Micro LED Laser Release via Ablation Layer Aperture
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Solution Overview
Problem
The Direct Transfer Method (DTM) for manufacturing micro LEDs faces yield limitations due to insufficient ablation force, which can result in micro-LEDs not detaching properly from the donor silicon wafer, leading to breakage or incomplete transfer, requiring precise sizing of ablation layer thickness and GaN edge strength, making consistent release challenging.
Innovation Solution
The structure and formation of layers are altered to decrease the portion of the GaN stem attached to the nucleation layer, reducing the required detachment force while increasing the force absorption by the micro-LED body, allowing for consistent release and improved yield by positioning the ablation layer directly beneath the GaN stem and minimizing the contact area between the micro-LED and nucleation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ablation layer thickness is increased to provide sufficient detachment force, then the release reliability improves, but the manufacturing precision requirement increases due to the need for precise sizing
Solution Approach 1:
The patent changes the physical state of the ablation layer by transforming it into a gas phase through laser ablation, converting the detachment mechanism from mechanical force to thermal expansion and gas pressure. This allows sufficient detachment force to be generated without requiring precise control of the ablation layer thickness, as the gas expansion provides self-regulating pressure that reliably detaches the micro-LED array.
Solution Approach 2:
The ablation layer undergoes a phase transition from solid to gas when exposed to laser energy. This phase transition generates rapid volume expansion and pressure buildup that provides the necessary detachment force. The phase change mechanism ensures reliable release without requiring precise dimensional control of the ablation layer, as the gas expansion naturally provides sufficient force.
2Ease of operation
If the contact area between micro-LED and nucleation layer is minimized to reduce detachment force requirement, then the release ease improves, but the manufacturing complexity increases due to precise positioning requirements
Solution Approach 1:
The ablation layer is pre-formed in direct contact with the nucleation layer before the micro-LED array is grown. This preliminary positioning ensures that when laser ablation occurs, the generated gas pressure is immediately applied to the interface between the micro-LED array and nucleation layer, providing efficient detachment without requiring complex real-time positioning during the release process.
Solution Approach 2:
The ablation layer serves as an intermediary between the laser energy source and the micro-LED array. It converts laser energy into gas pressure that acts as a mediator to detach the micro-LED array from the nucleation layer. This intermediary mechanism simplifies the release process by providing a uniform detachment force across the entire array without requiring precise individual positioning.
3Use of energy by moving object
If the GaN stem attachment to nucleation layer is decreased to reduce detachment force, then the release energy requirement decreases, but the micro-LED structural integrity may be compromised
Solution Approach 1:
The patent segments the GaN structure into a stem portion that remains attached to the nucleation layer and a body portion that is detached. The stem acts as a structural anchor that maintains integrity during the ablation process, while the body is released. This segmentation allows reduced overall attachment area for easier detachment while preserving the structural strength of the critical stem region.
Solution Approach 2:
The ablation layer is positioned to selectively affect specific regions of the GaN structure. The laser ablation is localized to the interface between the ablation layer and nucleation layer, providing detachment force precisely where needed without compromising the overall structural integrity of the GaN stem. This local quality approach reduces detachment energy requirements while maintaining strength.
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 approach enhances the yield of micro LEDs by reducing the need for precise layer sizing and increasing tolerance for variations in layer thickness, ensuring consistent and efficient detachment during the ablation process.
Implementation Method 1
Ablation of the ablation layer is performed to detach the array of micro-LEDs from the nucleation layer
Implementation Method 2
the ablation layer... to a gas phase, the expansion of which detaches the array of micro-LEDs
Data Source
AI summary
Methods and systems for improving the yield of laser ablation of semiconductor devices, such as micro-LEDs, in a direct transfer method are described. In the disclosed embodiments, an ablation layer is used to mask a nucleation layer on a donor substrate, with an aperture provided to allow epitaxial growth of a semiconductor structure. The aperture size is selected as the minimum necessary to ensure proper epitaxial growth. Layers disposed above the ablation layer may have larger apertures to that a portion of the semiconductor structure stem overlies the ablation layer, allowing a greater force generated during the ablation process to be directed against the semiconductor structure, improving the likelihood of separation of the structure from the donor substrate. Other embodiments are described.