SiC Substrate Dislocation Control via Local Quality
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Solution Overview
Problem
Existing silicon carbide semiconductor substrates face challenges in improving the yield of semiconductor devices due to high dislocation densities, particularly in reducing screw dislocation density, which affects the manufacturing efficiency and quality of devices.
Innovation Solution
The approach focuses on reducing local dislocation density in specific areas of the substrate, ensuring that the density of dislocations with Burgers vectors parallel to certain directions is limited to no more than 1×10^5 cm^-2, and utilizing a 4H polytype silicon carbide substrate with a diameter of at least 4 inches to enhance manufacturing efficiency and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the average dislocation density of silicon carbide substrate is reduced, then the quality of semiconductor devices is improved, but the yield improvement is insufficient
Solution Approach 1:
The patent applies local quality by establishing different dislocation density requirements for different regions of the substrate. Specifically, the central area (excluding outer circumferential area within 5mm from outer circumference) requires dislocation density of at most 1×10^5 cm^-2 in any 1mm×1mm square area, while allowing higher densities in the outer circumferential area. This regional differentiation resolves the contradiction by focusing quality control where devices are manufactured while maintaining overall substrate usability for yield improvement.
2Reliability
If the dislocation density is reduced to 2500 cm^-2 or lower, then the crystal defect density is reduced, but the yield of semiconductor devices still cannot be improved
Solution Approach 1:
The patent implements local quality control by specifying that dislocation density requirements apply specifically to the central area of the substrate, excluding the outer circumferential area within 5mm from the outer circumference. This allows the central manufacturing area to meet strict quality standards while the outer areas can have higher defect densities, thereby improving overall substrate utilization and device yield without compromising crystal quality in device regions.
Solution Approach 2:
The patent segments the substrate into distinct functional zones: a central area for device manufacturing with strict dislocation density control (at most 1×10^5 cm^-2 in any 1mm×1mm square area), and an outer circumferential area within 5mm from the outer circumference that is excluded from these requirements. This segmentation resolves the contradiction by separating quality-critical regions from areas where defects are tolerable, thereby improving both reliability and productivity.
3Productivity
If the substrate diameter is increased to at least 4 inches, then the manufacturing efficiency is enhanced, but the control of local dislocation density becomes more challenging
Solution Approach 1:
The patent applies local quality control to large-diameter substrates (at least 4 inches) by establishing that dislocation density requirements apply specifically to the central area, excluding the outer circumferential area within 5mm from the outer circumference. This approach enables efficient use of large substrates for manufacturing while maintaining precise dislocation density control (at most 1×10^5 cm^-2 in any 1mm×1mm square area) in the central device fabrication regions, thereby resolving the contradiction between manufacturing efficiency and precision control.
Data Source
AI summary
A semiconductor substrate has a main surface and formed of single crystal silicon carbide. The main surface includes a central area, which is an area other than the area within 5 mm from the outer circumference. When the central area is divided into square areas of 1 mm×1 mm, in any square area, density of dislocations of which Burgers vector is parallel to <0001> direction is at most 1×105 cm−2. Thus, a silicon carbide semiconductor substrate enabling improved yield of semiconductor devices can be provided.