SiC MOSFET Gate Oxide Processing for Low Interface Defects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The defect density at the interface between the SiO2 film and the SiC substrate remains high, limiting the characteristics of SiC MOSFETs, and existing methods like NO thermal treatment are difficult to optimize due to competing oxidation and nitridation processes and the toxicity of NO gas, making them unsuitable for mass production.
Innovation Solution
A SiC semiconductor device manufacturing method involving high-temperature H2 gas etching of the SiC substrate surface followed by forming a SiO2 film under non-oxidizing conditions and subsequent thermal treatment in a N2 gas atmosphere at elevated temperatures to reduce interface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal oxidation is performed to form a SiO2 film on the SiC substrate surface, then a gate oxide film is formed, but the interface defect density becomes extremely high
Solution Approach 1:
The patent applies preliminary action by performing H2 gas etching on the SiC substrate surface before forming the SiO2 film. This pre-treatment step removes surface contaminants and prepares the substrate to reduce subsequent interface defect density, directly addressing the contradiction between forming a functional gate oxide and maintaining low interface defects.
Solution Approach 2:
The patent changes the chemical environment parameters by using H2 gas atmosphere for etching and N2 gas atmosphere for thermal treatment, instead of conventional oxygen-rich environments. This parameter change allows selective removal of carbon contaminants while preventing unwanted oxidation, thereby reducing interface defect density while maintaining SiC substrate integrity.
2Manufacturing precision
If NO gas thermal treatment is used for interface nitridation, then interface defect density is reduced, but oxidation also occurs and the process becomes difficult to optimize
Solution Approach 1:
The patent segments the nitridation process from oxidation by using separate H2 gas etching and N2 gas thermal treatment steps. This segmentation allows independent optimization of each step - the H2 etching removes carbon contaminants and the N2 treatment provides nitrogen incorporation - eliminating the competing reactions that occur with NO gas and simplifying process optimization.
Solution Approach 2:
The patent introduces H2 gas and N2 gas as intermediary substances to mediate the surface treatment process. Instead of using NO gas that simultaneously causes nitridation and oxidation, the two-step process with H2 and N2 as intermediaries achieves nitrogen incorporation while preventing oxidation, thereby resolving the optimization difficulty.
3Manufacturing precision
If NO gas is used for thermal treatment, then interface nitridation is achieved, but the process becomes unsuitable for mass production due to high toxicity
Solution Approach 1:
The patent replaces the toxic NO gas with H2 gas and N2 gas, which are safer and more suitable for mass production environments. Although H2 requires careful handling, it is widely available and can be easily managed with standard safety protocols, making the process economically viable for large-scale manufacturing while achieving the same interface defect reduction.
Solution Approach 2:
The patent converts the potential harm of using reactive gases into benefit by carefully selecting H2 and N2 gases that provide the desired interface treatment while being safer for mass production. The H2 gas etching step, which could potentially cause hydrogen embrittlement, is controlled to provide beneficial carbon removal, and the N2 gas step provides safe nitrogen incorporation without the toxicity of NO gas.
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
Significantly reduces interface defect density, improves SiC MOSFET characteristics by preventing substrate oxidation and ensuring a high-quality SiO2 film with stable properties, making the process more suitable for mass production.
Implementation Method 1
a step of etching a surface of a SiC substrate with H2 gas at a temperature of 1200°C or more
Implementation Method 2
a step of forming a SiO2 film on the SiC substrate under conditions where the SiC substrate is not oxidized
Implementation Method 3
a step of thermally treating the SiC substrate formed with the SiO2 film in N2 gas atmosphere at a temperature of 1350°C or more
Data Source
Figure 1(A)~1(D)
Figure 2
Figure 3~4
AI summary
A SiC semiconductor device manufacturing method includes a step of etching a surface of a SiC substrate 1 with H2 gas at a temperature of 1200°C or more, a step of forming a SiO2 film 3, 4 on the SiC substrate under conditions where the SiC substrate is not oxidized, and a step of thermally treating the SiC substrate formed with the SiO2 film in N2 gas atmosphere at a temperature of 1350°C or more.