IGBT Emitter Interface Layer Reduces Reverse Recovery Losses
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Solution Overview
Problem
RC-IGBTs experience high switching losses due to permanent changes between reverse and forward biased states in applications like motor drivers and switched mode power supplies, which is not effectively addressed by existing technologies.
Innovation Solution
The design includes a semiconductor portion with IGBT cells featuring a source zone, body zone, and drift zone, along with an emitter electrode having a main layer and an interface layer with higher contact resistance than the main layer, utilizing materials like titanium and tungsten in the interface layer to reduce contact resistance and diode hole emitter efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a low contact resistance is used between the emitter electrode and the body zone, then good electrical connection is achieved, but reverse recovery losses increase
Solution Approach 1:
The patent applies local quality by creating different contact resistance characteristics in different regions of the emitter electrode. The interface layer is selectively positioned to contact the body zone while maintaining different contact resistance values in different areas, allowing low contact resistance where good electrical connection is needed and high contact resistance where reverse recovery loss reduction is prioritized.
Solution Approach 2:
The emitter electrode uses a composite structure with multiple layers including an interface layer with specific material composition. This composite material approach allows the electrode to exhibit different electrical properties in different regions, combining the benefits of low contact resistance for reliable connection with high contact resistance for reducing reverse recovery losses.
2Productivity
If the interface layer contact resistance is increased to reduce diode hole emitter efficiency, then switching losses are reduced, but contact quality may deteriorate
Solution Approach 1:
The interface layer is strategically positioned to contact specific regions of the body zone, creating local variations in contact resistance. This allows the structure to achieve high switching speed where increased contact resistance is beneficial while maintaining good contact quality in regions where the interface layer does not directly contact the body zone.
Solution Approach 2:
The interface layer acts as an intermediary between the emitter electrode and the body zone, mediating the contact resistance characteristics. By controlling the interface layer's material composition and positioning, the patent achieves the desired balance between switching performance and contact quality without direct contact between the emitter electrode and body zone.
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 approach significantly reduces reverse recovery losses without compromising voltage blocking capabilities or device ruggedness, allowing for faster switching and improved performance in RC-IGBTs.
Implementation Method 1
A contact resistance between the semiconductor portion and the interface layer is higher than between the semiconductor portion and a material of the main layer
Implementation Method 2
utilizing materials like titanium and tungsten in the interface layer to reduce contact resistance and diode hole emitter efficiency
Data Source
AI summary
An IGBT includes a semiconductor portion with IGBT cells. Each IGBT cell includes a source zone of a first conductivity type, a body zone of a second, complementary conductivity type, and a drift zone of the first conductivity type separated from the source zone by the body zone. An emitter electrode includes a main layer and an interface layer. The interface layer directly adjoins at least one of the body zone and a supplementary zone of the second conductivity type. A contact resistance between the semiconductor portion and the interface layer is higher than between the semiconductor portion and a material of the main layer. For example, the interface layer may reduce diode emitter efficiency and reverse recovery losses in IGBTs.