SiC Diode Drift Region Doping for Stacking Fault Suppression
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Solution Overview
Problem
In silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs), the accumulation of holes in the n-type substrate leads to the extension of stacking faults, reducing current conductivity due to basal plane dislocations, which deteriorates electrical conduction in p-n diodes.
Innovation Solution
A diode with a semiconductor substrate featuring a drift region composed of alternately arranged p-type and n-type column regions, where the specific region within the drift region has a lower effective p-type impurity concentration and a higher effective n-type impurity concentration, capturing and recombining holes to reduce their accumulation in the n-type semiconductor region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If holes are allowed to flow freely through the drift region to the n-type substrate, then current conductivity is maintained, but hole accumulation in the n-type substrate causes stacking fault extension and deteriorates electrical conduction
Solution Approach 1:
The drift region is divided into alternating p-type column regions and n-type column regions with different impurity concentrations. The p-type column regions have higher impurity concentration to capture holes, while n-type column regions have lower impurity concentration to allow electron flow. This local differentiation of properties enables selective hole capture without blocking overall current conduction.
Solution Approach 2:
The patent changes the impurity concentration parameters in the drift region by creating columnar structures with alternating p-type and n-type regions. The p-type column regions have higher acceptor concentration to increase hole capture capability, while maintaining overall drift region functionality for current conduction.
2Reliability
If the drift region uses uniform impurity concentration, then manufacturing is simplified, but hole capture efficiency is insufficient leading to stacking fault extension
Solution Approach 1:
The drift region is segmented into multiple vertical columnar structures alternating between p-type and n-type regions. This segmentation allows different functional zones within the drift region - p-type columns for hole capture and n-type columns for maintaining electron conductivity - thereby suppressing stacking faults while managing structural complexity.
Solution Approach 2:
Different regions of the drift region are given different impurity concentrations and types (p-type vs n-type columns) to perform different functions. The p-type column regions locally concentrate hole capture capability, while n-type regions maintain overall conductivity, achieving stacking fault suppression through localized property differentiation.
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 effectively reduces the number of holes reaching the n-type semiconductor region, thereby suppressing the deterioration in electrical conduction and minimizing the extension of stacking faults, enhancing the diode's current conductivity.
Implementation Method 1
The plurality of p-type column regions has an effective p-type impurity concentration that is lower in the specific region than in a region on a periphery of the specific region, and the plurality of n-type column regions has an effective n-type impurity concentration that is higher in the specific region than in a region on a periphery of the specific region
Data Source
AI summary
A diode has a semiconductor substrate made of silicon carbide. The semiconductor substrate includes a p-type first semiconductor region, a drift region below the first semiconductor region, and an n-type second semiconductor region below the drift region. The drift region has a plurality of p-type column regions and a plurality of n-type column regions alternately arranged in a lateral direction. The drift region includes a specific region distributed over the plurality of p-type column regions and the plurality of n-type column regions, at least at a part in a depth direction. The plurality of p-type column regions has an effective p-type impurity concentration that is lower in the specific region than in a portion around the specific region, and the plurality of n-type column regions has an effective n-type impurity concentration that is higher in the specific region than in a portion around the specific region.