SiC MOSFET Threshold Voltage Control via Nitrogen Gradient
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Solution Overview
Problem
Silicon carbide (SiC) MOSFETs typically have lower threshold voltage and mobility compared to silicon MOSFETs, necessitating a solution to enhance these parameters for improved performance in semiconductor devices.
Innovation Solution
Incorporating specific elements like sulfur, selenium, or nitrogen into the silicon carbide layer with precise concentration gradients to form deep levels and negative fixed charges, which increase threshold voltage and mobility, while also improving the reliability and oxidation resistance of the gate insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If silicon carbide is used as the semiconductor material, then breakdown field strength and thermal conductivity are improved, but threshold voltage and mobility deteriorate
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of nitrogen atoms within the silicon carbide layer. The nitrogen concentration is highest at the interface with the gate insulating layer and decreases toward the bulk, forming localized regions with different electrical properties. This gradient structure allows the interface region to have higher threshold voltage while the bulk maintains the inherent high breakdown field strength of silicon carbide.
Solution Approach 2:
The patent changes the chemical composition parameter of the silicon carbide layer by incorporating nitrogen atoms with a specific concentration gradient. This parameter change transforms the electrical characteristics of the material, increasing the threshold voltage at the interface region while preserving the overall superior physical properties of silicon carbide including its high breakdown field strength and thermal conductivity.
2Strength
If silicon carbide is used as the semiconductor material, then breakdown field strength and thermal conductivity are improved, but mobility deteriorates
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of nitrogen atoms within the silicon carbide layer. The nitrogen concentration is highest at the interface with the gate insulating layer and decreases toward the bulk, forming localized regions with different electrical properties. This gradient structure allows the interface region to have higher threshold voltage while the bulk maintains the inherent high breakdown field strength of silicon carbide.
Solution Approach 2:
The patent changes the chemical composition parameter of the silicon carbide layer by incorporating nitrogen atoms with a specific concentration gradient. This parameter change transforms the electrical characteristics of the material, increasing the threshold voltage at the interface region while preserving the overall superior physical properties of silicon carbide including its high breakdown field strength and thermal conductivity.
3Device complexity
If gate insulating layer is formed on silicon carbide, then device structure is completed, but interface scattering increases and reliability decreases
Solution Approach 1:
The patent applies preliminary action by pre-modifying the silicon carbide layer interface before forming the gate insulating layer. Nitrogen atoms are incorporated into the silicon carbide layer at the interface region in advance, creating a prepared interface structure that reduces scattering and improves reliability. This preliminary modification ensures that when the gate insulating layer is subsequently formed, the interface already has optimized electrical properties.
Solution Approach 2:
The patent changes the chemical composition parameter of the silicon carbide layer by incorporating nitrogen atoms with a specific concentration gradient. This parameter change transforms the electrical characteristics of the material, increasing the threshold voltage at the interface region while preserving the overall superior physical properties of silicon carbide including its high breakdown field strength and thermal conductivity.
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 approach results in SiC MOSFETs with higher threshold voltage and mobility, reduced interface scattering, and enhanced reliability of the gate insulating layer, addressing the limitations of conventional SiC MOSFETs.
Implementation Method 1
the silicon carbide layer includes at least one first element selected from the group consisting of sulfur (S), selenium (Se), tellurium (Te), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), and tungsten (W)... a first distance between a first position in the silicon carbide layer and an interface between the gate insulating layer and the silicon carbide layer is equal to or less than 20 nm, and the first position is a position where a concentration of the at least one first element is maximized
Data Source
AI summary
A semiconductor device according to an embodiment includes a gate electrode, a gate insulating layer, and a silicon carbide layer. The silicon carbide layer includes at least one first element selected from the group consisting of S, Se, Te, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. The first distance between a first position and an interface between the gate insulating layer and the silicon carbide layer is equal to or less than 20 nm, and the first position is a position where a concentration of the first element is maximized. The second distance between a second position and the interface is equal to or less than 20 nm, second position is a position where a concentration of the first element is 1/10 of a concentration of the first element at the first position, and the second position is farther from the interface than the first position.