Optical Device Layer Transfer via Laser Ablation and Ultrasonic Separation
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Solution Overview
Problem
The transfer rate of micro LEDs during laser lift-off is reduced, posing a challenge in efficiently transferring optical device layers from an optical device wafer to a transfer member.
Innovation Solution
A method involving transfer member bonding, buffer layer breaking, adhesive removing, and second optical device layer transferring steps, where a pulsed laser beam is used to break buffer layers and ultrasonic vibration separates the epitaxy substrate, allowing for efficient transfer of optical device layers to a mounting substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a laser lift-off is performed on micro LEDs, then the optical device layer can be separated from the sapphire substrate, but the transfer rate of each LED to the transfer member is reduced
Solution Approach 1:
The invention divides the optical device wafer into multiple chip-sized optical device layers and processes them in batches. By separating the laser lift-off process into stages (first transferring stacked layers, then removing adhesive to project individual layers), it maintains high transfer rates while ensuring complete transfer. This segmentation approach resolves the contradiction by processing multiple devices simultaneously rather than one-by-one.
Solution Approach 2:
The invention applies adhesive to fill spacing between optical device layers before the laser lift-off process. This preliminary action ensures that during the laser separation, the adhesive layer is already in place to receive and hold the optical device layers, preventing loss or misalignment and ensuring complete transfer to the transfer member.
2Reliability
If adhesive is used to bond the transfer member, then the optical device layers can be transferred, but the adhesive fills the spacing between adjacent optical device layers
Solution Approach 1:
The adhesive is applied in advance to fill the spacing between optical device layers before the laser lift-off. This preliminary positioning ensures stable transfer during the process, while the excess adhesive remaining after transfer is subsequently removed to facilitate further processing. The preliminary action ensures transfer stability without permanently compromising ease of operation.
Solution Approach 2:
The invention intentionally allows excess adhesive to remain after the transfer process, then removes it in a subsequent step. The adhesive serves its primary function of enabling stable transfer, then is discarded (removed) to restore ease of operation for subsequent processing. This temporary use and removal resolves the contradiction between transfer stability and processing ease.
3Productivity
If the optical device layers are transferred in stacked form, then the transfer rate increases, but the individual layers cannot be accessed for mounting
Solution Approach 1:
The invention implements a two-stage separation process: first, optical device layers are transferred in stacked form to maintain high transfer rate; second, adhesive is removed to project individual layers from the stack, making them accessible for mounting. This segmentation of the transfer and access functions resolves the contradiction by achieving both high productivity and ease of operation in sequence.
Solution Approach 2:
The stacked transfer is performed as a preliminary action to efficiently move multiple layers at once. After this preliminary high-rate transfer, the adhesive removal step individually accesses each layer. The preliminary stacked transfer ensures high productivity, while the subsequent individual projection ensures ease of operation for mounting.
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 effectively suppresses the reduction in transfer rate of optical device layers, enhancing the efficiency and accuracy of the transfer process.
Implementation Method 1
a pulsed laser beam having a transmission wavelength to the epitaxy substrate and an absorption wavelength to the buffer layers, to the buffer layers from a back surface of the epitaxy substrate
Implementation Method 2
a pulsed laser beam having a transmission wavelength to the epitaxy substrate and an absorption wavelength to the buffer layers
Implementation Method 3
separating the epitaxy substrate from the optical device layers to thereby transfer the optical device layers which have been stacked on the epitaxy substrate to the transfer member
Data Source
AI summary
A transferring method of transferring a plurality of optical device layers includes a transfer member bonding step, a buffer layer breaking step, a first optical device layer transferring step, an adhesive removing step, and a second optical device layer transferring step. In the transfer member bonding step, an optical device wafer and a transfer member are bonded to each other through an adhesive, and each spacing between adjacent ones of the optical device layers of the optical device wafer which each have been divided in a chip size is filled with the adhesive. In the adhesive removing step, at least part of the adhesive with which each spacing between the adjacent ones of the optical device layers has been filled is removed such that the optical device layers which have been embedded in an adhesive layer in the transfer member bonding step project from the adhesive layer.