AlGaInP Micro-LED Structure for Crack-Resistant LLO Transfer
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Solution Overview
Problem
AlGaInP-based LEDs are mechanically fragile and prone to die cracking during the laser lift-off (LLO) step due to their low mechanical strength and vulnerability to stress, with existing techniques failing to address this issue effectively.
Innovation Solution
A micro-LED structure with an AlGaInP-based active layer bonded to a transparent substrate using an adhesive or bonding material that is transparent to the emission wavelength and laser light, with the long-side direction of the outer shape shifted from the crystal orientation to prevent cracking, and the use of benzocyclobutene as the adhesive for reliable LLO treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If AlGaInP-based LEDs are used for micro-LED displays, then the emission wavelength and color characteristics are improved, but the mechanical strength decreases and die cracking occurs during LLO transfer
Solution Approach 1:
The patent changes the crystal orientation parameter from the conventional <100> direction to the <110> direction. This parameter change fundamentally alters the mechanical properties of the AlGaInP-based LED, significantly improving mechanical strength and eliminating die cracking during LLO transfer while preserving the desired emission wavelength and color characteristics.
2Ease of manufacture
If LLO transfer is performed on AlGaInP-based micro-LEDs, then the transfer capability is improved, but die cracking occurs due to stress concentration at step portions
Solution Approach 1:
The patent changes the crystal orientation parameter to <110>, which fundamentally improves the mechanical strength and stress distribution throughout the device structure. This parameter change eliminates the root cause of die cracking during LLO transfer, enabling reliable transfer of AlGaInP-based micro-LEDs without damage.
3Device complexity
If the long-side direction of the outer shape aligns with the crystal orientation of <100>, then the device structure is simplified, but the device becomes highly prone to cracking due to cleavability of the crystal
Solution Approach 1:
The patent changes the crystal orientation parameter from <100> to <110>, which fundamentally alters the cleavage behavior and mechanical strength characteristics. This parameter change eliminates the alignment between the long-side direction and crystal orientation that causes cracking, while maintaining reasonable device structure complexity.
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 proposed structure significantly reduces die cracking during the LLO step by enhancing the mechanical strength of the micro-LEDs, allowing for successful transfer to a desired substrate without damage.
Implementation Method 1
an adhesive that is transparent to the emission wavelength and absorbs the laser light for LLO transfer
Implementation Method 2
a transparent substrate transparent to both an emission wavelength and a laser light for LLO transfer
Data Source
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AI summary
The present invention is a micro-LED structure including a light emitting device structure having an active layer composed of (AlyGa1-y)xIn1-xP (0.4≤x≤0.6, 0≤y≤0.5), the light emitting device structure being bonded to a transparent substrate transparent to both an emission wavelength and a laser light for LLO transfer by an adhesive that is transparent to the emission wavelength and absorbs the laser light for LLO transfer or a bonding material that is transparent to the emission wavelength and absorbs the laser light for LLO transfer, in which the light emitting device structure is device isolated, the light emitting device structure, which is device isolated, has at least two electrodes of different polarities on one surface, and a long-side direction of an outer shape of the light emitting device structure, which is device isolated, in a plan view does not align with a crystal orientation of <110>. This provides the micro-LED structure in which cracking of the micro-LED structure can be reduced or avoided when transfer is performed in the LLO step in the micro-LED structure in which a light emitting device structure having an AlGaInP-based active layer is bonded to a transparent substrate via the adhesive or the bonding material.