Transfer-Bonding Light Emitting Devices for Micro-Displays
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Solution Overview
Problem
The challenge in monolithic micro-display technology is the difficulty in growing light emitting layers with different lattice constants on a single substrate and the low efficiency of color conversion materials in existing colorizing techniques for inorganic light emitting diodes, which affects brightness and display quality.
Innovation Solution
A transfer-bonding method for light emitting devices involves a first substrate with an elastic interlayer and a second substrate with a mask layer, where light emitting devices are bonded and then separated, allowing parts of the device layers to be transferred to the second substrate, enabling efficient embedding and bonding without excessive pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If light emitting layers with different lattice constants are grown on a single substrate, then colorizing capability is achieved, but growth difficulty increases due to lattice mismatch
Solution Approach 1:
The patent divides the light emitting device structure into separate layers: a first light emitting layer grown on a first substrate, and a second light emitting layer transferred from a second substrate. This segmentation allows each layer to be grown on substrates optimized for its specific lattice constant, avoiding the growth difficulties that would arise from attempting to grow both layers on a single substrate with mismatched lattice constants.
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary between the second light emitting layer and the second substrate. This sacrificial layer facilitates the growth of the second light emitting layer on the second substrate, and is subsequently removed to enable clean transfer of the second light emitting layer to the first substrate, mediating the complex process of transferring between substrates with different lattice structures.
2Adaptability or versatility
If color conversion materials are used for colorizing, then color variety is achieved, but conversion efficiency and coating uniformity deteriorate
Solution Approach 1:
The patent extracts the color generation function from color conversion materials and implements it directly through light emitting layers with different lattice constants that emit different wavelengths of light inherently. This eliminates the need for color conversion materials, thereby resolving the issues of low conversion efficiency and coating uniformity while maintaining color variety.
3Illumination intensity
If light emitting devices are transferred to circuit substrate, then brightness and display quality are enhanced, but bonding precision requirement increases
Solution Approach 1:
The patent performs preliminary alignment and bonding of the first light emitting layer to the first substrate before transferring the second light emitting layer. This preliminary action establishes a stable foundation that reduces the precision requirements for subsequent transfer operations, as the first layer is already securely positioned on the circuit substrate.
Solution Approach 2:
The sacrificial layer serves as a mediator that simplifies the transfer process. By using this intermediate layer, the bonding precision requirements are reduced because the transfer can be achieved through simple mechanical separation rather than requiring high-precision re-bonding operations. The sacrificial layer acts as a temporary placeholder that is easily removed after transfer.
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 enhances the brightness and display quality of monolithic micro-displays by efficiently transferring light emitting devices to a circuit substrate, addressing the limitations of existing colorizing technologies and ensuring precise bonding and uniformity.
Implementation Method 1
providing a first substrate having an elastic interlayer formed thereon; bonding the first substrate and the second substrate, such that parts of the device layers are bonded with the area of the second substrate exposed by the mask layer and the light emitting devices are pressed and embedded in the elastic interlayer by the second substrate
Data Source
AI summary
A transfer-bonding method for light emitting devices including following steps is provided. A plurality of light emitting devices is formed over a first substrate and is arranged in array, wherein each of the light emitting devices includes a device layer and an interlayer sandwiched between the device layer and the first substrate. A protective layer is formed over the first substrate to selectively cover parts of the light emitting devices, and other parts of the light emitting devices are uncovered by the protective layer. The device layers uncovered by the protective layer are bonded with a second substrate. The interlayers uncovered by the protective layer are removed, so that parts of the device layers uncovered by the protective layer are separated from the first substrate and are transfer-bonded to the second substrate.