Semiconductor Layer Structure to Suppress Avalanche Secondary Breakdown
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Solution Overview
Problem
Avalanche breakdown in semiconductor devices for power control can lead to parasitic n-p-n transistor turn-on and secondary breakdown, compromising device reliability.
Innovation Solution
The semiconductor device incorporates a second base layer with a higher carrier concentration than the first base layer, positioned further towards the first electrode side, and a trench contact with a lower end positioned below the first base layer's surface, which directs the hole current away from the first base layer, preventing parasitic n-p-n transistor activation and secondary breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If avalanche breakdown occurs in the semiconductor device, then high breakdown voltage is achieved, but parasitic n-p-n transistor turns on causing secondary breakdown
Solution Approach 1:
The base layer is segmented into a first base layer and a second base layer with different carrier concentrations. The second base layer has a higher carrier concentration than the first base layer, creating distinct regions that control hole current flow differently. This segmentation allows the device to achieve high breakdown voltage while preventing parasitic transistor activation through the second base layer's superior hole collection capability.
Solution Approach 2:
Different regions of the base layer are given different local qualities through varying carrier concentrations. The second base layer positioned near the drift layer has higher carrier concentration to efficiently collect holes at the avalanche breakdown site, while the first base layer has lower carrier concentration. This local quality differentiation enables simultaneous achievement of high breakdown voltage and reliability by controlling where and how holes are collected.
2Ease of manufacture
If the trench contact lower end is positioned close to the insulating body, then manufacturing simplicity is maintained, but hole current flows into the first base layer activating parasitic transistor
Solution Approach 1:
The second base layer acts as an intermediary between the drift layer and the first base layer. It has higher carrier concentration than the first base layer, which enables it to effectively intercept and collect holes before they can reach the first base layer. This intermediary structure with optimized carrier concentration prevents parasitic transistor activation while maintaining a simple trench contact configuration that extends to the first base layer.
3Reliability
If the second base layer has higher carrier concentration, then hole current is directed away from the first base layer, but device complexity increases
Solution Approach 1:
The base layer is divided into two segments: a first base layer with lower carrier concentration and a second base layer with higher carrier concentration. This segmentation creates a functional gradient where the second base layer preferentially collects holes due to its higher carrier concentration, directing hole current away from the first base layer and preventing parasitic transistor activation. The segmented structure achieves reliable parasitic transistor suppression through controlled carrier concentration distribution.
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 enhances the reliability of the semiconductor device by suppressing secondary breakdown and maintaining high breakdown voltage, allowing for high-speed operation with reduced output capacitance and reverse transfer capacitance.
Implementation Method 1
When avalanche breakdown occurs in a semiconductor device for power control, there are cases where a parasitic n-p-n bipolar transistor turns on, and secondary breakdown occurs
Data Source
AI summary
A semiconductor device includes a first electrode, a second electrode, a first semiconductor layer, a third electrode, a second semiconductor layer, a third semiconductor layer, a fourth electrode, and a fourth semiconductor layer. The third semiconductor layer extends from the second semiconductor layer toward the first electrode side. A lower end of the third semiconductor layer at the first electrode side is positioned further toward the first electrode side than the lower surface of the second semiconductor layer and is separated from the insulating body. The third semiconductor layer is of the second conductivity type. The fourth electrode faces the second semiconductor layer via an other portion of the insulating body. The fourth semiconductor layer is located between the second semiconductor layer and the second electrode and electrically connected with the second electrode. The fourth semiconductor layer is of the first conductivity type.