Eliminating Cu-Cu Bonding Interfaces Using Electroplated Copper and (111)-Oriented Nanotwinned Copper

Tsan-Feng Lu ¹, Yuan-Fu Cheng ¹, Pei-Wen Wang ¹

⁰Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan.

Materials (basel, Switzerland) +

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July 27, 2024

View abstract on PubMed

Summary

This study introduces a novel Cu-Cu bonding method to eliminate weak interfaces by leveraging grain size differences and nanotwinned structures. This approach enhances joint reliability for ultra-high-density packaging applications.

Area Of Science

Materials Science
Metallurgy
Nanotechnology

Background

Copper-copper (Cu-Cu) joints are crucial for ultra-high-density packaging in advanced electronics.
Low atomic diffusion at typical processing temperatures creates weak interfaces, compromising joint reliability.
Existing methods struggle to effectively eliminate these detrimental bonding interfaces.

Purpose Of The Study

To propose and investigate a new method for eliminating bonding interfaces in Cu-Cu joints.
To enhance the reliability of Cu-Cu interconnects for high-end electronic packaging.

Main Methods

Utilized two types of Cu films with differing grain sizes for Cu-Cu bonding.
Leveraged grain size difference as the primary driving force for interface migration.
Employed columnar nanotwinned Cu structure as a secondary driving force to enhance migration.

Main Results

Successfully eliminated bonding interfaces in Cu-Cu joints bonded at 300 °C.
Observed significant migration of bonding interfaces and interfacial grain boundaries.
Demonstrated grain growth from one Cu film extending across the interface.

Conclusions

The proposed method effectively removes weak bonding interfaces in Cu-Cu joints.
Grain size difference and nanotwinned structures are key drivers for interface elimination.
This technique offers a promising solution for reliable ultra-high-density packaging.

Keywords:

Cu–Cu direct bonding grain boundary energy grain size distribution grains and interfaces microstructure nanotwinned Cu