SiC Epitaxial Substrate Haze and Carrier Uniformity Control
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Solution Overview
Problem
The existing silicon carbide epitaxial substrates face challenges in achieving both high surface flatness and in-plane uniformity of carrier concentration, particularly on the Si plane side, where improving surface flatness while maintaining uniformity is difficult due to variations in the C/Si ratio and residual nitrogen distribution.
Innovation Solution
The silicon carbide epitaxial substrate is manufactured with a silicon carbide single crystal substrate and a silicon carbide layer, where the surface haze is controlled to be less than or equal to 75 ppm, and the C/Si ratio is uniformly distributed across the substrate to enhance in-plane uniformity and surface flatness, using a hot wall-type CVD method with specific gas flow and temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the C/Si ratio is increased to improve surface flatness, then surface flatness is improved, but in-plane uniformity of carrier concentration deteriorates due to variations in nitrogen distribution
Solution Approach 1:
The patent applies parameter changes by precisely controlling the C/Si ratio within a specific range (0.95-1.05) and managing nitrogen partial pressure during epitaxial growth. This resolves the contradiction by finding an optimal parameter window that simultaneously achieves surface flatness (through adequate C/Si ratio) and carrier concentration uniformity (through controlled nitrogen distribution), rather than relying on extreme values that would compromise one parameter.
Solution Approach 2:
The patent implements local quality control by maintaining different conditions in different regions of the growth chamber and across the substrate surface. By creating a controlled nitrogen environment that ensures uniform distribution across the substrate, the patent achieves both surface flatness and carrier concentration uniformity without the trade-off that would occur with uniform high C/Si ratio throughout.
2Stability of the object's composition
If the C/Si ratio is decreased to improve carrier concentration uniformity, then in-plane uniformity is improved, but surface flatness deteriorates
Solution Approach 1:
The patent resolves this contradiction by establishing a minimum C/Si ratio threshold (0.95-1.05) that ensures sufficient surface flatness while preventing excessive nitrogen incorporation that would harm carrier concentration uniformity. This parameter optimization allows both requirements to be satisfied simultaneously.
Solution Approach 2:
The patent employs feedback control mechanisms to monitor and adjust the C/Si ratio and nitrogen partial pressure during epitaxial growth. By implementing real-time control, the system can maintain surface flatness and carrier concentration uniformity together, preventing the deterioration that would occur with static low C/Si ratio conditions.
3Quantity of substance
If nitrogen partial pressure is increased to enhance carrier concentration, then carrier concentration is improved, but surface flatness deteriorates due to step bunching
Solution Approach 1:
The patent resolves this contradiction by optimizing nitrogen partial pressure within a controlled range that provides sufficient carrier concentration while preventing step bunching. By carefully balancing nitrogen supply with other growth parameters (temperature, pressure, gas flow), the patent achieves both high carrier concentration and surface flatness without the trade-off.
Solution Approach 2:
The patent applies dynamic control of nitrogen partial pressure during the epitaxial growth process, adjusting it in response to real-time conditions. This dynamic approach allows the system to maintain high carrier concentration while preventing step bunching, as the nitrogen pressure is modulated to match the evolving growth state rather than being held at a fixed high value.
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 reliability of the insulating film, as indicated by increased charge-to-breakdown values, and achieves better surface flatness and carrier concentration uniformity, enhancing the overall performance of silicon carbide semiconductor devices.
Implementation Method 1
silicon carbide layer which is on first main surface 11
Implementation Method 2
using a hot wall-type CVD method
Data Source
AI summary
A silicon carbide epitaxial substrate includes a silicon carbide single crystal substrate and a silicon carbide layer. The silicon carbide single crystal substrate has a first main surface. The silicon carbide layer is on the first main surface. The silicon carbide layer includes a second main surface opposite to a surface thereof in contact with the silicon carbide single crystal substrate. The second main surface has a maximum diameter of more than or equal to 100 mm. The second main surface includes an outer peripheral region which is within 3 mm from an outer edge of the second main surface, and a central region surrounded by the outer peripheral region. The central region has a haze of less than or equal to 75 ppm.