SiC Semiconductor Device Segmented Termination for Breakdown Voltage
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Solution Overview
Problem
Silicon carbide semiconductor devices face challenges in achieving high breakdown voltage and reliability, particularly in high-temperature environments, due to limitations in avalanche resistance and termination region structures.
Innovation Solution
A silicon carbide semiconductor device design incorporating a silicon carbide substrate with specific impurity regions, an electric field relaxing region, and guard rings, along with a method of manufacturing that includes ion implantation and thermal oxidation, to enhance withstand capability by controlling impurity concentrations and electrode connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional termination region structure is used, then the device structure is simple, but the breakdown voltage is limited and avalanche resistance is poor
Solution Approach 1:
The termination region is segmented into multiple functional zones: a first termination region with higher impurity concentration for basic field control, a second termination region with lower impurity concentration for voltage blocking, and a third termination region with intermediate properties. This segmentation allows each region to perform its specific function optimally, achieving high breakdown voltage through progressive field relaxation across the segmented structure.
Solution Approach 2:
Different regions of the termination structure are given different local properties through controlled impurity concentrations. The first termination region has higher impurity concentration for strong field control near the junction, while the second termination region has lower impurity concentration for high voltage blocking capability. This local differentiation of properties enables the structure to simultaneously achieve both field control and high breakdown voltage.
2Reliability
If the impurity concentration is increased to improve field control, then the field control improves, but heat generation increases and reliability decreases
Solution Approach 1:
The impurity concentration is segmented across different termination regions rather than being uniformly high. The first termination region has higher impurity concentration for field control, while the second termination region has lower impurity concentration to reduce heat generation during avalanche breakdown. This segmentation allows field control to be achieved where needed without generating excessive heat throughout the entire termination region.
Solution Approach 2:
The impurity concentration is locally optimized in different regions: higher concentration in the first termination region where strong field control is needed, and lower concentration in the second termination region where heat generation must be minimized. This local quality differentiation enables effective field control while reducing harmful heat generation in regions where it is less critical.
3Ease of manufacture
If a simple termination structure is used, then the manufacturing process is simple, but the withstand capability and operational safety are reduced
Solution Approach 1:
The termination region is divided into three distinct zones with different impurity concentrations, each formed through controlled ion implantation processes. While this segmented structure increases manufacturing complexity compared to a simple single-region termination, it enables progressive electric field relaxation that significantly enhances breakdown voltage and avalanche resistance, providing the necessary withstand capability for high-voltage applications.
Solution Approach 2:
The impurity concentration parameter is changed across different termination regions to achieve optimal performance. By controlling the impurity concentration to decrease from the first to the second termination region, the structure achieves progressive field relaxation that enhances breakdown voltage. This parameter variation is implemented through controlled ion implantation processes that can precisely adjust concentration gradients.
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 design increases the semiconductor device's withstand capability by directing avalanche breakdown to regions with lower impurity concentrations, reducing heat generation and improving breakdown voltage, thus enhancing reliability and operational safety.
Implementation Method 1
forming an oxide film on the first main surface of the silicon carbide substrate by thermal oxidation of the silicon carbide substrate
Implementation Method 2
forming, in the first impurity region, by ion implantation, a second impurity region, a third impurity region, an electric field relaxing region, and at least one guard ring region
Data Source
AI summary
A silicon carbide semiconductor device includes: a drift layer in contact with a first main surface and having a first conductivity type; a body region located in the drift layer, in contact with the first main surface, and having a second conductivity type; and a protruding portion having the second conductivity type and connected to a bottom of the body region. A manufacturing method includes forming, in the drift layer of a silicon carbide substrate, by ion implantation, the body region, the protruding portion, a JTE region, and at least one guard ring region, each having the second conductivity type.