Semiconductor Metallization Sacrificial Protection Layer
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Solution Overview
Problem
Semiconductor devices face corrosion issues due to moisture, which can lead to failure, especially in aluminum-based front side metallizations where corrosion can spread and compromise the active semiconductor region, and existing passivation layers may crack under thermal stress, reducing their effectiveness.
Innovation Solution
A protection layer made of a less noble metal, such as aluminum, is deposited over the metallization layer to act as a sacrificial layer, preventing corrosion from penetrating to the active semiconductor region and withstanding thermal expansion without cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation layer is used to protect the metallization layer, then corrosion protection is improved, but the passivation layer may crack under thermal stress reducing its effectiveness
Solution Approach 1:
The protection system is segmented into multiple functional layers: a flexible underlayer (first metal layer) directly on the metallization, and a corrosion-resistant top layer (second metal layer). This segmentation allows each layer to specialize - the underlayer handles thermal stress through flexibility while the top layer provides corrosion protection, resolving the contradiction between protection and structural stability.
Solution Approach 2:
The invention uses a composite structure combining different metal materials with complementary properties. The first metal layer (e.g., aluminum or aluminum alloy) provides flexibility and thermal stress resistance, while the second metal layer (e.g., nickel or palladium) provides superior corrosion resistance. This composite approach allows the system to simultaneously achieve both corrosion protection and thermal stability that neither material could provide alone.
2Ease of manufacture
If the metallization layer is made of aluminum or aluminum alloy, then electrical conductivity and ease of manufacture are improved, but corrosion resistance deteriorates allowing corrosion to spread to the active semiconductor region
Solution Approach 1:
The second metal layer acts as an intermediary barrier between the aluminum-based metallization layer and the corrosive environment. This intermediate layer prevents direct contact between corrosive substances and the aluminum, stopping corrosion propagation while allowing the aluminum layer to maintain its electrical and manufacturing advantages. The intermediary layer effectively decouples the contradiction between ease of manufacture and corrosion resistance.
Solution Approach 2:
By creating a composite metallization structure with aluminum (or aluminum alloy) as the base layer and a more corrosion-resistant metal as the top layer, the system combines the manufacturing ease and electrical properties of aluminum with the corrosion resistance of the second metal. This composite approach resolves the contradiction by allowing each material to contribute its strengths without compromising the other.
3Reliability
If a protection layer is added to prevent corrosion, then reliability is improved, but device complexity increases
Solution Approach 1:
The invention extracts the corrosion protection function from the single passivation layer concept and places it in a dedicated top metal layer, while the underlying metal structure handles electrical and mechanical functions. This functional extraction allows for more effective corrosion protection without significantly increasing overall device complexity, as the additional layer integrates seamlessly with existing metallization processes.
Solution Approach 2:
The multi-layer metal structure serves multiple functions simultaneously: the first metal layer provides electrical connectivity and thermal stress management, while the second metal layer provides corrosion protection. This multi-functionality reduces the need for separate dedicated protection components, thereby limiting the increase in device complexity while achieving improved reliability.
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 significantly extends the lifespan of the semiconductor device by preventing corrosion and maintaining structural integrity under thermal stress, as demonstrated by a 500 nm aluminum layer extending the H3TRB test duration from 700-800 hours to 1500 hours.
Implementation Method 1
A protection layer made of a less noble metal, such as aluminum, is deposited over the metallization layer to act as a sacrificial layer, preventing corrosion from penetrating to the active semiconductor region
Implementation Method 2
withstanding thermal expansion without cracking
Data Source
AI summary
According to various embodiments, a semiconductor device may include: a layer stack formed at a surface of the semiconductor device, the layer stack including: a metallization layer including a first metal or metal alloy; a protection layer covering the metallization layer, the protection layer including a second metal or metal alloy, wherein the second metal or metal alloy is less noble than the first metal or metal alloy.