SiC MOSFET Gate Oxide Nitrogen Concentration
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Solution Overview
Problem
Silicon carbide semiconductor devices, particularly MOSFETs, face challenges in achieving high and reproducible channel mobility due to the formation of interface states at the gate oxide film and SiC semiconductor film interface, leading to decreased mobility and high threshold voltage.
Innovation Solution
Increasing the concentration of nitrogen or hydrogen atoms in the vicinity of the interface between the semiconductor layer and the insulating film to suppress the influence of interface states, with a maximum concentration of at least 1×10^21 cm^-3 within 10 nm, and optimizing the substrate off-angle between 50° and 65° for improved carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dry oxidation is used to form the gate oxide film, then the MOSFET can be formed on SiC substrate, but the channel mobility decreases due to interface state formation
Solution Approach 1:
The patent changes the chemical composition parameters of the gate oxide film by incorporating nitrogen atoms (5-20 at%) or hydrogen atoms (5-20 at%) into the SiO2 matrix. This parameter change modifies the interface properties between the gate oxide and SiC semiconductor layer, reducing interface states and improving channel mobility while maintaining the dry oxidation formation process.
Solution Approach 2:
The patent creates a composite gate oxide film material with the chemical formula SiO2-xNyHz, combining silicon oxide with nitrogen and/or hydrogen elements. This composite material structure provides both the insulating properties of SiO2 and the interface quality improvement from nitrogen/hydrogen incorporation, resolving the contradiction between reliable MOSFET formation and high channel mobility.
2Manufacturing precision
If the concentration of nitrogen or hydrogen atoms is increased in the gate oxide film, then channel mobility improves, but the device complexity increases
Solution Approach 1:
The patent establishes specific parameter ranges for nitrogen (5-20 at%) and hydrogen (5-20 at%) concentrations in the gate oxide film. By defining these quantitative parameters, the patent simplifies the control of complex composition variations while ensuring optimal channel mobility. The parameters provide clear manufacturing targets that balance performance improvement with process controllability.
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 channel mobility and reduces on-state resistance, achieving sufficiently high carrier mobility and stable electrical characteristics in silicon carbide semiconductor devices.
Implementation Method 1
a maximum value of a concentration of nitrogen atoms in a region within 10 nm of an interface between the semiconductor layer and the insulating film is greater than or equal to 1×10^21 cm^-3
Implementation Method 2
the gate oxide film is formed by the dry oxidation
Data Source
AI summary
There is provided a silicon carbide semiconductor device having excellent electrical characteristics such as channel mobility, and a method for manufacturing the same. A semiconductor device includes a substrate made of silicon carbide and having an off-angle of greater than or equal to 50° and less than or equal to 65° with respect to a surface orientation of {0001}, a p-type layer serving as a semiconductor layer, and an oxide film serving as an insulating film. The p-type layer is formed on the substrate and is made of silicon carbide. The oxide film is formed to contact with a surface of the p-type layer. A maximum value of the concentration of nitrogen atoms in a region within 10 nm of an interface between the semiconductor layer and the insulating film (interface between a channel region and the oxide film) is greater than or equal to 1×1021 cm−3.