GaN Substrate Tiling for Low Dislocation Density
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Solution Overview
Problem
Current methods fail to efficiently produce large-area non-polar or semi-polar GaN substrates with low dislocation density and few crystal regions, limiting their application in semiconductor devices.
Innovation Solution
A GaN substrate with a diameter of 2 inches or more is produced using a tiling method with a reduced number of crystal regions, specifically 4 or fewer, and a single crystal region, by aligning seed substrates in the c-axis direction and growing a GaN crystal using an ammonothermal method, resulting in lower dislocation density and fewer defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HVPE method is used to grow bulk GaN crystal on C-plane template, then crystal quality is improved, but substrate area is limited to several mm or less
Solution Approach 1:
The invention divides the large-area substrate production into multiple smaller seed substrates (e.g., 4 substrates of 50mm diameter arranged in a 2x2 pattern) that are grown separately by HVPE, then tiles them together to form a larger aggregate seed for subsequent ammonothermal growth, achieving both high crystal quality and large substrate area
Solution Approach 2:
The invention employs a nested growth strategy where small HVPE-grown seed substrates are embedded within a larger ammonothermal growth process, which in turn produces the final large-area bulk GaN crystal, allowing each process to operate at its optimal scale
2Area of stationary object
If tiling method with aggregate seeds is used to increase substrate area, then substrate area is improved, but dislocation density increases to 10^6-10^7 cm^-2
Solution Approach 1:
The invention changes the growth parameters by using ammonothermal method instead of HVPE for the main growth process, operating at lower temperatures (600-700°C) and different pressure conditions, which reduces dislocation multiplication and enables large-area growth with dislocation density below 10^6 cm^-2
Solution Approach 2:
The invention creates a composite growth system combining HVPE-grown seed substrates with ammonothermal growth process, where the seed provides high-quality initial crystal structure and the ammonothermal process provides low-dislocation large-area growth
3Stability of the object's composition
If number of crystal regions is reduced to 4 or fewer, then crystal uniformity is improved, but production complexity increases
Solution Approach 1:
The invention performs preliminary arrangement and bonding of seed substrates in the desired configuration (e.g., 2x2 pattern forming 4 crystal regions) before the main ammonothermal growth process, ensuring that the final substrate will have the target number of crystal regions and uniformity without requiring complex post-processing
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 enables the production of high-quality GaN substrates with reduced dislocation density and fewer crystal regions, enhancing the yield and reliability of semiconductor devices by minimizing defects and improving crystal uniformity.
Implementation Method 1
growing a GaN crystal using an ammonothermal method
Implementation Method 2
A GaN crystal is caused to precipitate on a seed, using ammonia in a supercritical or subcritical state as a solvent
Implementation Method 3
A bulk GaN crystal that constitutes one continuous layer is epitaxially grown, by a vapor phase method, on the aggregate seed
Implementation Method 4
epitaxially grown, by a vapor phase method
Implementation Method 5
bulk GaN crystal having been grown in the c-axis direction, on a C-plane GaN template, by HVPE
Data Source
AI summary
A disc-like GaN substrate is a substrate produced by a tiling method and having an angel between the normal line and m-axis on the main surface of the substrate of 0 to 20° inclusive and a diameter of 45 to 55 mm, to 4 or less. In a preferred embodiment, a disc-like GaN substrate has a first main surface and a second main surface that is opposite to the first main surface, and which has an angle between the normal line and m-axis on the first main surface of 0 to 20° inclusive and a diameter of 45 mm or more. The disc-like GaN substrate comprises at least four crystalline regions each being exposed to both of the first main surface and the second main surface, wherein the four crystalline regions are arranged in line along the direction of the orthogonal projection of c-axis on the first main surface.