SiC MOSFET Gate Insulator Corner Oxide Growth
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Solution Overview
Problem
The reliability of silicon carbide (SiC) MOSFET devices is compromised due to high electric fields at sharp corners of the gate electrode, which can lead to device failure, especially when operating at high electric fields greater than 4 MV/cm.
Innovation Solution
A method involving the oxidation process after forming the gate electrode, where an oxide layer is grown between the gate insulating layer and the gate electrode, increasing the thickness of the insulating layer at corners to reduce electric field concentrations, is performed in an environment with a hydrogen-to-oxygen ratio of at least 0.03:1 at temperatures less than 950 degrees Celsius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a thin gate insulating layer is used to achieve low threshold voltage and high drive current, then device performance is improved, but electric field concentration at gate electrode corners increases leading to reliability degradation
Solution Approach 1:
The patent applies local quality by creating a non-uniform gate insulating layer structure where the thickness varies spatially. Specifically, the gate insulating layer is made thicker at the corner regions adjacent to the gate electrode edges compared to the center region. This local thickening at corners reduces electric field concentration in these critical areas while maintaining the overall thin layer structure needed for device performance.
Solution Approach 2:
The patent implements beforehand cushioning by pre-positioning thicker insulating material at the corner regions before the device operates under high electric field conditions. This proactive structural design cushions the corner regions against electric field concentration and potential breakdown, preventing reliability issues before they occur during device operation.
2Reliability
If the gate insulating layer thickness is increased at corners to reduce electric field concentration, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs self-service by utilizing the natural tendency of oxidation processes to occur at high-field regions. The corner regions, which experience highest electric field stress during operation, automatically receive more oxide growth during thermal oxidation processes. This self-service mechanism creates the required thickness variation without requiring complex external patterning or precise manual control.
Solution Approach 2:
The patent applies parameter changes by utilizing thermal oxidation parameters (temperature, time, atmosphere) to dynamically control oxide growth. By adjusting oxidation conditions, the process naturally produces thicker insulation at corners where electric field concentration is highest, transforming a manufacturing precision challenge into a controllable physical process outcome.
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 approach enhances the reliability of SiC MOSFET devices by reducing electric field peaks at corners, maintaining key electrical properties such as threshold voltage, leakage current, and on-state source-drain resistance, and significantly improving the device's operational lifespan.
Implementation Method 1
an oxidation process after forming the gate electrode, where an oxide layer is grown between the gate insulating layer and the gate electrode
Data Source
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AI summary
A semiconductor device is presented. The device includes a semiconductor layer including silicon carbide, and having a first surface and a second surface. A gate insulating layer is disposed on a portion of the first surface of the semiconductor layer, and a gate electrode is disposed on the gate insulating layer. The device further includes an oxide disposed between the gate insulating layer and the gate electrode at a corner adjacent an edge of the gate electrode so as the gate insulating layer has a greater thickness at the corner than a thickness at a center of the layer. A method for fabricating the device is also provided.