within the chip in a shear test. It was found that bonding can be achieved when the gold (Au) thickness is greater than the half of the surface roughness of Cu at the bonding temperature. Transmission electron microscopy-energy-dispersive x-ray spectroscopy revealed that Au diffused into Cu during bonding. The diffusion constant of Au into Cu was investigated through a numerical calculation. The obtained results showed good agreement with the literature values.",
keywords = "Au-Cu alloy, Direct immersion gold, copper direct bonding, magnetic coupling, memory package, three-dimensional interconnection",
author = "Hirokazu Noma and Takumi Kamibayashi and Hiroyuki Kuwae and Naoya Suzuki and Toshihisa Nonaka and Shuichi Shoji and Jun Mizuno",
note = "Funding Information: This work was partly supported by the Japan Ministry of Education, Culture, Sports Science and Technology (MEXT) Grants-in-Aid for Scientific Basic Research (A; no. 16H02349) and Scientific Basic Research (B; no. 16H04508). We acknowledge the MEXT Nanotechnology Platform Support Project of Waseda University. We thank C. Uyemura and Co., Ltd. for the DIG treatment. We thank Dr. Natasha Lundin from the Edanz Group (www. edanzediting.com/ac) for editing a draft of this manuscript. Funding Information: This work was partly supported by the Japan Ministry of Education, Culture, Sports Science and Technology (MEXT) Grants-in-Aid for Scientific Basic Research (A; no. 16H02349) and Scientific Basic Research (B; no. 16H04508). We acknowledge the MEXT Nanotechnology Platform Support Project of Waseda University. We thank C. Uyemura and Co., Ltd. for the DIG treatment. We thank Dr. Natasha Lundin from the Edanz Group (www.edanzediting.com/ac) for editing a draft of this manuscript. Publisher Copyright: {\textcopyright} 2018, The Minerals, Metals & Materials Society.",
year = "2018",
month = sep,
day = "1",
doi = "10.1007/s11664-018-6428-x",
language = "English",
volume = "47",
pages = "5403--5409",
journal = "Journal of Electronic Materials",
issn = "0361-5235",
publisher = "Springer New York",
number = "9",
}