SiC MOSFET Channel Mobility via Crystal Tilt and Nitrogen Concentration
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Solution Overview
Problem
Silicon carbide semiconductor devices face challenges in achieving high and reproducible channel mobility, as existing MOSFETs may not consistently exhibit sufficient channel mobility.
Innovation Solution
A silicon carbide semiconductor device with a semiconductor layer tilted at an angle between 50° and 65° relative to the {0001} plane, an insulating film contacting the semiconductor layer, and a nitrogen concentration of at least 1×10^21 cm^-3 within 10 nm of the interface, along with specific impurity diffusion layers and electrode configurations, is developed to enhance channel mobility and reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a MOSFET is formed using a conventional SiC substrate with surface orientation of substantially {03-38}, then a gate oxide film can be formed by dry oxidation, but the channel mobility is not sufficiently high and not reproducible
Solution Approach 1:
The patent changes the crystal plane orientation parameter from conventional {03-38} to a tilted plane within 50°-65° relative to {0001}, and optimizes nitrogen concentration to 1×10^21 cm^-3 or higher within 10 nm of the interface. These parameter changes enable both high channel mobility (exceeding 100 cm²/Vs) and reproducible results across different devices.
Solution Approach 2:
The patent applies local quality by creating a specific nitrogen concentration distribution localized within 10 nm from the semiconductor layer-insulating film interface, while maintaining a tilted crystal plane structure in the channel region. This localized optimization of nitrogen concentration at the interface region specifically enhances channel mobility without affecting other device regions.
2Reliability
If the semiconductor layer surface is tilted at an angle between 50° and 65° relative to the {0001} plane, then high channel mobility is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent specifies a quantitative range (50°-65°) for the crystal plane tilt angle, transforming an abstract structural modification into a precise manufacturable parameter. This defined range enables standardization of the tilted plane structure in production, reducing complexity despite the non-conventional orientation.
Solution Approach 2:
The patent performs preliminary action by pre-defining the optimal tilt angle range and nitrogen concentration distribution before device fabrication. This advance specification of structural parameters guides the manufacturing process, ensuring that the tilted plane structure is correctly formed from the outset, thereby simplifying subsequent processing steps.
3Reliability
If nitrogen concentration is increased to at least 1×10^21 cm^-3 within 10 nm from the interface, then channel mobility improves, but the risk of nitrogen precipitation increases
Solution Approach 1:
The patent confines high nitrogen concentration (≥1×10^21 cm^-3) to a localized region within 10 nm from the semiconductor layer-insulating film interface, rather than distributing it uniformly throughout the semiconductor layer. This localized placement provides sufficient nitrogen for high channel mobility at the critical interface region while avoiding excessive nitrogen accumulation in the bulk that would cause precipitation.
Solution Approach 2:
The patent optimizes the nitrogen concentration parameter by establishing a specific threshold (1×10^21 cm^-3) and spatial constraint (within 10 nm of interface). This precise parameter control ensures adequate nitrogen for enhancing channel mobility while maintaining conditions that prevent nitrogen precipitation, balancing performance and reliability.
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 solution achieves high channel mobility with high reproducibility by optimizing the crystal plane tilt, nitrogen concentration, and electrode patterns, reducing ON resistance and ensuring stable electrical characteristics.
Implementation Method 1
a semiconductor layer made of silicon carbide and having a surface tilted at an angle in a range of not less than 50° and not more than 65° relative to a {0001} plane
Implementation Method 2
a maximum value of a nitrogen concentration in a region within 10 nm from an interface between the semiconductor layer and the insulating film is not less than 1×10^21
Implementation Method 3
an insulating film formed to contact the surface of the semiconductor layer
Data Source
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AI summary
A silicon carbide semiconductor device (1, 100) is provided that includes a semiconductor layer (12) made of silicon carbide and having a surface tilted at an angle in a range of not less than 50° and not more than 65° relative to the {0001} plane, and an insulating film (13) formed to contact the surface (12a) of the semiconductor layer (12). A maximum value of the nitrogen concentration in a region within 10 nm from the interface between the semiconductor layer (12) and the insulating film (13) is not less than 1×1021 cm-3, and the semiconductor device has a channel direction in a range of ±10° relative to the direction orthogonal to the <-2110> direction in the surface (12a) of the semiconductor layer (12). A method of manufacturing the silicon carbide semiconductor device is also provided.