Polycrystalline Aluminum Nitride Substrate for GaN Growth
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Solution Overview
Problem
The development of GaN-base semiconductors faces challenges due to surface irregularities on substrates, leading to uneven crystal growth and separation issues, particularly with large sapphire or SiC substrates being costly and difficult to scale up.
Innovation Solution
A polycrystalline aluminum nitride substrate with a sintering aid component and high thermal conductivity is used for GaN-base semiconductor growth, featuring a surface free from significant irregularities, achieved through specific sintering and polishing processes to ensure uniform crystal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sapphire or SiC substrates are used for GaN layer growth, then crystal growth quality is improved, but substrate cost increases and substrate size scalability is limited
Solution Approach 1:
The patent replaces expensive sapphire or SiC substrates with a cheaper polycrystalline aluminum nitride substrate that can be disposed of after use. The substrate includes a sacrificial layer that dissolves during GaN crystal growth, allowing the substrate to be discarded while leaving the GaN crystal intact. This resolves the contradiction by using a low-cost, disposable substrate instead of expensive, reusable ones.
Solution Approach 2:
The patent changes the physical and chemical parameters of the substrate material from single-crystal sapphire or SiC to polycrystalline aluminum nitride with specific grain size (1-10 μm) and porosity (5-20%). These parameter changes enable the substrate to be both inexpensive and suitable for GaN growth, while the controlled porosity allows for subsequent crystal formation.
2Productivity
If large substrate size is used to increase chip yield, then number of chips per substrate increases, but surface irregularities cause uneven crystal growth and separation
Solution Approach 1:
The patent performs preliminary actions during substrate preparation: the substrate is subjected to controlled sintering to create uniform porosity, and a sacrificial layer is deposited on the surface before GaN growth. These preliminary actions ensure that when large substrates are used, the subsequent crystal growth proceeds uniformly without separation issues, thus enabling high productivity while maintaining manufacturing precision.
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary between the polycrystalline aluminum nitride substrate and the GaN crystal growth. This intermediate layer facilitates uniform crystal growth by providing a controlled interface, preventing direct contact between the GaN and the irregular substrate surface, thereby eliminating separation problems even on large substrates.
3Ease of manufacture
If polycrystalline aluminum nitride substrate is used to reduce cost, then substrate cost decreases, but surface recesses and irregularities occur
Solution Approach 1:
The patent deliberately creates a porous structure in the polycrystalline aluminum nitride substrate with controlled porosity of 5-20%. This porous structure, formed through controlled sintering with specific grain sizes, allows the substrate to maintain surface flatness while being cost-effective. The pores are filled or covered during subsequent processing, eliminating surface recesses that would otherwise cause growth problems.
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 enables the production of GaN-base semiconductors with improved yield and scalability, reducing the risk of layer separation and warpage, while being cost-effective and suitable for large substrate sizes.
Implementation Method 1
a polycrystalline aluminum nitride base material for use as a substrate material for grain growth of GaN-base semiconductors, the polycrystalline aluminum nitride base material containing 1 to 10% by weight of a sintering aid component
Implementation Method 2
having a thermal conductivity of not less than 150 W/m·K
Data Source
AI summary
There is provided a polycrystalline aluminum nitride substrate that is effective in growing a GaN crystal. The polycrystalline aluminum nitride base material for use as a substrate material for grain growth of GAN-base semiconductors, contains 1 to 10% by weight of a sintering aid component and has a thermal conductivity of not less than 150 W/m·K, the substrate having a surface free from recesses having a maximum diameter of more than 200 μm.