Enhanced Copper Bonding Interfaces by Quenching to Form Wrinkled Surfaces

Area of Science:

• Materials Science
• Semiconductor Manufacturing
• Nanotechnology

Background:

• Moore's Law is nearing its physical limits, necessitating new approaches for semiconductor miniaturization.
• Three-dimensional integrated circuits (3D-ICs) offer a promising alternative, with copper-to-copper (Cu-Cu) bonding being a key enabling technology.
• Low atomic diffusion rates below 300 °C in Cu-Cu bonding create weak interfaces and reliability concerns.

Purpose of the Study:

• To investigate a novel quenching treatment for Cu films to enhance Cu-Cu bonding.
• To address the challenge of weak interfaces in 3D-ICs due to low-temperature bonding limitations.
• To improve the reliability of nanometer-scale integrated circuits.

Main Methods:

• A quenching treatment was applied to the Cu film surface, inducing strain energy.
• Variations in thermal expansion coefficients between the Si substrate and Cu film created a wrinkled surface morphology.
• Cu-Cu bonding was performed at 300 °C for 2 and 4 hours after the quenching treatment.

Main Results:

• The quenching treatment induced strain energy and a wrinkled surface morphology in the Cu film.
• Significant grain growth was observed at the Cu-Cu bonding interface after bonding at 300 °C.
• The bonding interface was effectively eliminated, indicating a robust bond.

Conclusions:

• The developed quenching treatment successfully enhances Cu-Cu bonding at temperatures below 300 °C.
• This method mitigates weak interface issues, paving the way for more reliable 3D-ICs.
• The technique offers a viable solution for overcoming Moore's Law limitations in semiconductor scaling.