SiC Gate Oxide Nitriding for Uniform Films and Low Interface Carbon
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Solution Overview
Problem
Conventional methods for manufacturing silicon carbide semiconductor devices face challenges in achieving uniform gate insulating film thickness and reducing residual carbon at the SiO2/SiC interface, leading to degradation of device characteristics and increased leak current due to excessive oxidation and nitrogen loss during the nitriding process.
Innovation Solution
A method involving a two-stage nitriding heat treatment process, where the first stage uses a gas mixture of oxygen and nitrogen to minimize oxidation and form a high-quality SiO2 film, followed by a second stage with a higher nitrogen content to ensure uniform nitridation and reduce post-oxidation, combined with high-temperature oxidation to deposit the oxide film, thereby suppressing excess carbon and enhancing interface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal oxidation is used to form the gate insulating film, then the film thickness is uniform and film quality is favorable, but excess carbon occurs at the SiO2/SiC interface causing degradation of device characteristics
Solution Approach 1:
The nitriding process is divided into two distinct stages: first stage nitriding before oxide film formation, and second stage nitriding after oxide film formation. This segmentation allows each stage to serve a specific function - the first stage prevents excess carbon formation at the interface, while the second stage ensures uniform nitridation throughout the film, thereby resolving the contradiction between film quality and interface carbon accumulation.
Solution Approach 2:
The first stage nitriding is performed as a preliminary action before oxide film formation. By nitriding the SiC substrate first, the interface is prepared in advance to prevent excess carbon occurrence during subsequent thermal oxidation, thus preventing the harmful effect before it can occur.
2Ease of manufacture
If deposited SiO2 film is used by plasma CVD or sputtering, then the manufacturing process is simplified, but film density and insulation performance are insufficient
Solution Approach 1:
The invention changes the chemical composition parameters of the gate insulating film by introducing nitrogen through two-stage nitriding processes. This transforms ordinary SiO2 into nitrided SiO2, significantly improving film density and insulation performance while maintaining the advantages of thermal oxidation processing.
3Manufacturing precision
If high-temperature oxidation is used to deposit oxide film, then uniform thickness is achieved, but nitrogen is lost during the nitriding process due to excessive oxidation
Solution Approach 1:
The nitriding process is divided into two distinct stages: first stage nitriding before oxide film formation, and second stage nitriding after oxide film formation. This segmentation allows each stage to serve a specific function - the first stage prevents excess carbon formation at the interface, while the second stage ensures uniform nitridation throughout the film, thereby resolving the contradiction between film quality and interface carbon accumulation.
Solution Approach 2:
The two-stage nitriding process ensures continuous and uniform nitrogen incorporation throughout the gate insulating film formation process. By performing nitriding both before and after oxide film deposition, the useful action of nitrogen incorporation is maintained continuously, preventing nitrogen loss and ensuring uniform distribution throughout the final film structure.
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 results in improved device characteristics, including increased mobility and reduced threshold voltage variability, while minimizing leak current in low electric field regions, thus enhancing the reliability of silicon carbide semiconductor devices.
Implementation Method 1
under an oxygen atmosphere, an oxide film is deposited by a chemical reaction (chemical vapor deposition method) such as high-temperature oxidation for a high temperature oxide (HTO) or thermal oxidation at a temperature of about 1000 degrees C.
Implementation Method 2
performing a nitriding heat treatment by nitric oxide (NO) or a mixed gas of nitrogen (N2) and nitric oxide (NO)
Data Source
AI summary
A process of forming a gate insulating film in a silicon carbide semiconductor device. The process includes performing a first stage of a nitriding heat treatment by a gas containing oxygen and nitrogen, followed by depositing an oxide film, and then performing a second stage of the nitriding heat treatment by a gas containing nitric oxide and nitrogen. The amount of nitrogen at the treatment starting point of the first stage of the nitriding heat treatment is greater than the amount of nitrogen at the treatment starting point of the second stage of the nitriding heat treatment. The amount of nitrogen at the treatment ending point of the second stage of the nitriding heat treatment is greater than the amount of nitrogen at the treatment ending point of the first stage of the nitriding heat treatment.