Nitride Semiconductor Substrate Lamination for Lower Dislocation Density
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Solution Overview
Problem
The crystal quality of nitride semiconductor substrates is not adequately improved in conventional techniques, limiting their performance and applications.
Innovation Solution
A nitride semiconductor substrate with a (0001) plane as the closest low index crystal plane, featuring a laminated structure with low and high oxygen concentration regions, and a manufacturing method involving vapor phase growth with specific epitaxial growth steps to enhance crystal quality, including three-dimensional growth and flattening layers to reduce dislocation density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single crystal growth methods are used on (0001) plane base substrates, then substrate fabrication is simplified, but crystal quality remains inadequate with high dislocation density
Solution Approach 1:
The substrate is divided into multiple functional layers: a base substrate providing mechanical support, an intermediate layer with controlled dislocation structure, and a top crystal growth layer. This segmentation allows each layer to serve its specific function - the base substrate simplifies fabrication while the intermediate layer manages dislocations, resolving the contradiction between manufacturing simplicity and crystal quality.
Solution Approach 2:
An intermediate layer is introduced between the base substrate and the crystal growth layer. This intermediary layer acts as a mediator that captures and manages dislocations, preventing them from propagating to the top layer. This allows the use of simple (0001) plane base substrates while achieving high crystal quality in the final product.
2Manufacturing precision
If conventional growth methods are used, then manufacturing process is simple, but dislocation density remains high
Solution Approach 1:
The intermediate layer is prepared in advance with specific structural characteristics before crystal growth begins. This preliminary action creates a dislocation-managing foundation that simplifies the subsequent growth process, as the dislocation control mechanism is already in place rather than requiring complex in-situ control during growth.
Solution Approach 2:
Different regions of the substrate structure have different properties: the base substrate has simple (0001) plane orientation for easy fabrication, while the intermediate layer has specific dislocation density and orientation characteristics. This local differentiation allows simple manufacturing of the base while achieving precise dislocation control in the critical growth region.
3Manufacturing precision
If (0001) plane base substrates are used, then epitaxial growth is straightforward, but crystal quality improvement is limited
Solution Approach 1:
The laminated structure segments the substrate into distinct functional zones: the (0001) plane base substrate for straightforward epitaxial growth, and the intermediate layer for dislocation management. This segmentation maintains the simplicity of working with (0001) planes while adding crystal quality improvement through the intermediate layer's special structure.
Solution Approach 2:
The intermediate layer serves as an intermediary between the simple (0001) base substrate and the high-quality crystal growth requirement. It enables straightforward epitaxial growth on the base while simultaneously improving crystal quality by managing dislocations, thus resolving the contradiction between growth simplicity and quality improvement.
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 significantly improves the crystal quality of nitride semiconductor substrates, reducing dislocation density and enhancing their performance and reliability.
Implementation Method 1
a method for manufacturing a nitride semiconductor substrate using a vapor phase growth method, the method including: a step (a) of preparing a base substrate that is constituted by a single crystal of a group III nitride semiconductor... a step (b) of homoepitaxially growing a single crystal of a group III nitride semiconductor above the main surface such that the crystal becomes flat
Implementation Method 2
a step (c) of growing a three-dimensional growth layer by generating a plurality of recessed portions formed by inclined interfaces other than a (0001) plane in a surface of the homoepitaxially grown flat crystal, and gradually expanding the inclined interfaces as the crystal growth progresses
Data Source
AI summary
A nitride semiconductor substrate that has a diameter of 2 inches or more and includes a main surface for which the closest low index crystal plane is a (0001) plane. The ratio of FWHM1{10-12} to FWHM2{10-12} is 80% or more.