Silicon Oxide Layer Formation via Oxygen Radical Oxidation
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Solution Overview
Problem
Current methods for forming silicon oxide layers, particularly for gate oxides in vertical power devices and silicon carbide wafers, face challenges such as impurity absorption, low density, non-conformity, and quality issues due to the use of toxic nitrogen oxides, and struggle to achieve high-quality gate oxides with acceptable effort and expense.
Innovation Solution
A method involving the formation of a silicon nitride layer followed by oxygen radical oxidation to produce a high-quality silicon oxide layer with controlled nitrogen content, reducing impurity absorption and achieving conformal coverage without the need for toxic nitrogen oxides, thereby enhancing the quality and reliability of gate oxides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal oxidation is used to form silicon oxide layers, then high quality oxide is obtained with good density and conformity, but impurities are absorbed from the silicon-containing substrate
Solution Approach 1:
A silicon nitride intermediate layer is deposited on the silicon-containing substrate before oxidation. This intermediate layer acts as a barrier that prevents impurity absorption from the substrate while allowing the formation of high-quality silicon oxide. The silicon nitride layer is then oxidized in-situ to form the final silicon oxide layer, eliminating the need for separate cleaning steps.
2Ease of manufacture
If CVD oxide deposition is used on silicon carbide wafers, then gate oxides can be formed, but the oxide quality and interface quality are severely restricted with high defect density
Solution Approach 1:
A silicon nitride layer is deposited on the silicon carbide wafer surface before the oxidation process. This preliminary layer provides a high-quality foundation that enables subsequent formation of low-defect silicon oxide gate structures. The silicon nitride layer protects the silicon carbide surface and provides a controlled interface for oxide growth.
Solution Approach 2:
The process uses oxygen radical oxidation instead of conventional CVD deposition, fundamentally changing the oxidation mechanism. This parameter change enables the formation of high-quality silicon oxide with low defect density and excellent interface quality on silicon carbide substrates, overcoming the limitations of standard CVD methods.
3Reliability
If conventional heat treatment with nitrogen monoxide or nitrogen dioxide is used, then interface states can be reduced, but toxic and fire-promoting materials require particular effort and expense
Solution Approach 1:
The process uses oxygen radicals as a strong oxidant to convert the silicon nitride layer to silicon oxide in-situ. This accelerated oxidation method achieves excellent interface quality and reduces interface states without requiring toxic nitrogen oxides. The oxygen radical oxidation is more effective and cleaner than conventional heat treatment methods.
Solution Approach 2:
The invention extracts and eliminates the need for toxic nitrogen oxide gases from the process. By using oxygen radical oxidation instead of nitrogen-based heat treatment, the process removes the harmful materials and associated safety requirements while maintaining or improving interface quality.
4Ease of manufacture
If deposited oxide is used instead of thermal oxidation, then lower density and less conformity are achieved, but the process may be simpler
Solution Approach 1:
The silicon nitride intermediate layer enables a deposition-like process to achieve thermal oxidation-quality results. The silicon nitride is deposited conformally and then oxidized in-situ, combining the simplicity of deposition with the high quality of thermal oxidation. This intermediate layer approach allows deposited oxide to achieve both good density and conformity.
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 silicon oxide layers with improved density, conformity, and reliability, reducing leakage and interface states, and allows for the production of high-quality gate oxides on silicon carbide wafers with reduced thermal budget and operational costs.
Implementation Method 1
A silicon oxide layer is formed from at least a vertical section of the silicon nitride layer by oxygen radical oxidation
Data Source
AI summary
A body structure and a drift zone are formed in a semiconductor layer, wherein the body structure and the drift zone form a first pn junction. A silicon nitride layer is formed on the semiconductor layer. A silicon oxide layer is formed from at least a vertical section of the silicon nitride layer by oxygen radical oxidation.