Low-Temperature Co-hydroxylated Cu/SiO₂ Hybrid Bonding Strategy for a Memory-Centric Chip Architecture

Area of Science:

• Materials Science and Engineering
• Nanotechnology
• Semiconductor Device Fabrication

Background:

• Ultradense interconnects (≤1 μm) are crucial for advanced integrated circuits.
• Current hybrid bonding methods face challenges in simultaneously achieving low-temperature bonding for both Cu-Cu and SiO2-SiO2 interfaces.
• Direct bonding of Cu-Cu and SiO2-SiO2 eliminates microbumps and underfill, simplifying fabrication.

Purpose of the Study:

• To develop a compatible low-temperature bonding mechanism for Cu/SiO2 hybrid platforms.
• To circumvent the contradictory surface chemistry requirements for Cu-Cu and SiO2-SiO2 bonding.
• To enable ultradense interconnects for future hyperscaling chip architectures.

Main Methods:

• Construction of a co-hydroxylated functional surface on a Cu/SiO2 hybrid platform.
• Optimization of Ar/O2 plasma activation and formic acid solution immersion to create a simultaneous -OH active layer on both Cu and SiO2 surfaces.
• Analysis of Cu-Cu interface quality, including atom diffusion, grain growth, and microvoids, at 200 °C.

Main Results:

• Successful establishment of a co-hydroxylated surface enabling low-temperature (200 °C) Cu/SiO2 hybrid bonding.
• Achieved a Cu-Cu interface with sufficient atom diffusion, substantial grain growth, and reduced microvoids.
• Effectively inhibited carbon-related interlayers at the SiO2-SiO2 interface, preserving interfacial performance.

Conclusions:

• The co-hydroxylated strategy provides a compatible mechanism for low-temperature Cu/SiO2 hybrid bonding.
• This approach facilitates the creation of ultradense interconnects with high interfacial integrity.
• The developed method holds potential for memory-centric chip architectures and monolithic-like performance in future integrated circuits.