Corrosion-Resistant Metallization for Semiconductor Edge Termination
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Solution Overview
Problem
Semiconductor devices face corrosion issues in high-voltage edge termination areas due to moisture penetration, leading to potential failure, especially in humid environments, as evidenced by tests like the H3TRB, where metal structures in Al-alloys can corrode, forming stress-induced cracks in the passivation layer.
Innovation Solution
The use of a semiconductor device design where a first metal layer made of an electrochemically more stable material, such as TiW or WTi, extends laterally further towards the outer rim than a second metal layer, typically Al or Al-alloy, in the edge termination area, with an insulating passivation covering the first metal layer and exposing the second metal layer in the active area, enhancing corrosion resistance and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Al-alloy metal structures are used in edge termination areas, then electrical conductivity and cost are improved, but corrosion resistance deteriorates due to electro-galvanic cells formed by Si and Cu segregations
Solution Approach 1:
The patent applies different metal materials to different regions: a first metal material (Al-alloy) is used in the active area where conductivity is critical, while a second metal material (electrochemically stable material) is used in the edge termination area where corrosion resistance is critical. This local differentiation resolves the contradiction by optimizing each region for its specific functional requirements.
Solution Approach 2:
The patent uses a composite metallization structure combining two different metal materials in a layered configuration. The first metal layer (Al-alloy) provides conductivity in the active area, while the second metal layer (electrochemically stable material) provides corrosion resistance in the edge termination area, creating a composite structure that achieves both conductivity and corrosion resistance simultaneously.
2Reliability
If passivation is applied to protect metal structures, then moisture protection is improved, but stress-induced cracks may form due to volume expansion of corrosion products
Solution Approach 1:
The patent prevents corrosion before it can occur by using an electrochemically stable metal material in the edge termination area that is resistant to electro-galvanic corrosion. By eliminating the corrosion source beforehand, the passivation layer is protected from the damaging volume expansion forces that would otherwise cause stress-induced cracks, maintaining both protection and structural integrity.
3Adaptability or versatility
If metal structures extend to outer rim for electrical potential distribution, then field shaping capability is improved, but corrosion susceptibility increases in edge termination areas
Solution Approach 1:
The patent extends the metallization to the outer rim for field shaping purposes but applies different materials locally: the first metal material (Al-alloy) is used in the active area while the second metal material (electrochemically stable material) is used specifically in the edge termination area at the outer rim. This local differentiation allows the structure to achieve both field shaping capability and resistance to moisture penetration at the vulnerable edge regions.
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 design significantly reduces the risk of corrosion and mechanical-induced crack formation, improving the reliability of semiconductor devices by using electrochemically stable materials in the edge termination area and maintaining the blocking capabilities under high humidity and temperature conditions.
Implementation Method 1
The first metallic material is electrochemically more stable than the second metallic material
Implementation Method 2
Insulation of the metal structures is provided by a passivation. In addition to electrical insulation, the passivation also protects the semiconductor device against moisture and ionic contaminations
Implementation Method 3
corrosion in Al-alloys which include Si and Cu can be induced by local electro-galvanic cells formed by segregations of Si and Cu
Data Source
AI summary
A semiconductor device includes a semiconductor substrate having a first side, a second side opposite the first side, an active area, an outer rim, and an edge termination area arranged between the outer rim and the active area. A metallization structure is arranged on the first side of the semiconductor substrate and comprising at least a first metal layer comprised of a first metallic material and a second metal layer comprised of a second metallic material, wherein the first metallic material is electrochemically more stable than the second metallic material. The first metal layer extends laterally further towards the outer rim than the second metal layer.