AlGaN Nucleation Layer for GaN-on-SiC Bow and Surface Control
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Solution Overview
Problem
The challenge is to control the formation of a gallium nitride epitaxial layer on a silicon carbide substrate to achieve good geometric quality, as direct growth leads to three-dimensional growth and surface roughness, and existing buffer layers like aluminum nitride have high resistance and uncontrolled bow.
Innovation Solution
A semiconductor structure is formed with a nucleation layer of aluminum gallium nitride (AlGaN) on a silicon carbide substrate, where the thickness and aluminum content of the AlGaN layer are carefully controlled to facilitate a 2D growth of the gallium nitride layer, reducing stress and bow within an acceptable range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If gallium nitride is directly grown on the silicon carbide substrate, then the growth process is simplified, but the gallium nitride surface becomes rough due to three-dimensional growth
Solution Approach 1:
The patent introduces a nucleation layer composed of AlGaN with aluminum content of 10-30% as an intermediary between the silicon carbide substrate and the gallium nitride epitaxial layer. This intermediate layer facilitates two-dimensional growth of gallium nitride, preventing surface roughness while maintaining process feasibility.
2Ease of manufacture
If aluminum nitride is used as a buffer layer, then the gallium nitride growth is facilitated, but the layer exhibits high resistance and uncontrolled bow
Solution Approach 1:
The patent changes the material composition parameter by using AlGaN with specifically controlled aluminum content (10-30%) instead of pure aluminum nitride. This parameter adjustment enables both facilitated gallium nitride growth and controllable bow within -25 μm to +25 μm, while also reducing resistance compared to aluminum nitride buffers.
3Manufacturing precision
If the aluminum content in AlGaN is increased, then the bow control is improved, but the resistance value increases
Solution Approach 1:
The patent optimizes the aluminum content parameter within the specific range of 10-30% to achieve the best balance between bow control and resistance. This parameter optimization ensures bow is controlled within -25 μm to +25 μm while maintaining lower resistance compared to higher aluminum content buffers like aluminum nitride.
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 allows for the continuous growth of the AlGaN layer in a 2D form, enabling the subsequent formation of a gallium nitride epitaxial layer with lower stress and improved geometric quality, with bow controlled within a suitable range, enhancing the semiconductor structure's performance.
Implementation Method 1
To grow a gallium nitride (GaN) epitaxial layer on a silicon carbide (SiC) substrate, it is usually necessary to form an aluminum nitride as a buffer layer or a wetting layer in between the silicon carbide substrate and the gallium nitride epitaxial layer to facilitate the growth of gallium nitride
Data Source
AI summary
A semiconductor structure includes a silicon carbide (SiC) substrate, a nucleation layer and a gallium nitride (GaN) layer. The silicon carbide layer has a first thickness T1. The nucleation layer is located on the silicon carbide layer and has a second thickness T2. The nucleation layer is made of AlGaN (AlGaN), and the second thickness T2 fulfills a thickness range of T1*0.002% to T1*0.006%. The gallium nitride layer is located on the nucleation layer and is separated from the silicon carbide substrate.