GaN Single-Crystal Substrate Growth With Edge Metal Mask Ring
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Solution Overview
Problem
Existing GaN single-crystal substrate preparation methods using hydride vapor phase epitaxy (HVPE) face issues such as cladding, stress accumulation, and anisotropic growth at the edge, leading to reduced substrate quality and yield due to polycrystalline particle attachment and size reduction.
Innovation Solution
A method involving a metal mask ring is used to confine and control the growth of a GaN single-crystal sacrificial layer, followed by interlayer decoupling and diameter expansion, combined with chemico-mechanical trimming to obtain a stress-free self-supporting GaN single-crystal substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a graphite crucible with groove sidewall is used to restrict edge growth, then the GaN single-crystal thick film growth is confined, but polycrystalline GaN particles attach on the groove sidewall causing steady air flow damage and size reduction
Solution Approach 1:
The patent changes the material parameter of the mask from graphite to metal (such as molybdenum or tungsten), which fundamentally alters the interaction between the mask surface and GaN particles. The metal mask ring does not generate polycrystalline particles and maintains stable air flow, resolving the harmful attachment problem while preserving edge growth control
Solution Approach 2:
The patent introduces a sacrificial GaN layer that is intentionally grown and then removed. This disposable layer serves as a temporary structure during the growth process to enable subsequent diameter expansion, and is discarded after serving its purpose, thus solving the contradiction between maintaining diameter and achieving expansion
2Length of stationary object
If the GaN single-crystal thick film is grown to 100 μm thickness, then the substrate thickness is sufficient, but anisotropic growth at the edge causes cladding, stress accumulation, and unintentional doping
Solution Approach 1:
The patent performs preliminary actions by growing the GaN layer with the metal mask ring in place before removal. The mask ring prevents anisotropic edge growth during the critical early stages of thick film formation, ensuring uniform crystalline quality throughout the thickness development process
Solution Approach 2:
The metal mask ring acts as an intermediary object that mediates the growth process. It provides a physical boundary that prevents direct interaction between the growing GaN edges and the environment, eliminating the anisotropic growth pathway while allowing controlled uniform growth
3Manufacturing precision
If the metal mask ring is used to confine GaN single-crystal sacrificial layer growth, then edge anisotropic growth is prohibited, but the substrate diameter is restricted by the mask ring inner diameter
Solution Approach 1:
The patent uses the metal mask ring for preliminary confinement during the growth of the sacrificial layer, ensuring uniform edge quality. After this preliminary phase, the mask ring is removed and the sacrificial layer is etched away, allowing subsequent diameter expansion without the mask constraint
Solution Approach 2:
The sacrificial GaN layer serves as a disposable temporary structure that enables the diameter expansion process. It is grown under confinement, then removed to allow the final substrate to expand beyond the original mask ring diameter, achieving both quality and size goals
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 method improves crystalline quality and prevents mismatch stress, maintaining substrate diameter and thickness, enhancing the curvature radius and yield of the GaN single-crystal substrate.
Implementation Method 1
the metal mask ring catalyzes decomposition of the ammonia, thereby blocking attached growth of nitride on the metal mask ring
Implementation Method 2
epitaxially growing the GaN single-crystal sacrificial layer in the confined manner on the front surface of the composite epitaxial substrate in an HVPE chamber with HVPE
Implementation Method 3
a gallium (Ga) metal atom provided by an III-group source chemically reacts with a nitrogen (N) atom provided by a nitrogen source (ammonia or NH3)
Implementation Method 4
introducing a thermal stress in a horizontal direction through a time-domain temperature gradient, such that a binding force between the nitrogen-lattice polar GaN epitaxial thin film and the single-crystal graphene, and a binding force between the metal-lattice polar GaN single-crystal template and the single-crystal graphene are greater than an interlayer binding force of the single-crystal graphene
Data Source
AI summary
The present disclosure provides a method for preparing a gallium nitride (GaN) single-crystal substrate with an edge metal mask technology. The method includes: preparing a metal mask ring on a composite epitaxial substrate, epitaxially growing a GaN single-crystal sacrificial layer in a confined manner, performing separation with interlayer decoupling of single-crystal graphene through an in-situ temperature gradient method to obtain a self-supporting GaN single-crystal sacrificial layer, epitaxially growing a GaN single-crystal thick film in a diameter expanded manner, and performing chemico-mechanical trimming on the GaN single-crystal thick film to obtain a stress-free self-supporting GaN single-crystal substrate. The metal mask ring is compatible with the GaN single-crystal preparation process (hydride vapor phase epitaxy (HVPE)), and efficiently catalyzes decomposition reaction of the nitrogen source. While prohibiting edge growth of the GaN single-crystal thick film, the present disclosure improves a crystalline quality of the GaN single-crystal substrate.