GaN Wafer Quality Control via Ammonothermal Ingot Segmentation
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Solution Overview
Problem
The high cost and time-consuming quality control processes in producing GaN wafers using hydride vapor phase epitaxy (HVPE) are exacerbated by the need to test each wafer individually, as wafers grown on heterogeneous substrates exhibit run-to-run fluctuation in characteristics, making it impractical for high-volume production.
Innovation Solution
The ammonothermal method is used to grow bulk GaN ingots, allowing wafers to be sliced from a single ingot, where test data from a subset of wafers can represent the properties of all wafers, reducing the need for individual testing through correlations based on distance from the seed material and polar orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each GaN wafer is tested individually using HVPE method, then quality control reliability is improved, but production time and cost increase significantly
Solution Approach 1:
The invention segments the quality control process by dividing wafers into groups based on their position relative to the seed material in the ammonothermal ingot. Instead of testing each wafer individually, representative wafers from each segment are tested, and results are extrapolated to other wafers in the same segment, thereby reducing testing workload while maintaining quality control reliability.
Solution Approach 2:
The invention performs preliminary characterization of the seed material before wafer production. By establishing the relationship between seed material properties and wafer properties in advance, the method enables prediction of wafer quality without individual testing, thus improving productivity while maintaining reliability.
2Measurement precision
If all wafers from an ingot are tested, then measurement precision is improved, but loss of time and resources increase
Solution Approach 1:
The invention applies local quality principle by recognizing that wafers at different positions in the ammonothermal ingot have different properties. Specifically, wafers from the same polar side (c-plane or m-plane) relative to the seed material exhibit similar characteristics. This allows selective testing of representative wafers from each local region rather than uniform testing of all wafers, reducing time loss while maintaining measurement precision for each local group.
3Ease of manufacture
If HVPE method is used to grow GaN films on heterogeneous substrates, then manufacturing flexibility is improved, but manufacturing precision deteriorates due to high defect rates
Solution Approach 1:
The invention changes the fundamental growth parameters by transitioning from heteroepitaxial growth on foreign substrates to ammonothermal growth that produces bulk single-crystal GaN ingots. This parameter change eliminates the lattice mismatch and thermal expansion coefficient differences that cause defects in heteroepitaxial growth, thereby improving manufacturing precision while maintaining ease of manufacture through the slicing process.
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 significantly reduces the time, labor, and cost associated with quality control by allowing representative testing of GaN wafers, ensuring consistent quality across wafers from the same ingot, thus enabling more efficient and cost-effective production.
Implementation Method 1
An ammonothermal method, which is a solution growth method using high-pressure ammonia as a solvent
Implementation Method 2
ammonothermal growth using a seed material
Data Source
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AI summary
The present invention discloses a new testing method of group Ill-nitride wafers. By utilizing the ammonothermal method, GaN or other Group Ill-nitride wafers can be obtained by slicing the bulk GaN ingots. Since these wafers originate from the same ingot, these wafers have similar properties/qualities. Therefore, properties of wafers sliced from an ingot can be estimated from measurement data obtained from selected number of wafers sliced from the same ingot or an ingot before slicing. These estimated properties can be used for product certificate of untested wafers. This scheme can reduce a significant amount of time, labor and cost related to quality control.