Micro-LED Chip Transfer Mask Layout to Minimize Wafer Scrap
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Solution Overview
Problem
The efficiency of using micro-LED chips on a wafer is lowered due to the laser lift-off (LLO) transfer method, which results in scrap blocks on the wafer not being used for transfer.
Innovation Solution
A micro-LED chip transfer method based on laser lift-off (LLO) that involves determining a block-specific LED chip map to identify unused LED chips, calculating a mask size to minimize scrap blocks, and positioning the mask to optimize the transfer of LED chips onto a glass substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser lift-off transfer is performed on entire wafer blocks, then transfer process is simplified, but micro-LED chip usage efficiency deteriorates due to scrap blocks
Solution Approach 1:
The wafer is divided into multiple blocks, and the transfer process is segmented to handle only the necessary blocks containing usable micro-LED chips. The controller identifies and selects specific blocks for transfer based on chip availability, avoiding unnecessary transfer of entire wafer areas and eliminating scrap blocks.
Solution Approach 2:
The system performs preliminary identification of usable micro-LED chips and their block locations before the transfer process. The controller pre-determines which blocks contain transferable chips and plans the transfer sequence accordingly, ensuring optimal utilization of available chips while avoiding scrap generation.
2Ease of manufacture
If transfer is performed in integer multiples of blocks, then processing is standardized, but edge blocks may be wasted reducing efficiency
Solution Approach 1:
The transfer process is made dynamic by allowing flexible selection of block combinations based on actual chip availability. The controller can transfer varying numbers of blocks (e.g., 1-6 blocks) depending on which blocks contain usable chips, rather than being constrained to fixed integer multiples. This dynamic approach ensures edge blocks are utilized when containing valid chips.
Solution Approach 2:
Different blocks are treated differently based on their specific content and position. The controller evaluates each block individually to determine whether it contains transferable chips, allowing edge blocks to be included in transfer when they contain usable chips, rather than applying a uniform transfer rule to all blocks.
3Productivity
If all blocks on wafer are transferred, then maximum chips are utilized, but transfer time increases due to unnecessary transfers
Solution Approach 1:
The system extracts and transfers only the necessary blocks containing usable micro-LED chips, leaving blocks with defective or unusable chips on the wafer. The controller identifies and isolates transferable blocks from non-transferable ones, performing transfer operations only on the extracted subset of blocks, thereby reducing total transfer time while maintaining high chip utilization.
Solution Approach 2:
The transfer process skips blocks that do not contain transferable chips, moving directly from one transferable block to the next. The controller identifies contiguous transferable blocks and performs rapid sequential transfer operations, eliminating delays associated with processing non-transferable blocks and reducing overall transfer time.
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 efficiency of using micro-LED chips by minimizing scrap blocks and optimizing the transfer process, thereby improving the utilization of micro-LED chips on the wafer.
Implementation Method 1
absorption of the laser beam occurs in the release layer, and thus the release layer is decomposed. That is, as a laser beam of a specific wavelength is absorbed in the release layer, and the release layer is heated accordingly, thermal decomposition occurs.
Implementation Method 2
absorption of the laser beam occurs in the release layer, and thus the release layer is decomposed
Implementation Method 3
lift-off occurs and lifts a device when volatile atoms, e.g., N2, O2, and H2, are generated between the release layer and the device by thermal decomposition
Data Source
AI summary
A micro LED chip transfer method includes: determining the transfer object size for a transfer, by using a block-by-block LED chip map in which the use state information of an LED chip is stored for each block of the wafer; determining a mask size that can minimize a scrap block of the wafer that is not used for transfer, by using the transfer object size; determining a starting point position of the wafer transfer object region for transfer; and positioning a mask having the mask size at the starting point position of the wafer transfer object region and irradiating a laser, such that the LED chip formed in the wafer transfer object region is transferred.