Alternating Metal Interconnects for Wide-Bandgap Semiconductor Reliability
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Solution Overview
Problem
High-power semiconductor devices with wide bandgap materials face interconnect failure due to thermal stresses and metallurgical issues, such as delamination and corrosion, caused by the mismatch in coefficients of thermal expansion between different metal layers used in conventional metal interconnect systems.
Innovation Solution
A metal interconnect structure with alternating diffusion barrier layers and high electrical conductivity layers, where the diffusion barrier layers have a lower coefficient of thermal expansion than the conductivity layers, constraining their expansion to prevent excessive strain and maintain bond strength between layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal interconnect systems with multiple metal layers are used to achieve high electrical conductivity, then electrical conductivity is improved, but thermal expansion mismatch causes delamination and corrosion under high power operation
Solution Approach 1:
The interconnect structure is divided into multiple alternating layers of diffusion barrier metal and high conductivity metal, creating a segmented composite structure that manages thermal expansion differently than conventional single-material interconnects
Solution Approach 2:
The patent uses composite material structure with alternating layers of diffusion barrier metal (e.g., molybdenum, tungsten) and high conductivity metal (e.g., gold, aluminum), where each material contributes its superior properties while the composite structure manages thermal stress
2Power
If high power density operation is implemented to increase device output, then power output is improved, but interconnect failure occurs earlier due to thermal stresses
Solution Approach 1:
The patent changes the physical parameters of the interconnect structure by using alternating layers with different thermal expansion coefficients, allowing the structure to withstand higher power density operation without premature failure
Solution Approach 2:
The diffusion barrier layers are placed beforehand to constrain thermal expansion of the high conductivity layers, providing protective cushioning against thermal stresses before they can cause delamination or corrosion
3Strength
If diffusion barrier metal layers are added to prevent metallurgical reactions, then adhesion and barrier properties are improved, but coefficient of thermal expansion mismatch increases thermal stress
Solution Approach 1:
Within each functional layer type, the patent maintains material homogeneity while alternating between different material types, creating a structured composite that balances adhesion needs with thermal stress management
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 effectively enhances the thermal stability and reliability of high-power semiconductor devices by reducing thermo-mechanical stress, preventing delamination and corrosion, and extending the operational life of devices like MESFETs and HEMTs beyond conventional limits.
Implementation Method 1
The diffusion barrier layers have a coefficient of thermal expansion different from and lower than the coefficient of thermal expansion of the high electrical conductivity layers. The difference in the respective coefficients of thermal expansions is large enough to constrain the expansion of the high conductivity layers
Data Source
AI summary
A semiconductor device structure is disclosed that includes a wide-bandgap semiconductor portion selected from the group consisting of silicon carbide and the Group III nitrides. An interconnect structure is made to the semiconductor portion, and the interconnect structure includes at least two diffusion barrier layers alternating with two respective high electrical conductivity layers. The diffusion barrier layers have a coefficient of thermal expansion different from and lower than the coefficient of thermal expansion of the high electrical conductivity layers. The difference in the respective coefficients of thermal expansions are large enough to constrain the expansion of the high conductivity layers but less than a difference that would create a strain between adjacent layers that would exceed the bond strength between the layers.