Epitaxial Alignment Structure for Precise Micro LED Transfer
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Solution Overview
Problem
Current micro LED transfer methods face challenges with inaccurate chip alignment and misplacement due to the large contact area of transfer heads, leading to low pick-up yield and potential chip damage during bonding.
Innovation Solution
The introduction of a semiconductor pickup element with guiding structures and alignment structures on the epitaxial structure, allowing for precise alignment and pick-up of the epitaxial structure, preventing shift and ensuring accurate positioning during transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the contact area of the transfer head is designed to be much larger than that of the chip to avoid low pick-up yield, then the pick-up yield is improved, but the alignment precision deteriorates causing the chip to be misaligned with the calibration bump pad
Solution Approach 1:
The transfer head contact area is divided into multiple discrete contact points rather than a continuous large contact surface. This segmentation allows the transfer head to maintain sufficient contact area for reliable pick-up while enabling precise positioning through individual point contacts, thereby resolving the contradiction between pick-up yield and alignment precision
Solution Approach 2:
Different regions of the transfer head are designed with different properties - the contact points have localized adhesive properties while the overall structure maintains precise positioning capabilities. This local differentiation allows the system to achieve both high pick-up yield through adequate contact area and high alignment precision through controlled contact geometry
2Strength
If the contact position is difficult to accurately control and the entire contact surface is glued to provide adhesion, then the adhesion is improved, but the positioning accuracy deteriorates causing shift during bonding
Solution Approach 1:
The continuous glued contact surface is segmented into discrete contact points or zones. This segmentation maintains sufficient adhesion strength through concentrated contact areas while enabling precise positioning control, as the segmented structure allows for better tolerance to positioning variations and reduces the risk of shift during bonding operations
3Productivity
If a single transfer head picks up multiple chips in a dense chip array, then the productivity is improved, but the alignment precision deteriorates making it difficult to place each chip accurately
Solution Approach 1:
The transfer head is designed with multiple independently controllable contact points or segments, each capable of picking up and positioning individual chips. This segmentation enables the transfer head to handle multiple chips simultaneously while maintaining precise control over each chip's placement position, thereby resolving the contradiction between transfer efficiency and placement precision
Solution Approach 2:
The transfer head incorporates dynamic control capabilities that allow independent adjustment of each contact point's position and adhesive properties. This dynamic control enables the system to adapt to different chip positions in the dense array while maintaining high placement precision for each chip, thus achieving both high productivity and high precision
4Reliability
If the chip picked up is bigger than the area of the corresponding bump pad, then the pick-up robustness is improved, but the bonding quality deteriorates due to uneven force crushing the chip
Solution Approach 1:
The contact interface between the transfer head and chip is designed with localized contact points that concentrate the picking-up force on specific regions of the chip. This local quality approach ensures robust pick-up of larger chips while distributing the bonding force evenly during the bonding process, preventing chip crushing and maintaining high bonding quality
Data Source
AI summary
An epitaxial structure adapted to a semiconductor pickup element is provided. The semiconductor pickup element has at least one guiding structure and provided with a pickup portion. The epitaxial structure includes a semiconductor layer corresponding to the pickup portion and capable of being picked up by the semiconductor pickup element. The epitaxial structure also includes at least one alignment structure disposed on the semiconductor layer and corresponding to the at least one guiding structure, so that the epitaxial structure and the semiconductor pickup element are positioned relative to each other. The number of the at least one alignment structure matches the number of the at least one guiding structure.