LED Wafer Transfer Alignment Using Hierarchical Alignment Keys
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Solution Overview
Problem
Current methods for manufacturing display devices face challenges in achieving accurate alignment and efficient transfer of light emitting diodes (LEDs), leading to increased process time and cost, and reduced productivity due to alignment errors and complex processes.
Innovation Solution
The method involves using wafers with additional alignment keys to improve alignment accuracy during the primary and secondary transfer processes, allowing for precise alignment and transfer of LEDs onto a donor substrate and subsequently onto a display panel, utilizing different sized alignment keys to facilitate accurate positioning and reduce errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional transfer processes are used for LEDs, then the manufacturing process is simpler, but alignment accuracy deteriorates leading to increased errors
Solution Approach 1:
The patent divides the alignment system into multiple hierarchical levels: wafer-level alignment keys for initial positioning, donor substrate alignment keys for transfer alignment, and pixel-level alignment keys for final positioning. This segmentation allows each level to handle specific alignment tasks, improving overall accuracy without requiring a single complex alignment system.
Solution Approach 2:
The patent introduces alignment keys as intermediary reference elements that mediate between different transfer stages. These alignment keys serve as common reference points that enable precise alignment during wafer-to-donor transfer and subsequent donor-to-panel transfer, acting as intermediaries that bridge different alignment systems.
2Manufacturing precision
If multiple transfer processes are used for LEDs, then alignment coverage is improved, but process time increases
Solution Approach 1:
The patent performs preliminary alignment key positioning during the wafer fabrication process, so that alignment keys are already in place before the transfer process begins. This preliminary action eliminates the need for time-consuming alignment key installation during transfer operations, reducing process time while maintaining alignment coverage.
Solution Approach 2:
The patent combines multiple alignment functions into a unified alignment key system that serves both wafer-to-donor transfer and donor-to-panel transfer operations. By merging these alignment functions into common reference elements, the system reduces the number of separate alignment operations required, thereby reducing total process time.
3Manufacturing precision
If conventional alignment methods are used, then process steps are fewer, but alignment error distribution increases
Solution Approach 1:
The patent segments the alignment error sources into distinct categories handled by different alignment keys: wafer-level keys handle gross positioning errors, donor substrate keys handle transfer errors, and pixel-level keys handle fine positioning errors. This segmentation allows each alignment key to optimize for specific error types, improving overall error distribution without requiring a single complex alignment mechanism.
4Manufacturing precision
If additional alignment keys are added to wafers, then alignment accuracy improves, but wafer complexity increases
Solution Approach 1:
The patent designs alignment keys with multi-functionality, where the same alignment key structure serves multiple purposes: providing mechanical reference for alignment, enabling optical detection, and serving as transfer targets. This universality allows the system to achieve high alignment accuracy without adding numerous separate components, thereby limiting the increase in wafer structure complexity.
Data Source
AI summary
A method of manufacturing a display device is disclosed. The method comprisesaligning a first wafer with a donor substrate, the first wafer including a first light emitting diodes (LEDs), first alignment keys, and second alignment keys. The method comprises transferring the first LEDs and a portion of the second alignment keys included in the first wafer onto the donor substrate. The method comprises aligning a second wafer with the donor substrate, the second wafer including second LEDs, first alignment keys, second alignment keys, and third alignment keys of the second wafer. The second wafer is aligned with the donor substrate by aligning the portion of the second alignment keys of the first wafer that are disposed on the donor substrate with the third alignment keys of the second wafer.