Low-Temperature Cu/SiO₂ Hybrid Bonding with Low Contact Resistance Using (111)-Oriented Cu Surfaces

Area of Science:

• Materials Science
• Electrical Engineering
• Semiconductor Manufacturing

Background:

• Hybrid bonding is a critical interconnect technology for advanced semiconductor packaging.
• Achieving low-temperature and low-pressure bonding remains a challenge for copper (Cu) hybrid bonding.
• The crystallographic orientation of Cu surfaces significantly impacts bonding performance.

Purpose of the Study:

• To develop a low-temperature and low-pressure Cu/SiO2 hybrid bonding process.
• To investigate the effect of (111)-oriented Cu with high surface diffusivity on bonding characteristics.
• To achieve ultra-low specific contact resistance and high thermal stability in Cu-Cu joints.

Main Methods:

• Fabrication of Cu vias using electroplating with a high percentage of (111) surface grains (78%).
• Implementation of a wafer-to-wafer hybrid bonding scheme.
• Characterization of bonding parameters, including temperature, pressure, specific contact resistance, and thermal stability.

Main Results:

• Successful low-temperature (200 °C) and low-pressure (1.06 MPa) Cu/SiO2 hybrid bonding.
• Achieved the lowest reported specific contact resistance of 1.2 × 10^-9 Ω·cm² for Cu-Cu joints bonded below 300 °C.
• Demonstrated excellent thermal stability of the bonded joints up to 375 °C.

Conclusions:

• The use of (111)-oriented Cu with high surface diffusivity enables efficient low-temperature and low-pressure hybrid bonding.
• The developed process offers a promising solution for advanced interconnects requiring low resistance and high reliability.
• The study provides insights into the bonding mechanism, facilitating further optimization of hybrid bonding technologies.