SiC Single-Crystal Substrate Off-Angles for Low Dislocation Growth
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Solution Overview
Problem
The challenge in manufacturing large-diameter SiC single crystal substrates is achieving the same dislocation density as smaller substrates, as larger substrates tend to have higher dislocation densities when using manufacturing techniques optimized for smaller sizes, leading to quality issues and reduced yield in mass production.
Innovation Solution
The development of a SiC single crystal substrate with specific off-angles and the inclusion of non-MP defects, which are hexagonal and coreless, with etch pit areas within defined ranges, helps in stress relaxation and reducing ion implantation damage, thereby maintaining a small change in SORI before and after ion implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If manufacturing conditions optimized for 6-inch substrates are applied to 8-inch substrates, then production efficiency increases, but dislocation density increases and crystal quality deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing crystal growth temperature gradients, pressure conditions, and composition ratios specific to 8-inch substrates. The temperature gradient in the radial direction is controlled at 20°C/cm or less, and in the vertical direction at 0°C/cm to 50°C/cm, which differs from conventional 6-inch substrate parameters, thereby achieving low dislocation density in large-diameter substrates.
Solution Approach 2:
The patent implements local quality by creating specific temperature distribution zones during crystal growth. The temperature gradient control creates different thermal environments in radial and vertical directions, allowing optimal growth conditions in each zone to minimize dislocation formation while maintaining high productivity for 8-inch substrates.
2Productivity
If the diameter is increased from 6 inch to 8 inch, then production efficiency and energy saving improve, but thermal decomposition occurs around the outer peripheral portion of the seed crystal
Solution Approach 1:
The patent changes the temperature gradient parameter to prevent thermal decomposition. By controlling the radial temperature gradient at 20°C/cm or less and the vertical temperature gradient at 0°C/cm to 50°C/cm, the patent ensures uniform temperature distribution that prevents thermal decomposition at the outer peripheral portion of the seed crystal during 8-inch substrate production.
Solution Approach 2:
The patent applies beforehand cushioning by pre-establishing optimal temperature gradient conditions before crystal growth begins. The controlled temperature distribution acts as a protective measure against thermal decomposition, ensuring that the seed crystal and growing crystal remain within safe thermal parameters throughout the growth process.
3Manufacturing precision
If manufacturing conditions for smaller substrates are used, then crystal quality is maintained, but production efficiency and cost reduction opportunities are lost
Solution Approach 1:
The patent changes the manufacturing parameters to accommodate larger substrate dimensions while maintaining crystal quality. The specific temperature gradient controls (radial: 20°C/cm or less, vertical: 0°C/cm to 50°C/cm) and pressure conditions are optimized for 8-inch substrates, enabling high-quality crystal growth at larger scales with improved production efficiency.
Solution Approach 2:
The patent achieves universality by developing a manufacturing method that can produce high-quality substrates across different sizes (6-inch and 8-inch). The optimized parameters create a flexible manufacturing system that maintains crystal quality standards while adapting to larger substrate dimensions for enhanced productivity.
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 yield and quality of large-diameter SiC single crystal substrates by effectively managing dislocation density and ion implantation-induced stress, enhancing the substrate's performance in device fabrication.
Implementation Method 1
the change in SORI before and after the ion implantation was small
Implementation Method 2
non-MP defects that provide stress relaxation
Data Source
AI summary
A SiC single crystal substrate of an embodiment is a SiC single crystal substrate wherein the main plane of the SiC single crystal substrate has an off angle of 0° to 6° to the (0001) plane in the <11-20> direction and an off angle of 0° to 0.5° to the (0001) plane in the <1-100> direction, and includes non-MP defects wherein when the Si surface is etched in molten KOH at 500° C. for 15 minutes, the non-MP defects that appear by etching are hexagonal and have no core, the area of the observed etch pit of the non-MP defect is more than 10% larger than that of the observed etch pit of the TSD and is less than 110% of that of the observed etch pit of the micropipe (MP), and a transmission X-ray topography image of the non-MP defect is distinguishable from the transmission X-ray topography image of the micropipe (MP), wherein etch pits, which are identified as the non-MP defects, appear in the range of 0.1/cm2 to 50/cm2.