SiC Power Device Metal Interconnect Layers
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Solution Overview
Problem
Conventional power semiconductor devices using Al-based materials for interconnection suffer from reactions with semiconductor regions and strain due to thermal expansion coefficient mismatches, particularly at high temperatures, affecting reliability.
Innovation Solution
A power semiconductor device structure incorporating a first metal layer with low reactivity metals like Pt, Ti, Mo, or W, and a second metal layer with low reactivity metals like Mo, W, or Cu, which reduces reactions and strain by acting as an interconnect metal, with a third metal layer of Pt, Mo, or W to prevent oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Al-based material is used as interconnection metal, then electrical conductivity is improved, but reaction with semiconductor region and oxidation occur at high temperature
Solution Approach 1:
The patent employs a composite metal interconnection structure consisting of multiple layers with different materials. The first metal layer contains Al-based material for electrical conductivity, while the second metal layer contains Cu-based material with different thermal expansion properties. This composite structure resolves the contradiction by combining materials that individually address different requirements (conductivity vs. thermal stability).
Solution Approach 2:
The patent introduces a barrier metal layer as an intermediary between the Al-based interconnection metal and the semiconductor region. This barrier layer prevents direct reaction between the Al-based material and the semiconductor, thereby maintaining reliability while preserving the electrical conductivity benefits of Al-based materials.
2Reliability
If Cu-based material is used as interconnection metal, then reactivity with semiconductor region is reduced, but thermal expansion mismatch causes strain
Solution Approach 1:
The patent creates a composite metal interconnection structure where the first metal layer contains Cu-based material to reduce reactivity with the semiconductor region, while the second metal layer contains Al-based material optimized for thermal expansion matching. This multi-layer composite approach resolves the contradiction by distributing different material properties across layers.
Solution Approach 2:
The patent applies different material properties to different locations (layers) of the interconnection structure. The Cu-based layer is positioned where reaction resistance is critical, while the Al-based layer is positioned where thermal expansion matching is critical. This local optimization resolves the contradiction by assigning specific material qualities to specific functional requirements.
3Ease of manufacture
If Al-based material is used for interconnection, then manufacturing process is simplified, but oxidation of metal surface occurs at high temperature
Solution Approach 1:
The patent employs a composite metal interconnection structure where the first metal layer contains Al-based material for ease of manufacture, while the second metal layer contains oxidation-resistant materials. This composite structure maintains the manufacturing advantages of Al-based materials while adding oxidation resistance through the second layer.
Solution Approach 2:
The patent introduces a protective metal layer as an intermediary between the Al-based interconnection material and the oxidizing environment. This barrier layer prevents oxidation of the Al-based material while allowing the manufacturing process to retain the simplicity advantages of using Al-based materials.
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 device is less prone to reactions and strain during high-temperature operation, enhancing reliability by using low reactivity metals that match thermal expansion coefficients and prevent oxidation.
Implementation Method 1
the first metal layer containing at least one selected from the group consisting of Pt, Ti, Mo, W and Ta... prevents the phenomenon of the incorporation of other metal species into the electrode even during high-temperature operation
Implementation Method 2
the thermal expansion coefficient of Cu is 17×10−6 K−1, and this value is significantly different from those of semiconductor materials such as Si (having a thermal expansion coefficient of 4.2×10−6 K−1) and SiC (having a thermal expansion coefficient of 3.7×10−6 K−1)... causes a strain in the power devices during high-temperature operation
Implementation Method 3
to cause oxidation of the surface of the metal material, thereby degrading the reliability of the device
Data Source
AI summary
A power semiconductor device less prone to cause a reaction between a metal material for interconnection and an electrode or the like connected to a semiconductor region during the high-temperature operation thereof and less prone to be strained during the high-temperature operation thereof. The power semiconductor device can be an SiC power device or the like in which a first metal layer containing at least one selected from the group consisting of Pt, Ti, Mo, W and Ta is formed on a source electrode formed on the semiconductor region, such as a source region or the like. A second metal layer containing at least one selected from the group consisting of Mo, W and Cu is formed on the first metal layer. A third metal layer containing at least one selected from the group consisting of Pt, Mo and W is formed on the second metal layer.