Nitride Semiconductor Wafer Off-Axis Angle Control
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Solution Overview
Problem
Nitride semiconductor substrates exhibit inadequate and varying optical, electrical, and mechanical properties due to uncontrolled local variations in the off-axis angle, making it difficult to determine the optimum misorientation angle for epitaxial growth.
Innovation Solution
Controlling the local variation in the off-axis angle of the nitride semiconductor substrate within a specific range (greater than 0.05° to less than 1°) ensures uniform properties and improved substrate quality, allowing for the growth of high-quality epitaxial layers with reduced dislocation density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the off-axis angle is set to a specific value for epitaxial growth, then the crystalline properties of the nitride semiconductor layer are improved, but local variations in optical, electrical, and mechanical properties occur across the substrate surface
Solution Approach 1:
The patent applies local quality by intentionally creating a controlled gradient in the off-axis angle across the substrate surface. Different regions of the substrate have slightly different off-axis angles within a predetermined range, which compensates for local variations and achieves uniform device characteristics across the entire wafer surface.
Solution Approach 2:
The patent changes the off-axis angle parameter from a fixed value to a controlled range. By specifying that the off-axis angle varies within a predetermined range (greater than 0.05° to less than 1°), the patent transforms a single-parameter approach into a multi-parameter approach that accounts for local variations and achieves more consistent device performance.
2Ease of manufacture
If the off-axis angle is not controlled, then substrate manufacturing is simpler, but the optimum misorientation angle for epitaxial growth cannot be determined and device properties vary
Solution Approach 1:
The patent applies preliminary action by pre-controlling the off-axis angle distribution before the epitaxial growth process. The substrate is manufactured with a predetermined off-axis angle range, which prepares the surface in advance to ensure optimal and uniform epitaxial growth, eliminating the need for complex post-processing or trial-and-error optimization.
3Productivity
If the off-axis angle variation is not controlled, then substrate production is easier, but dislocation density increases and device reliability decreases
Solution Approach 1:
The patent changes the off-axis angle parameter from uncontrolled to controlled within a predetermined range. This parameter control reduces dislocation density by ensuring optimal misorientation for dislocation glide, thereby improving device reliability and performance consistency without significantly impacting substrate production efficiency.
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 manufacture of nitride semiconductor devices with enhanced optical, electrical, and mechanical properties, such as improved light-emitting elements, electronic devices, and SAW devices, by ensuring consistent substrate characteristics across the principal surface.
Implementation Method 1
epitaxially growing a flat and thin nitride semiconductor layer on a nitride semiconductor substrate
Data Source
AI summary
A nitride semiconductor substrate having properties preferable for the manufacture of various nitride semiconductor devices is made available, by specifying or controlling the local variation in the off-axis angle of the principal surface of the nitride semiconductor substrate. In a nitride semiconductor single-crystal wafer having a flat principal surface, the crystallographic plane orientation of the principal surface of the nitride semiconductor single-crystal wafer varies locally within a predetermined angular range.