Al-based Electrode Structure for Semiconductor Devices
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Solution Overview
Problem
Conventional semiconductor devices with Al-based electrodes face issues such as erosion of Si substrates during electroless plating due to alkaline-based agents and increased forward voltage due to barrier metals, leading to contact resistance and potential damage to the semiconductor layer.
Innovation Solution
A semiconductor device structure with a first Al-based electrode, a barrier metal, and a second Al-based electrode, where the second electrode is thicker and has fine irregularities, and a plated layer is formed using electroless plating, with the barrier metal preventing the alkaline-based agent from reaching the semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a barrier metal is provided between the Al-based electrode and the Si substrate, then the Si substrate is protected from erosion by the alkaline-based agent, but the forward voltage increases due to the barrier effect
Solution Approach 1:
The electrode structure is segmented into multiple layers: a first Al-based electrode layer in direct contact with the Si substrate, a second Al-based electrode layer above it, and a plated layer on the second Al-based electrode. This segmentation allows the first Al-based electrode to protect the Si substrate while the second Al-based electrode and plated layer provide the necessary electrical connection with low forward voltage, eliminating the need for a barrier metal that would increase forward voltage.
Solution Approach 2:
The first Al-based electrode layer acts as an intermediary between the Si substrate and the second Al-based electrode layer. It provides the barrier function to protect the Si substrate from the alkaline-based agent during electroless plating, while allowing the second Al-based electrode and plated layer to maintain low contact resistance and forward voltage through direct contact with the semiconductor layer.
2Strength
If the Al-based electrode is annealed to improve adhesion, then adhesion is improved, but hillocks are generated on the Al surface due to plastic deformation
Solution Approach 1:
The Al-based electrode is divided into a first Al-based electrode layer and a second Al-based electrode layer. The first layer is annealed to improve adhesion to the Si substrate, while the second layer remains relatively free of hillocks and provides the surface for electroless plating. This segmentation isolates the hillock formation to the first layer, preventing it from affecting the plating process.
3Reliability
If the second Al-based electrode is made thicker to reduce contact resistance, then contact resistance is reduced, but the electrode structure becomes more complex
Solution Approach 1:
The second Al-based electrode layer serves multiple functions: it provides a thick, low-resistance electrical connection to the semiconductor layer, serves as a substrate for the plated layer, and acts as a barrier to prevent the alkaline-based agent from reaching the first Al-based electrode layer. This multi-functionality reduces the need for additional layers, simplifying the overall structure while maintaining low contact resistance.
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 configuration reduces contact resistance and prevents semiconductor layer damage during electroless plating, while maintaining low forward voltage by blocking the alkaline-based agent and minimizing stress-induced hillocks and cavities.
Implementation Method 1
a barrier metal between the first Al-based electrode and the second Al-based electrode... blocking the alkaline-based agent
Implementation Method 2
forming a plated layer on the second Al-based electrode by electroless plating
Implementation Method 3
Al is subjected to plastic deformation due to the difference of a linear expansion coefficient between Al and Si and hillocks are easily generated on the Al surface
Implementation Method 4
Al is subjected to plastic deformation due to the difference of a linear expansion coefficient between Al and Si
Implementation Method 5
when the Al contracts by being cooled, cavities and spaces are likely to be formed in a grain boundary under the hillocks
Data Source
AI summary
A semiconductor device according to the present invention includes: a semiconductor layer including a first conductivity type semiconductor region and a second conductivity type semiconductor region joined to the first conductivity type semiconductor region; and a surface electrode connected to the second conductivity type region on one surface of the semiconductor layer, including a first Al-based electrode, a second Al-based electrode, a barrier metal interposed between the first Al-based electrode and the second Al-based electrode, and a plated layer on the second Al-based electrode.