Diamond-Metal Composite Substrate for Low-Stress Insulating Bonding
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Solution Overview
Problem
Existing composite substrates for semiconductor devices face challenges in achieving high thermal conductivity and reliable bonding due to differences in thermal expansion coefficients and surface roughness, which can lead to detachment and reduced heat dissipation efficiency.
Innovation Solution
A composite substrate with a base layer of diamond and metal, a flat layer with a surface roughness of 10 nm or less, and an insulating layer directly bonded to the substrate, using techniques like atomic diffusion bonding to ensure strong bonding without intentional heating, allowing for effective heat dissipation and electrical insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If diamond particles are dispersed in metal to create composite substrate, then thermal conductivity is improved, but bonding reliability deteriorates due to detachment caused by thermal expansion coefficient differences
Solution Approach 1:
An intermediate layer is introduced between the diamond particle-containing base layer and the insulating layer. This intermediate layer has a thermal expansion coefficient positioned between those of the base layer and insulating layer, acting as a buffer to reduce thermal expansion mismatch stress and prevent detachment, while maintaining effective heat dissipation pathways.
Solution Approach 2:
The thermal expansion coefficient of the intermediate layer is specifically selected to be between the thermal expansion coefficients of the base layer and insulating layer. This parameter optimization creates a gradient structure that progressively accommodates thermal expansion differences, reducing stress concentration and improving bonding reliability without compromising thermal conductivity.
2Ease of manufacture
If conventional bonding methods are used between insulating layer and substrate, then bonding process is simplified, but bonding strength deteriorates due to surface roughness
Solution Approach 1:
The surface of the base layer is preliminarily processed to achieve a specific roughness range (0.3-3 μm) before bonding. This preliminary surface preparation creates optimal bonding conditions that enhance adhesion strength while maintaining process simplicity, avoiding the need for complex bonding procedures.
Solution Approach 2:
The surface roughness parameter is optimized to a specific range (0.3-3 μm) that balances bonding strength and manufacturing ease. This parameter optimization ensures sufficient surface area and mechanical interlocking for strong bonding while remaining achievable through conventional surface processing methods.
3Strength
If flat layer with Ra ≤ 10 nm is created for direct bonding, then bonding strength is improved, but manufacturing complexity increases
Solution Approach 1:
An intermediate layer with moderate surface roughness (0.3-3 μm) is introduced as a mediator between the base layer and insulating layer. This intermediate layer provides sufficient bonding strength through its optimized roughness while avoiding the need for ultra-precision flatening processes, thereby reducing manufacturing complexity.
Solution Approach 2:
Different surface roughness characteristics are applied to different layers: the intermediate layer has moderate roughness (0.3-3 μm) for optimal bonding, while the flat layer has ultra-fine roughness (Ra ≤ 10 nm) for direct bonding capability. This localized quality differentiation optimizes bonding strength at each interface without requiring all surfaces to meet the highest precision standards.
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
The solution enhances thermal conductivity and bonding strength, reducing thermal resistance and ensuring reliable heat dissipation while maintaining electrical insulation, thus addressing the limitations of existing composite substrates.
Implementation Method 1
an insulating layer directly bonded to the upper surface of the flat layer
Implementation Method 2
a composite material comprising diamond and a metal has been under development. In such a composite material, particles of diamond, which has a higher thermal conductivity than those of metals, are dispersed in a metal such as copper (Cu)
Data Source
AI summary
A composite substrate includes a base layer formed of a composite material containing diamond and a metal, the base layer a first surface, and a second surface opposite to the first surface; a flat layer having a lower surface bonded to the first surface of the base layer, and an upper surface having a surface roughness Ra of 10 nm or less; and an insulating layer directly bonded to the upper surface of the flat layer.