Epitaxial Substrate Surface Roughness Control for Leakage Current
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Solution Overview
Problem
The challenge is to suppress V pits in the buffer layer structure of epitaxial substrates to improve longitudinal leakage current characteristics in electronic devices, as a higher number of V pits correlates with increased leakage current.
Innovation Solution
An epitaxial substrate is created with a Si-based substrate, an AlN initial layer, and a buffer layer where the surface roughness Sa of the AlN initial layer is set to 4 nm or more, and the buffer layer includes an AlzGa1−zN layer with a surface roughness Sa of 0.6 nm or less, and a multilayer film composed of alternately stacked AlxGa1−xN and AlyGa1−yN layers with a surface roughness Sa of 0.3 nm or less, which helps in reducing V pits and enhancing longitudinal leakage current characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the surface roughness Ra of the silicon substrate is set to 0.2 to 1 nm, then the crystallinity of the group-III nitride semiconductor is improved, but the longitudinal leakage current characteristics deteriorate
Solution Approach 1:
The invention changes the surface roughness parameter from the conventional 0.2-1 nm range to a new range of 0.5-5 nm, specifically optimizing it to reduce V-pit formation while maintaining acceptable crystallinity. This parameter change resolves the contradiction by finding a new optimal point that balances both crystallinity and leakage current characteristics.
Solution Approach 2:
The invention applies different surface quality requirements to different regions and layers: the AlN buffer layer surface is optimized for flatness (0.5-5 nm roughness) to prevent V-pits, while the silicon substrate surface maintains standard polishing quality. This local differentiation allows each layer to be optimized for its specific function without compromising the other.
2Ease of manufacture
If a flat surface of the base is used for epitaxial growth, then the epitaxial growth process is simplified, but V pits form in the buffer layer structure increasing leakage current
Solution Approach 1:
The invention performs preliminary surface preparation of the AlN buffer layer to achieve a specific roughness range (0.5-5 nm) before epitaxial growth. This preliminary action prevents V-pit formation during subsequent growth without requiring complex modifications to the epitaxial process itself, thus maintaining ease of manufacture while improving reliability.
Solution Approach 2:
The invention introduces a new surface roughness parameter specification (0.5-5 nm) for the AlN buffer layer, which is different from both the silicon substrate surface and the ideal perfectly flat surface. This parameter change optimizes the surface properties to prevent V-pit formation while remaining compatible with standard epitaxial growth processes.
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 configuration effectively suppresses V pits in the buffer layer and improves longitudinal leakage current characteristics, leading to better performance in electronic devices.
Implementation Method 1
a method for producing a semiconductor epitaxial wafer with a GaN film formed on a Si substrate by epitaxial growth
Data Source
AI summary
An epitaxial substrate for electronic devices, including: a Si-based substrate; an AlN initial layer provided on the Si-based substrate; and a buffer layer provided on the AlN initial layer, wherein the roughness Sa of the surface of the AlN initial layer on the side where the buffer layer is located is 4 nm or more. As a result, an epitaxial substrate for electronic devices, in which V pits in a buffer layer structure can be suppressed and longitudinal leakage current characteristics can be improved when an electronic device is fabricated therewith, is provided.