Nitride Semiconductor Substrate C-Axis Control
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Solution Overview
Problem
In nitride semiconductor devices, such as HEMTs, the nitride semiconductor spacer layer is not flattened sufficiently, leading to degraded surface flatness and increased sheet resistance, which disrupts the increase of output power.
Innovation Solution
A compound semiconductor substrate and device with a nitride semiconductor layer having a c-axis length of 0.4990 nm or more, formed using TMAl or TEAl and NH3 as precursors by a MOVPE method at a growth rate of 12 nm/min or more, or a V/III ratio of 1000 or more, to achieve a flattened surface and reduce sheet resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional MOVPE growth conditions are used for the nitride semiconductor layer, then the growth process is simple and fast, but the surface flatness is degraded and sheet resistance increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the c-axis length of the nitride semiconductor layer (setting it to 0.4990 nm or more) and optimizing MOVPE growth conditions (growth rate of 12 nm/min or more, V/III ratio of 1000 or more). These parameter adjustments resolve the contradiction by achieving both improved surface flatness and reduced sheet resistance simultaneously, rather than treating them as separate optimization targets.
2Productivity
If the nitride semiconductor layer is grown at higher growth rates, then productivity increases, but surface morphology may be degraded
Solution Approach 1:
The patent resolves this contradiction by establishing specific parameter thresholds: growth rate of 12 nm/min or more and V/III ratio of 1000 or more. By changing and controlling these growth parameters within defined ranges, the patent achieves both high productivity through fast growth rates and good surface morphology, eliminating the traditional trade-off between speed and quality.
3Ease of manufacture
If the c-axis length of the nitride semiconductor layer is not controlled, then the fabrication process is simpler, but output power and reliability are reduced
Solution Approach 1:
The patent introduces a specific parameter control (c-axis length ≥ 0.4990 nm) that resolves the contradiction between manufacturing simplicity and device performance. While this adds a parameter to control, the patent provides clear guidance on achieving this through MOVPE conditions, making the process manageable while significantly improving output power and reliability compared to uncontrolled growth.
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 a low sheet resistance of 200 ohm/sq or less and improved surface morphology, enhancing the output power and reliability of the nitride semiconductor devices by reducing gate leak current and increasing withstanding voltage.
Implementation Method 1
the nitride semiconductor layer is formed at a growth rate of 12 nm/min or more using TMAl or TEAl and NH3 as precursors (material gases) by a MOVPE method
Data Source
AI summary
A compound semiconductor substrate includes a substrate, a channel layer provided over the substrate, a nitride semiconductor layer provided over the channel layer, and a barrier layer provided on the nitride semiconductor layer. The length of the c axis of the nitride semiconductor layer is 0.4990 nm or more.