SiC Gate Dielectric Structure Using Al-Doped Oxidation to Cut Interface States
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Solution Overview
Problem
The existing gate dielectric layers in SiC MOS devices suffer from high interface state density and reduced channel mobility due to the direct thermal oxidation method, limiting the performance and reliability of these devices.
Innovation Solution
A dielectric structure is formed by Al doping the surface of a SiC substrate followed by thermal oxidation, resulting in a dielectric layer that includes at least a SiAlO layer, which reduces the interface state density and improves the quality of the gate dielectric.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If direct thermal oxidation method is used to form gate dielectric layer on SiC substrate, then the dielectric layer can be formed, but the interface state density is high and channel mobility is reduced
Solution Approach 1:
The patent applies preliminary action by performing Al doping on the SiC substrate surface before thermal oxidation. This pre-treatment modifies the substrate surface properties, creating an Al-doped layer that serves as a foundation for subsequent oxidation. The Al doping concentration is controlled at 1E15-1E16 atoms/cm³, which prepares the surface to form a lower interface state density dielectric layer while improving channel mobility, thus resolving the contradiction between interface quality and device performance.
Solution Approach 2:
The patent employs parameter changes by modifying the chemical composition and doping concentration of the SiC substrate surface. Specifically, Al doping concentration is adjusted to 1E15-1E16 atoms/cm³, and thermal oxidation temperature is controlled at 900-1100°C. These parameter changes transform the substrate surface properties, enabling formation of a dielectric layer with reduced interface state density and improved channel mobility, thereby resolving the technical contradiction.
2Reliability
If Al doping is performed on SiC substrate followed by thermal oxidation, then the interface state density is reduced and channel mobility is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent merges the doping process with the dielectric layer formation process. Instead of separate doping and oxidation steps that would increase complexity, the Al doping is performed immediately before thermal oxidation, and the Al-doped layer serves dual purposes: as the doping region and as the precursor for dielectric layer formation. This merging of functions reduces process complexity while achieving improved channel mobility through reduced interface state density.
3Manufacturing precision
If Al doping concentration is increased to reduce interface state density, then the dielectric layer quality improves, but the doping process control difficulty increases
Solution Approach 1:
The patent specifies a precise Al doping concentration range of 1E15-1E16 atoms/cm³, which is optimized to achieve the desired dielectric layer quality without excessive interface state reduction that would complicate process control. This parameter optimization balances dielectric layer quality improvement with manageable doping process control, avoiding the need for extremely precise ultra-low or ultra-high doping concentrations that would increase measurement and control difficulty.
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 proposed solution significantly reduces the interface state density between SiC and the dielectric layer, enhancing channel mobility and forward conduction capability, thereby improving the overall performance and reliability of SiC MOS devices.
Implementation Method 1
performing Al doping to at least part of the first surface of the SiC substrate to form an Al-doped SiC layer
Implementation Method 2
oxidizing the Al-doped SiC layer through a thermal oxidation process to form a dielectric layer on the SiC substrate
Data Source
AI summary
Disclosed are a dielectric structure, a semiconductor device structure, and manufacturing methods therefor. The manufacturing method for the dielectric structure includes: performing Al doping to a surface of a SiC substrate to form an Al-doped SiC layer and then oxidizing the Al-doped SiC layer to form a dielectric layer including at least a SiAlO layer. On one hand, thermal oxidation temperature required for oxidizing SiC to SiO2 may be reduced, so that an interface state with a high density at an interface of SiC/SiO2 is reduced, and quality of the dielectric layer is improved. On the other hand, original Si in the SiO2 is replaced with Al, a more stable structure may be formed, and the quality of the dielectric layer is further improved.