SiC Super Junction Pillar Boundary for High-Voltage Reliability
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Solution Overview
Problem
SiC power devices face challenges in maintaining high breakdown voltage and reliability due to defects at the boundary between n-type and p-type pillars, which are prone to strong electric fields during depletion layer spreading.
Innovation Solution
Incorporating a boundary region with a lower and constant impurity concentration between n-type and p-type pillars in a super junction structure, which mitigates electric field stress on defects and enhances reliability for high voltage applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a super junction structure with p-type and n-type pillars is used to achieve low on-resistance and high breakdown voltage, then the on-resistance decreases and breakdown voltage increases, but defects at the boundary between pillars cause reduced reliability under high voltage conditions
Solution Approach 1:
An intermediate layer with intermediate impurity concentration is introduced between the high impurity concentration region and the low impurity concentration region. This intermediate layer acts as a mediator that gradually transitions the impurity concentration, thereby reducing the abrupt change in electric field strength and minimizing the stress on defects at the boundary between p-type and n-type pillars.
Solution Approach 2:
The impurity concentration parameter is changed gradually across multiple regions rather than abruptly. By creating a gradient in impurity concentration (high concentration region → intermediate concentration region → low concentration region), the electric field distribution is optimized to reduce peak field strength at defect locations while maintaining the overall super junction structure's low on-resistance and high breakdown voltage characteristics.
2Reliability
If the impurity concentration is set high in the drift region to maintain breakdown voltage, then the breakdown voltage is maintained, but the on-resistance increases
Solution Approach 1:
Different regions of the drift region are assigned different impurity concentrations based on their local requirements. The region near the junction uses high impurity concentration to maintain breakdown voltage, while the region farther from the junction uses low impurity concentration to minimize on-resistance. The intermediate concentration region provides a smooth transition between these two extremes, optimizing both parameters locally.
Solution Approach 2:
The drift region is segmented into multiple regions with different impurity concentrations: a high concentration region, an intermediate concentration region, and a low concentration region. This segmentation allows each region to contribute differently to the overall device performance, with the high concentration region supporting breakdown voltage and the low concentration region reducing on-resistance, while the intermediate region provides a smooth transition.
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
The boundary region design improves the breakdown voltage and reliability of SiC semiconductor devices by reducing electric field stress on defects, ensuring consistent performance under high voltage conditions.
Implementation Method 1
the boundary region having a lower impurity concentration than the n-type pillars and the p-type pillars
Implementation Method 2
which are prone to strong electric fields during depletion layer spreading
Data Source
AI summary
The super junction structure part includes a plurality of n-type pillars having higher impurity concentrations than the second layer, a plurality of p-type pillars having higher impurity concentrations than the second layer, and a boundary region positioned between the n-type pillar and the p-type pillar in a second direction orthogonal to the first direction, the boundary region extending in the first direction continuously from the second layer, the boundary region having a lower impurity concentration than the n-type pillars and the p-type pillars.