Two-Layer AlN Single-Crystal Substrate for Chipping Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
AlN single-crystal substrates are susceptible to chipping during processing such as grinding, polishing, or cutting, leading to low yield and high defect rates.
Innovation Solution
An AlN single-crystal substrate with a two-layer structure is developed, where the first layer has a higher concentration of boron atoms (9.4×1018 cm−3 or more) compared to the second layer, with the second layer having a lower boron concentration (less than 7.0×1017 cm−3), along with controlled concentrations of carbon and oxygen atoms, resulting in reduced chipping during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If AlN single-crystal substrates are processed (ground, polished, or cut), then manufacturing is enabled, but chipping occurs leading to low yield
Solution Approach 1:
The patent applies local quality by creating a two-layer structure where the first layer (near surface) has high boron concentration (9.4×10^18 cm^-3 or more) to provide chipping resistance during processing, while the second layer (bulk) has low boron concentration (less than 7.0×10^17 cm^-3) to maintain ultraviolet transmittance. This spatial differentiation of impurity concentration allows each region to optimize for its specific function.
Solution Approach 2:
The patent changes the physical-chemical parameter of boron concentration distribution within the crystal structure. By controlling boron concentration to be at least 10 times higher in the first layer compared to the second layer, the material properties are modified locally to achieve both high chipping resistance during processing and high ultraviolet transmittance in the final product.
2Reliability
If impurity concentration is reduced to achieve high ultraviolet transmittance, then optical performance improves, but chipping resistance during processing deteriorates
Solution Approach 1:
The patent segments the single crystal into two functional layers based on boron concentration. The first layer (thickness 10 μm to 1 mm from surface) contains high boron concentration for mechanical strength and chipping resistance. The second layer (remaining bulk) contains low boron concentration for high ultraviolet transmittance. This segmentation resolves the contradiction by assigning different functional requirements to different spatial regions.
Solution Approach 2:
By locally concentrating boron impurities in the first layer near the surface, the patent creates a region with enhanced mechanical properties for chipping resistance, while the bulk second layer maintains low impurity content for optimal optical transmission. This localized impurity distribution allows simultaneous optimization of both mechanical and optical properties.
Data Source
AI summary
There is provided an AlN single-crystal substrate having a two-layer structure composed of an AlN single crystal as a whole, which is distinguishable into a first layer and a second layer in a thickness direction based on an impurity concentration. The AlN single-crystal substrate includes boron as an impurity, and a boron atom concentration in the first layer is 9.4×1018 cm−3 or more, and is at least 10 times a boron atom concentration in the second layer.