Joined Low-Resistivity Silicon Substrate for Nitride Semiconductor Warp Control
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Solution Overview
Problem
Existing substrates for electronic devices with nitride semiconductors grown on silicon substrates face challenges in suppressing warp due to differences in lattice constant and thermal expansion coefficients, especially when thick epitaxial layers are required for high breakdown voltage applications.
Innovation Solution
A substrate comprising multiple silicon single crystal substrates joined via a CZ method with a resistivity of 0.1 Ωcm or lower and a thickness of over 2000 μm, optionally bonded with a SiO2 film, to enhance strength and reduce stress, allowing for thicker nitride semiconductor film growth while minimizing warp.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an epitaxial layer is stacked thickly to enhance high breakdown voltage characteristics, then the breakdown voltage performance is improved, but a warp occurs in the wafer due to the difference in thermal expansion coefficient between the silicon substrate and the epitaxial layer
Solution Approach 1:
The substrate is divided into multiple silicon single crystal substrates that are joined together to form a thick substrate (more than 2000 μm). This segmentation approach allows the substrate itself to provide sufficient mechanical strength to suppress warp, while still enabling thick epitaxial layer growth for high breakdown voltage characteristics.
Solution Approach 2:
The invention changes the resistivity parameter of the silicon substrates to 0.1 Ωcm or lower, which significantly increases the strength of the substrates. This parameter change allows the substrate to resist warp even when thick epitaxial layers are grown, thereby maintaining both high breakdown voltage characteristics and wafer flatness.
2Strength
If a thick substrate is used to suppress warp, then the mechanical strength is improved, but the cost and complexity of substrate preparation increases
Solution Approach 1:
Multiple silicon single crystal substrates are joined together to form a thick substrate structure. This merging approach achieves the required mechanical strength and warp suppression without needing to prepare a single extremely thick substrate, which would be more complex and costly. The joined substrate structure distributes the mechanical load across multiple thinner substrates.
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 approach significantly reduces warp and enhances the strength of the substrate, making it suitable for high breakdown voltage applications by using low-resistivity CZ silicon substrates with controlled oxygen concentration, thereby improving the reliability and performance of nitride semiconductor films.
Implementation Method 1
the plurality of silicon single crystal substrates are produced by a CZ method and have a resistivity of 0.1 Ωcm or lower
Implementation Method 2
epitaxial growth by vapor deposition on a silicon substrate is employed
Implementation Method 3
due to stress caused by a difference in lattice constant or a difference in thermal expansion coefficient, an increase in warp and plastic deformation easily occur
Data Source
AI summary
A substrate for an electronic device, including a nitride semiconductor film formed on a joined substrate including a silicon single crystal, where the joined substrate has a plurality of silicon single crystal substrates that are joined and has a thickness of more than 2000 μm, and the plurality of silicon single crystal substrates are produced by a CZ method and have a resistivity of 0.1 Ωcm or lower. This provides: a substrate for an electronic device having a nitride semiconductor film formed on a silicon substrate, where the substrate for an electronic device can suppress a warp and can also be used for a product with a high breakdown voltage; and a method for producing the same.