Silicon Carbide Epitaxy on Silicon Substrates via Viscous Mask
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge lies in forming high-quality single crystal silicon carbide films with few crystal defects on silicon substrates due to significant differences in lattice constants and thermal expansion coefficients between silicon and silicon carbide, which leads to stress and defects during epitaxial growth, especially when trying to increase substrate diameter beyond current limitations.
Innovation Solution
A semiconductor substrate and method involving a mask material with a viscosity of 105 Pa·S to 1014.5 Pa·S in the temperature range of 950 to 1400°C, formed from a silicon oxide film doped with phosphorus, which absorbs stress caused by thermal expansion coefficient differences, allowing for the growth of high-quality single crystal silicon carbide films by propagating planar defects into the mask material and reducing viscosity to mitigate thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If single crystal silicon carbide is epitaxially grown on a silicon substrate, then the substrate diameter can be increased, but stress occurs due to difference in thermal expansion coefficient between substrate and single crystal silicon carbide
Solution Approach 1:
A mask material layer is introduced as an intermediary between the silicon substrate and the single crystal silicon carbide film. This mask material serves as a stress-absorbing buffer that accommodates the thermal expansion mismatch during cooling, preventing stress transmission to the silicon carbide film while allowing the substrate diameter to be increased.
Solution Approach 2:
The viscosity of the mask material is specifically controlled to be in the range of 10^5 to 10^14.5 Pa·s at temperatures of 950 to 1400°C. This parameter optimization ensures the mask material has appropriate mechanical properties at processing temperatures to absorb thermal stress effectively while maintaining structural integrity during epitaxial growth.
2Area of stationary object
If single crystal silicon carbide is epitaxially grown on a silicon substrate, then the substrate diameter can be increased, but crystal defects occur due to lattice constant difference
Solution Approach 1:
The mask material acts as a buffer layer that absorbs planar defects generated at the silicon substrate interface. By positioning the mask material between the substrate and the silicon carbide film, defects are prevented from propagating into the active device region, thereby maintaining high crystal quality even with larger substrate diameters.
Solution Approach 2:
Planar defects are extracted and contained within the mask material layer rather than allowing them to propagate into the single crystal silicon carbide film. The mask material serves as a defect sink, isolating the high-quality crystal growth region from the defective substrate interface.
3Strength
If the mask material has high viscosity, then it maintains structural integrity, but it cannot absorb stress caused by thermal expansion coefficient difference
Solution Approach 1:
The viscosity of the mask material is optimized to a specific range (10^5 to 10^14.5 Pa·s at 950-1400°C) that balances structural integrity and stress absorption capability. This parameter window ensures the material is neither too rigid nor too soft, allowing it to maintain shape while accommodating thermal expansion differences.
Solution Approach 2:
The mask material exhibits dynamic mechanical properties that adapt to processing conditions. At high temperatures during epitaxial growth, the material maintains sufficient rigidity for structural support, while at lower temperatures during cooling, it becomes more compliant to absorb thermal stress effectively.
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 enables the formation of high-quality single crystal silicon carbide films with reduced crystal defects by absorbing thermal stress, allowing for reliable epitaxial growth within the specified temperature range, thus overcoming the limitations of current substrate size and defect issues.
Implementation Method 1
the viscosity of the mask material is decreased in a temperature range of 950 to 1400° C. (for example, a temperature range in which a single crystal silicon carbide film is formed), and therefore, stress caused by a difference in thermal expansion coefficient of the single crystal silicon carbide film can be absorbed by the mask material
Implementation Method 2
single crystal silicon carbide is epitaxially grown
Data Source
AI summary
A semiconductor substrate includes: single crystal silicon; a mask material formed on a surface of the single crystal silicon and having an opening; a silicon carbide film formed on a portion exposed in the opening of the single crystal silicon; and a single crystal silicon carbide film formed so as to cover the silicon carbide film and the mask material. The mask material has a viscosity of 105 Pa·S or more and 1014.5 Pa·S or less in a temperature range of 950 to 1400° C.