SiC Power MOSFET with Integrated Schottky Junction
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Solution Overview
Problem
SiC-based power MOSFET devices suffer from high forward voltage drop and bipolar degradation due to their integrated body diodes, leading to increased conduction losses and potential device degradation, especially at high switching frequencies.
Innovation Solution
The semiconductor device incorporates a SiC material with trenches featuring shielding regions and non-linear junctions, such as Schottky diodes, to reduce conduction losses and mitigate bipolar degradation by forming a conductive channel along the trenches and using shielding regions to manage electric fields and reduce stress on the gate dielectric.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a bipolar body diode is integrated in SiC power MOSFET, then the device structure is simple, but the forward voltage drop is high (2.7V to 4V) causing increased conduction losses
Solution Approach 1:
The body diode function is segmented into two separate structures: a bipolar body diode for high-voltage blocking and a unipolar Schottky diode for low-loss conduction. This segmentation allows each diode type to operate in its optimal performance regime, resolving the contradiction between structural simplicity and low conduction losses.
Solution Approach 2:
The patent merges a bipolar body diode and a unipolar Schottky diode into a single integrated device structure. The Schottky diode is formed by creating a Schottky junction between a metal electrode and the SiC body, while the bipolar body diode is formed by the pn junction between the body region and drift region. This merging allows the device to achieve both low conduction losses (via Schottky diode) and high-voltage blocking capability (via bipolar body diode).
2Device complexity
If a bipolar body diode is used, then the device structure is simple, but bipolar degradation effects occur due to recombination energy transferring to the crystal
Solution Approach 1:
The body diode function is segmented into two separate structures: a bipolar body diode for high-voltage blocking and a unipolar Schottky diode for low-loss conduction. This segmentation allows each diode type to operate in its optimal performance regime, resolving the contradiction between structural simplicity and low conduction losses.
Solution Approach 2:
The patent converts the harmful bipolar degradation mechanism into a beneficial configuration by using the Schottky diode for nominal current conduction. The unipolar Schottky conduction prevents recombination energy transfer to the crystal, thereby eliminating the harmful bipolar degradation effects while maintaining the necessary diode functionality.
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 minimizes conduction losses and bipolar degradation, enhancing the reliability and performance of SiC-based power semiconductor devices by reducing the forward voltage drop and protecting the gate dielectric from excessive electric fields.
Implementation Method 1
a non-linear junction formed with the SiC material at the bottom of a second subset of the trenches different than the first subset
Implementation Method 2
a body region of a second conductivity type adjacent the opposing sidewalls of each trench, wherein a conductive channel is configured to form in the body region along the opposing sidewalls of the trenches
Implementation Method 3
a shielding region of the second conductivity type at the bottom of a first subset of the trenches, each shielding region being electrically connected to the corresponding first electrode through an opening in an insulating material at the bottom of the first subset of trenches
Data Source
AI summary
Embodiments of SiC devices and corresponding methods of manufacture are provided. In some embodiments, the SiC device has shielding regions at the bottom of some gate trenches and non-linear junctions formed with the SiC material at the bottom of other gate trenches. In other embodiments, the SiC device has the shielding regions at the bottom of the gate trenches and arranged in rows which run in a direction transverse to a lengthwise extension of the trenches. In still other embodiments, the SiC device has the shielding regions and the non-linear junctions, and wherein the shielding regions are arranged in rows which run in a direction transverse to a lengthwise extension of the trenches.