SiC Semiconductor Device Reflux Current Path Design
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Solution Overview
Problem
Conventional silicon carbide (SiC) power elements face challenges with reflux current flow when in an OFF state due to reduced current from source to drain, leading to potential degradation and increased stacking faults.
Innovation Solution
A semiconductor device design incorporating a first and second cell structure with specific silicon carbide semiconductor layers, ohmic electrodes, and insulating films, allowing independent control of the electric potential of the second silicon carbide semiconductor layer, which reduces the reduction in current flowing from source to drain when in an OFF state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative bias is applied to the gate to prevent false turn-on, then the power element is in an OFF state, but the current flowing from source to drain is reduced
Solution Approach 1:
The invention divides the semiconductor device into two independent cells: a first cell with a gate electrode for normal switching control, and a second cell without a gate electrode that serves as a dedicated reflux current path. This segmentation allows the second cell to maintain high current flow capability while the first cell provides reliable OFF state control, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The second cell structure serves multiple functions: it acts as a reflux current path during normal operation and can also function as an additional current path during high current demands. By making the overall device structure multi-functional, the invention maintains both reliable OFF state control and high current flow capability simultaneously.
2Reliability
If a Schottky diode is externally attached to allow reflux current flow, then the reflux current path is provided, but the number of members increases and device area increases
Solution Approach 1:
The invention merges the reflux current path function into the main semiconductor device structure by creating a second cell without a gate electrode. This integration eliminates the need for external Schottky diodes, reducing the number of components while maintaining the reflux current path functionality, thus resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The second cell serves as a multi-functional element that provides both the reflux current path and acts as part of the main power element structure. This universal design eliminates the need for separate external components, reducing device complexity while maintaining the necessary reflux current capability.
3Reliability
If the body diode is used as a reflux current path in SiC power elements, then the current path is provided, but stacking faults increase due to dislocations
Solution Approach 1:
The invention extracts the reflux current path function from the body diode structure and implements it through a separate second cell without a gate electrode. This separation removes the harmful effect of stacking faults and dislocations associated with body diode operation, while maintaining the necessary reflux current path functionality, thus resolving the contradiction between reliability and manufacturing precision.
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 effectively limits the reduction in current flowing from source to drain when the semiconductor device is in an OFF state, reducing the risk of degradation and maintaining device performance.
Implementation Method 1
an insulating film provided on the second silicon carbide semiconductor layer, the first cell includes a gate electrode on the second silicon carbide semiconductor layer with the insulating film provided between the second silicon carbide semiconductor layer and the gate electrode
Implementation Method 2
a first ohmic electrode which is in ohmic contact with the second region
Data Source
AI summary
A semiconductor device includes a first cell and a second cell. Each of the first cell and the second cell includes a first silicon carbide semiconductor layer including a first region and a second region provided in the first region, a second silicon carbide semiconductor layer provided on and in contact with the first silicon carbide semiconductor layer, a first ohmic electrode in ohmic contact with the second region, and an insulating film provided on the second silicon carbide semiconductor layer. The first cell includes a gate electrode, and the second cell includes no electrode configured to control the electric potential of the second silicon carbide semiconductor layer independently of the electric potential of the first ohmic electrode.