SiC Semiconductor Element Impurity Gradient for Saturation Current
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Solution Overview
Problem
Silicon carbide (SiC) power semiconductor devices face challenges in increasing saturation current during on-time, especially when used in large current driving circuits, due to limitations in diode function integration within the channel portion, which leads to potential crystal deterioration and reduced switching speed.
Innovation Solution
A semiconductor element design featuring a multilayered structure with specific impurity concentration gradients in the body and channel regions, allowing for increased saturation current without compromising diode characteristics, by optimizing the impurity concentration distribution in the silicon carbide semiconductor layers and body regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a pn-junction body diode is used as a freewheeling diode in SiC-FET, then the number of external parts can be reduced, but crystal deterioration occurs due to stacking faults increase from bipolar operation
Solution Approach 1:
The body region is divided into a first body region with higher impurity concentration and a second body region with lower impurity concentration. This segmentation allows the first body region to handle forward current while the second body region maintains lower noise and prevents stacking faults, thus resolving the contradiction between reducing external parts and preventing crystal deterioration.
2Productivity
If impurity concentration in the channel layer is increased to increase saturation current, then on-state current increases, but diode characteristics deteriorate
Solution Approach 1:
Different regions of the channel layer are assigned different impurity concentrations: the first channel layer has higher impurity concentration to increase saturation current, while the second channel layer has lower impurity concentration to maintain good diode characteristics. This local quality differentiation resolves the contradiction between increasing productivity and maintaining reliability.
3Ease of manufacture
If a single-layer channel structure is used, then manufacturing is simpler, but saturation current is limited and cannot support large current driving circuits
Solution Approach 1:
The channel structure is extended from a single layer to multiple layers with different impurity concentrations. This dimensional change in the vertical direction allows the device to achieve higher saturation current suitable for large current driving circuits while maintaining manufacturability through sequential layer formation processes.
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 enhances saturation current during on-time, enabling larger current flow while maintaining diode characteristics, reducing crystal deterioration, and allowing for the omission of external freewheeling diodes in inverter circuits, thus reducing the number of circuit components.
Implementation Method 1
the body region of the second conductivity type includes a first body region in contact with a surface of the first silicon carbide semiconductor layer, and a second body region in contact with a bottom surface of the body region of the second conductivity type, and an impurity concentration of the first body region is twice or more an impurity concentration of the second body region
Data Source
AI summary
In a semiconductor element, a body region of a second conductivity type includes a first body region in contact with a surface of a first silicon carbide semiconductor layer, and a second body region in contact with a bottom surface of the body region of the second conductivity type. The impurity concentration of the first body region is twice or more the impurity concentration of the second body region. A second silicon carbide semiconductor layer of a first conductivity type, which is a channel layer, has an impurity concentration distribution in a direction perpendicular to a semiconductor substrate, and an impurity concentration on a side in contact with the gate insulating film is lower than an impurity concentration on a side in contact with the first body region.