SiC Gate Oxide Film Two-Step Thermal Oxidation Process
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for forming gate oxide films in silicon carbide (SiC) MOS transistors result in high interface state densities and low channel mobility, failing to achieve excellent transistor characteristics.
Innovation Solution
A method involving a first thermal oxidation treatment followed by a second thermal oxidation treatment at a reduced oxygen concentration and oxidation speed of at most 5 nm/hour to increase the gate oxide film thickness, effectively terminating dangling bonds and reducing interface state densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a gate oxide film is formed by normal thermal oxidation method, then the film thickness can be increased, but the interface state density becomes high and channel mobility becomes low
Solution Approach 1:
The oxidation process is divided into multiple stages with different oxygen concentrations. The first stage uses high oxygen concentration (5-20%) to form the initial gate oxide film, and the second stage uses low oxygen concentration (0.1-5%) to grow the film thickness while controlling interface state density. This segmentation allows each stage to optimize for its specific function.
Solution Approach 2:
The oxygen concentration parameter is changed between stages. By reducing oxygen concentration from 5-20% in the first stage to 0.1-5% in the second stage, the oxidation rate is controlled to be at most 5 nm/hour, which effectively terminates dangling bonds and reduces interface state density while continuing to increase film thickness.
2Manufacturing precision
If wet oxidation is used to form gate oxide film, then channel mobility improves to about 50 cm2/Vs, but flat band shift remains high and characteristics are insufficient
Solution Approach 1:
The patent changes the oxygen concentration parameter to achieve optimal oxidation rate. By using low oxygen concentration (0.1-5%) in the second stage, the oxidation rate is controlled to at most 5 nm/hour, which creates a high quality oxide-silicon carbide interface that reduces flat band shift while maintaining good channel mobility.
Solution Approach 2:
The patent performs continuous oxidation in two stages without breaking the oxidation atmosphere. The second stage continues the oxidation process from the first stage, maintaining the oxidizing atmosphere throughout to ensure continuous film growth with controlled quality, achieving both good mobility and low flat band shift.
3Length of stationary object
If oxidation speed is increased to form thicker gate oxide film, then film thickness increases, but interface state density increases and transistor characteristics deteriorate
Solution Approach 1:
The oxygen concentration is changed to control the oxidation rate. By using low oxygen concentration (0.1-5%) in the second stage, the oxidation rate is limited to at most 5 nm/hour. This controlled slow growth allows the oxide film to thicken while maintaining a high quality interface with low state density, preserving transistor characteristics.
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 significantly reduces interface state densities and enhances channel mobility, enabling the production of MOS transistors with improved characteristics, such as high channel mobility and low flat band shift.
Implementation Method 1
forming a gate oxide film on an SiC region by a first thermal oxidation treatment in a first oxidizing atmosphere
Implementation Method 2
performing a second thermal oxidation treatment at an oxidation speed of at most 5 nm/hour in a second oxidizing atmosphere having a lower oxygen concentration than the first oxidizing atmosphere
Data Source
AI summary
A method for manufacturing a semiconductor device, includes forming a gate oxide film on an SiC region by a first thermal oxidation treatment in a first oxidizing atmosphere, performing a second thermal oxidation treatment at an oxidation speed of at most 5 nm/hour in a second oxidizing atmosphere having a lower oxygen concentration than the first oxidizing atmosphere, to increase film thickness of the gate oxide film, after the first thermal oxidation treatment, and forming a gate electrode on the gate oxide film with the increased film thickness.