Investigation of Cu-to-Cu Bonding Featuring Indium Passivation and a Tin Diffusion Barrier Layer
Journal
2025 International Conference on Electronics Packaging and iMAPS All Asia Conference (ICEP-IAAC)
Part Of
2025 International Conference on Electronics Packaging and iMAPS All Asia Conference (ICEP-IAAC)
Start Page
199
End Page
200
Date Issued
2025-04-15
Author(s)
Abstract
This study investigates the interfacial reactions among solid copper, tin, and indium. Samples were fabricated by sequentially electroplating 3 μm Cu, 5 μm Sn, and 5 μm In onto a silicon substrate. The results indicate that Sn and In completely react at room temperature, forming β-In3Sn and Y-InSn4, Additionally, a thin and stable Cu-In intermetallic layer, Cu(In, Sn)2, is observed between the Cu substrate and the Y phase. The effectiveness of Cu-to-Cu bonding with In passivation and an Sn diffusion barrier is evaluated. The bonding process was performed via thermal compressive bonding (TCB) at 150°C under 2 MPa for 1 minute. The findings reveal that while the Sn passivation layer does not entirely prevent In diffusion into Cu, it significantly slows down intermetallic formation. This passivation approach enables Cu bonding under mild processing conditions, reducing the need for high temperature and pressure.
Event(s)
24th International Conference on Electronics Packaging and iMAPS All Asia Conference, ICEP-IAAC 2025, Nagano, 15 April 2025 through 19 April 2025. Code 209021
Subjects
3D IC
Cu-to-Cu bonding
Diffusion barrier
In passivation layer
Intermetallic compound
Publisher
IEEE
Type
conference paper