TRSOI Substrate Structure for Low Second Harmonic GaN RF Devices
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Solution Overview
Problem
Existing high-frequency devices using TR substrates face limitations in improving second harmonic characteristics due to the influence of silicon substrate resistivity and oxygen concentration, despite the use of a TRSOI substrate with a GaN layer.
Innovation Solution
A high-frequency device substrate is developed with an SOI structure, specifically a TRSOI substrate, where the SOI layer has a resistivity of 1k Ω·cm or more, a (111) crystal plane orientation, and an oxygen concentration of 14.8 ppma or less, which enhances the formation of a nitride semiconductor film, thereby improving high-frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TR substrate with high-resistivity silicon is used to prevent signal leakage, then signal isolation is improved, but second harmonic characteristics deteriorate due to silicon substrate influence
Solution Approach 1:
The substrate is divided into three distinct layers: a base substrate for mechanical support, a TR layer for signal isolation, and an SOI layer with controlled oxygen concentration for harmonic characteristic optimization. This segmentation allows each layer to independently fulfill its specific function without interfering with others.
Solution Approach 2:
The oxygen concentration is locally optimized in the SOI layer (14.8 ppma or less) while maintaining high resistivity (1k Ω·cm or more). This local quality control enables the substrate to simultaneously achieve good signal isolation and reduced second harmonic distortion, addressing the contradiction between reliability and harmful factors.
2Reliability
If the oxygen concentration in the SOI layer is reduced to improve high-frequency characteristics, then manufacturing complexity increases
Solution Approach 1:
The oxygen concentration parameter in the SOI layer is precisely controlled to be 14.8 ppma or less through optimized manufacturing parameters. This parameter change enables improved high-frequency characteristics while the patent provides specific manufacturing guidance to manage the associated complexity.
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
The substrate achieves further reduction in second harmonic distortion, reaching -95 dBm or better, compared to conventional limits of -91 dBm, by optimizing the SOI layer's resistivity and oxygen concentration.
Implementation Method 1
a trap rich layer formed on a base substrate and an SOI layer composed of a silicon single crystal are bonded via an oxide film
Implementation Method 2
a GaN layer or the like is epitaxially grown thereon to manufacture a high-frequency device
Data Source
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AI summary
The present invention is a high-frequency device substrate including an SOI substrate with a nitride semiconductor film formed thereon. The SOI substrate is a TRSOI substrate in which a trap rich layer formed on a base substrate and an SOI layer composed of a silicon single crystal are bonded via an oxide film. The SOI layer has a resistivity of 1k Ω·cm or more, a crystal plane orientation of (111), and an oxygen concentration of 14.8 ppma or less. Thereby, a high-frequency device substrate having excellent high-frequency characteristics and a method for producing the same are provided.