III-Nitride Epitaxial Layer Separation Without Grind Damage
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Solution Overview
Problem
Existing methods for separating and transferring semiconductor epitaxial material from non-crystalline substrates, such as gallium nitride (GaN) engineered substrates, face challenges due to high thermal boundary resistance and substrate cracking, particularly when using silicon carbide substrates.
Innovation Solution
A method and device for separating and transferring III-nitride epitaxial material from a non-crystalline substrate, involving steps like grinding, chemical mechanical polishing, and bonding to a carrier substrate, while minimizing substrate damage and thermal boundary resistance, using techniques like ultrasonic vibration assisted grinding and chemical mechanical polishing to ensure the epitaxial layer remains free of grind damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional grinding methods are used to separate epitaxial material from non-crystalline substrate, then separation can be achieved, but subsurface defects and grind damage occur in the epitaxial layer
Solution Approach 1:
The patent applies ultrasonic vibration during the grinding process to reduce subsurface defects. The ultrasonic vibrations disrupt the formation of grind damage and subsurface cracks by introducing high-frequency mechanical oscillations that prevent defect propagation into the epitaxial layer, thereby improving epitaxial layer quality while maintaining separation effectiveness.
Solution Approach 2:
The patent replaces conventional mechanical grinding with chemical mechanical polishing (CMP) to eliminate subsurface defects. CMP uses a combination of chemical etching and mechanical polishing to remove material, which prevents the formation of grind damage and subsurface cracks that occur with traditional mechanical grinding, thus producing a defect-free epitaxial layer.
2Strength
If silicon carbide substrate is used for GaN growth, then thick GaN layers can be grown without cracking, but high thermal boundary resistance occurs at the interface
Solution Approach 1:
The patent introduces an aluminum nitride (AlN) nucleation layer as an intermediary between the silicon carbide substrate and the GaN epitaxial layer. This AlN layer serves as a thermal conduit that reduces thermal boundary resistance while maintaining the crack resistance provided by the silicon carbide substrate, thus resolving the thermal interface problem without sacrificing mechanical strength.
Solution Approach 2:
The patent creates a composite substrate structure consisting of silicon carbide substrate with an aluminum nitride nucleation layer. This composite material combines the crack resistance of silicon carbide with the superior thermal conductivity of aluminum nitride, achieving both mechanical strength and low thermal boundary resistance in a single integrated substrate system.
3Reliability
If engineered substrate with multiple layers is used, then low defect density GaN can be achieved, but complex separation process is required
Solution Approach 1:
The patent extracts and removes the non-crystalline substrate and engineered substrate layers from the final product, leaving only the high-quality GaN epitaxial layer on the desired carrier substrate. This extraction approach maintains the low defect density benefits of the engineered substrate during growth while eliminating the need to retain the complex multi-layer structure in the final device.
Solution Approach 2:
The patent performs preliminary bonding of the GaN epitaxial layer to the carrier substrate during the growth process itself, before the separation step. This preliminary action ensures that the epitaxial layer is already securely attached to its final substrate, simplifying the subsequent separation process and reducing the complexity of handling the multi-layer engineered substrate structure.
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 effectively separates and transfers III-nitride epitaxial material with minimal subsurface defects and crack density, enabling further processing and integration with carrier substrates like polycrystalline diamond or silicon carbide, reducing thermal boundary resistance and preserving the material's integrity.
Implementation Method 1
using techniques like ultrasonic vibration assisted grinding
Implementation Method 2
chemical mechanical polishing to ensure the epitaxial layer remains free of grind damage
Implementation Method 3
bonding to a carrier substrate
Data Source
AI summary
A method, wherein a III-nitride-on-engineered substrate is provided. The III-nitride-on-engineered substrate includes a III-nitride epitaxial material. The III-nitride epitaxial material includes a frontside, a backside, and a III-nitride epitaxial region free of grind damage. The III-nitride-on-engineered substrate includes an engineered substrate on the backside of the III-nitride epitaxial material. The engineered substrate includes a non-crystalline substrate. The engineered substrate is removed from the backside of the III-nitride epitaxial material, thereby exposing the III-nitride epitaxial region free of grind damage.