Nitride Crystal Seed Substrate Porous Intermediate Layer Peeling
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Solution Overview
Problem
Existing methods for growing nitride crystal substrates face challenges in stabilizing the regrowth layer and easily peeling it off, particularly due to difficulties in forming uniform TiN layers and GaN layers with voids, which limits the production of large-area GaN crystal substrates.
Innovation Solution
A seed substrate is developed with a base substrate, an intermediate layer of n-type group III nitride crystal, and a cover layer with a lower carrier concentration, where the intermediate layer is made porous through dislocations in the cover layer using an electrochemical process, allowing for stable regrowth and easy peeling of the regrowth layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an electrochemical process is performed to form voids in the intermediate layer, then the regrowth layer can be peeled off easily, but the surface condition of the cover layer deteriorates (increased roughness)
Solution Approach 1:
The intermediate layer is designed to be porous with voids formed by the electrochemical process. These voids act as separation interfaces that enable easy peeling of the regrowth layer while the cover layer maintains its structural integrity and surface flatness
Solution Approach 2:
The electrochemical process selectively affects only the intermediate layer to create voids, while the cover layer maintains its original flat surface condition. This localized modification allows peeling ease without compromising the surface quality of the cover layer
2Ease of operation
If TiN layers and GaN layers with voids are formed to enable peeling, then peeling becomes possible, but the manufacturing complexity increases
Solution Approach 1:
The carrier concentration of the intermediate layer is specifically optimized to be higher than that of the cover layer. This parameter difference enables selective electrochemical etching of the intermediate layer to form voids, providing a controlled method to achieve peeling without complex multi-layer structures
Solution Approach 2:
The intermediate layer serves as a mediator between the base substrate and the cover layer. By making this intermediate layer porous through electrochemical process, it facilitates the peeling function while keeping the overall structure relatively simple
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 method enables the stable growth and easy peeling of the regrowth layer, resulting in a nitride crystal substrate with improved crystallinity and large-area coverage, overcoming the limitations of previous techniques.
Implementation Method 1
making the intermediate layer porous through dislocations in the cover layer by performing an electrochemical process
Implementation Method 2
making the intermediate layer porous through dislocations in the cover layer by performing an electrochemical process
Implementation Method 3
epitaxially growing a regrowth layer comprising group III nitride crystal, on the cover layer
Data Source
AI summary
To easily obtain a nitride crystal substrate. A seed substrate for nitride crystal growth includes: a base substrate; an intermediate layer provided above the base substrate and including n-type group III nitride crystal; and a cover layer provided on the intermediate layer and including group II nitride crystal having a carrier concentration lower than that of the intermediate layer, wherein the intermediate layer is porous, a surface of the cover layer has an arithmetic mean roughness of 1.0 nm or less, and the surface of the cover layer has a root mean square roughness of 2.0 nm or less, the arithmetic mean roughness and the root mean square roughness being values obtained when the surface of the cover layer is observed with an atomic force microscope in a field of view of 5 μm square.