Nanograin Cu-Cu Bonding for Low-Temperature Chip Packaging
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Solution Overview
Problem
Current Cu—Cu direct welding techniques require high temperatures (above 400°C) and time-consuming chemical mechanical planarization processes, making them unsuitable for semiconductor industry applications, especially for 5G chip packaging where low-temperature and efficient bonding is necessary.
Innovation Solution
The method involves compressing copper structures with nano-sized grain layers (5 nm to 500 nm average grain size and 10 nm to 10 μm thickness) under stress (0.1 MPa to 50 MPa) at temperatures between 100°C to 250°C for 1 to 30 minutes, eliminating the need for chemical mechanical planarization and enabling efficient Cu—Cu direct welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Cu—Cu direct welding is performed at high temperatures (above 400°C), then adequate Cu atom diffusion for bonding is achieved, but processing complexity and time increase due to additional CMP processes
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures (>400°C) to low temperatures (250°C or less), and modifies the surface structure parameter by introducing nanograin layers (5-500 nm grain size) to enable diffusion bonding under these milder conditions without requiring CMP processes
Solution Approach 2:
The patent performs preliminary surface modification by creating nanograin layers on copper surfaces before bonding. This preliminary action of surface structuring enables subsequent low-temperature diffusion bonding to proceed effectively without requiring additional CMP processes during the bonding stage
2Reliability
If conventional Cu—Cu direct welding is performed at high temperatures (above 400°C), then adequate Cu atom diffusion for bonding is achieved, but processing time increases due to involvement of CMP processes
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures (>400°C) to low temperatures (250°C or less) and modifies the surface structure with nanograin layers, enabling diffusion bonding to proceed faster without requiring time-consuming CMP processes
Solution Approach 2:
The patent extracts and eliminates the CMP process from the conventional bonding sequence by replacing it with preliminary nanograin layer formation, thereby removing the time-consuming intermediate step while maintaining bonding quality
3Reliability
If conventional Cu—Cu direct welding is performed at high temperatures (above 400°C), then bonding is achieved, but energy consumption increases
Solution Approach 1:
The patent changes the temperature parameter from high (>400°C) to low (250°C or less), directly reducing the thermal energy input required for diffusion bonding while maintaining effective bonding through the introduced nanograin surface structure
4Reliability
If conventional Cu—Cu direct welding is performed, then bonding is achieved, but additional CMP processes are required which increase manufacturing cost
Solution Approach 1:
The patent changes the surface structure parameter by introducing nanograin layers and reduces the temperature parameter to 250°C or less, enabling bonding without CMP processes and thereby reducing manufacturing costs associated with equipment usage, materials, and labor
Solution Approach 2:
The patent extracts and eliminates the CMP process from the manufacturing sequence by replacing it with nanograin layer formation, removing the associated costs of CMP equipment, consumables, and processing time
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves high-quality Cu—Cu bonding with reduced energy requirements, faster processing times, and improved interface grain growth, minimizing electrical resistance and eliminating the need for costly and time-consuming CMP processes, thus revolutionizing IC packaging for 5G technology.
Implementation Method 1
Cu—Cu direct welding requires higher temperatures to adequately diffuse Cu atoms for bonding
Implementation Method 2
involving compressing a first copper structure with a second copper structure under a stress from 0.1 MPa to 50 MPa
Data Source
AI summary
Disclosed is a method of bonding two copper structures involving compressing a first copper structure with a second copper structure under a stress from 0.1 MPa to 50 MPa and under a temperature of 250° C. or less so that a bonding surface of the first copper structure is bonded to a bonding surface of the second copper structure; at least one of the bonding surface of the first copper structure and the bonding surface of the second copper structure have a layer of nanograins of copper having an average grain size of 5 nm to 500 nm, the layer of the nanograins of copper having a thickness of 10 nm to 10 μm.