SiC Super Junction MOSFET Edge Termination for Higher Breakdown Voltage
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Solution Overview
Problem
Conventional silicon carbide MOSFETs with a super junction structure exhibit lower breakdown voltage in the edge termination region compared to the active region, leading to reduced breakdown tolerance due to avalanche breakdown occurring easily in the edge termination region.
Innovation Solution
The silicon carbide semiconductor device incorporates a parallel pn layer with first and second conductivity-type column regions alternating in the active and termination regions, featuring second-conductivity-type high-concentration regions and a voltage withstand structure to enhance breakdown voltage, shifting the avalanche breakdown location to the active region with a larger surface area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional super junction structure is used in the edge termination region, then the device can be manufactured with standard processes, but the breakdown voltage in the edge termination region is lower than in the active region, reducing overall breakdown tolerance
Solution Approach 1:
The patent applies different SJ structure configurations to different regions: the active region uses a standard SJ structure with alternating n-type and p-type column regions, while the edge termination region uses a modified SJ structure with adjusted column region dimensions and impurity concentrations. This local differentiation allows the edge termination region to achieve higher breakdown voltage while maintaining compatibility with standard manufacturing processes used in the active region.
Solution Approach 2:
The patent modifies key parameters of the SJ structure in the edge termination region, including the width and depth of column regions, impurity concentration distributions, and the arrangement pattern of alternating n-type and p-type regions. These parameter changes are specifically optimized to elevate the breakdown voltage in the edge termination region to match or exceed that of the active region, thereby improving overall device reliability.
2Reliability
If the breakdown voltage of the edge termination region is increased to match the active region, then avalanche breakdown will occur in the active region with larger surface area, but this requires modifying the SJ structure in the termination region which increases device complexity
Solution Approach 1:
The patent designs the SJ structure in the edge termination region to serve multiple functions: it maintains the voltage blocking capability required for high breakdown voltage, while also being compatible with the standard fabrication processes used for the active region. The modified column region configuration in the termination region achieves both elevated breakdown voltage and process integration, reducing the need for separate complex manufacturing steps.
Solution Approach 2:
The patent divides the semiconductor device into distinct functional regions with optimized SJ structures: the active region maintains standard SJ configuration for current conduction, while the edge termination region employs a segmented pattern of modified n-type and p-type column regions specifically designed for voltage blocking. This segmentation allows each region to be optimized for its specific function while maintaining overall device integrity and manageable complexity.
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 increases the breakdown tolerance by elevating the breakdown voltage of the edge termination region, ensuring avalanche breakdown occurs in the active region, thus enhancing the overall device's performance.
Implementation Method 1
a parallel pn layer is provided in the semiconductor substrate, in the active region and the termination region. The parallel pn layer has first-conductivity-type column regions and second-conductivity-type column regions disposed repeatedly alternating with one another
Implementation Method 2
second-conductivity-type high-concentration regions are selectively provided between the first semiconductor region and the parallel pn layer in the active region and the termination region
Data Source
AI summary
In an active region and an edge termination region, a drift layer is constituted by a same SJ structure with a parallel pn layer. In the edge termination region, a p+-type extension portion between the active region and a JTE structure fixes the JTE structure to the potential of a source electrode. The p+-type extension portion is between and in contact with a p-type base extension portion and the parallel pn layer. The p+-type extension portion is an extension of upper portions of p+-type regions provided in the active region to mitigate electric field near bottoms of gate trenches. Between the p-type base extension portion and the parallel pn layer is free of the lower portions of the p+-type regions. Thus, a length in the depth direction of the p-type column regions of the edge termination region is longer than that of the p-type column regions of the active region.