Journal
ELECTRONIC MATERIALS LETTERS
Volume 17, Issue 5, Pages 392-398Publisher
KOREAN INST METALS MATERIALS
DOI: 10.1007/s13391-021-00299-4
Keywords
3D packaging; Chip stacking; Cu bonding; Cu interconnect; Copper nitride; Passivation; Plasma treatment; Wafer bonding
Categories
Funding
- Basic Science Research Program through the National Research Foundation of Korea (NRF) - Ministry of Science and ICT [NRF-2018R1A2B6003921]
- MOTIE (Ministry of Trade, Industry Energy) [20003524]
- KSRC (Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device
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Protecting the copper surface from oxidation is crucial for Cu-Cu bonding, and the copper nitride nanolayer can effectively prevent further oxidation, lowering the bonding temperature of Cu-Cu bonding.
Cu-Cu bonding is a key process in fine pitch Cu interconnect in 3-dimenssional Si integration. Despite the excellent electrical property and pattern ability of Cu material, the Cu-Cu bonding process is affected by the high bonding temperature and easy oxidation. Thus, the ability to protect the copper surface in a reactive air environment is very important in Cu-Cu bonding, especially for die-to-wafer Cu bonding applications. We studied Cu-Cu bonding using a copper nitride nanolayer as an antioxidant passivation layer and investigated the stability of the copper nitride nanolayer over 7 days and its decomposition capability across temperatures of up to 400 degrees C. We found that the copper nitride (Cu4N) nanolayer formed by two-step Ar/N-2 plasma treatment protected the copper surface from further oxidation in the air, and that the energy required for thermal decomposition of the copper nitride nanolayer in this study was about 29.6 kJ/mol. It can be seen that the bonding temperature of Cu-Cu bonding can be sufficiently lowered by using a low-temperature decomposition property of copper nitride. [GRAPHICS] .
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