Micro-LED Backside Groove Structure for Stronger Chip Bonding
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Solution Overview
Problem
The production yield of micro-LEDs is hindered by challenges in achieving sufficient bonding strength and effective luminous area due to limitations in chip size and metal electrode design, particularly in high-temperature fusion bonding processes.
Innovation Solution
A micro-LED design with a groove on its backside that exposes a first mesa and a second mesa, featuring metal electrodes within the groove and asymmetric electrode holes to enhance bonding, and a high-pressure bonding process using anisotropic conductive adhesive, optimizing chip structure and manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the chip size is reduced to increase pixel density, then the resolution is improved, but the bonding area of metal electrodes is reduced resulting in insufficient bonding strength
Solution Approach 1:
The patent introduces a vertical groove structure on the backside of the micro-LED chip, transforming the bonding area from a two-dimensional surface to a three-dimensional structure. The groove provides additional bonding area for the metal electrodes without increasing the chip's planar footprint, thus maintaining high pixel density while ensuring sufficient bonding strength.
Solution Approach 2:
The metal electrodes are nested within the groove structure, with the first metal electrode entirely disposed within the groove and the second metal electrode partially disposed within the groove. This nesting arrangement maximizes the use of available space and ensures adequate bonding area despite the small chip size.
2Strength
If the first metal electrode spans over to the second mesa to increase bonding area, then the bonding strength is improved, but the luminous area is reduced
Solution Approach 1:
Instead of expanding the metal electrode laterally onto the second mesa, the patent utilizes the vertical dimension by creating a groove and placing the metal electrodes within it. This preserves the full luminous area on the front surface while providing sufficient bonding area through the groove structure on the backside.
Solution Approach 2:
The bonding area is segmented into distinct regions: the first metal electrode is entirely within the groove, the second metal electrode is partially within the groove, and the groove sidewall is located between them. This segmentation prevents the first metal electrode from bridging onto the second mesa while ensuring adequate bonding area for both electrodes.
3Ease of manufacture
If a conventional high-temperature fusion bonding process is used, then the bonding process is simple, but the production yield is reduced due to insufficient bonding strength for micron-scale chiplets
Solution Approach 1:
The patent changes the bonding parameters from high-temperature fusion bonding to high-pressure bonding with anisotropic conductive adhesive. This parameter change enables reliable bonding of micron-scale chiplets while maintaining manufacturability, thus improving production yield without excessively complicating the manufacturing process.
Data Source
AI summary
A micro light-emitting diode (micro-LED) and a display apparatus are provided. The micro-LED includes a semiconductor layer sequence, which has a back side and a front side. The semiconductor layer sequence includes: a first-type semiconductor layer, a second-type semiconductor layer, and an active layer therebetween. The back side is provided with a groove, the groove penetrates through the second-type semiconductor layer and the active layer, and the first-type semiconductor layer is exposed through the groove. The back side includes: a first mesa, a second mesa, and a groove sidewall. A first metal electrode and a second metal electrode are disposed on the back side. The first metal electrode and the second metal electrode are configured for bonding with an external power supply. A backside surface of the second metal electrode defines a second electrode hole, which is located at a non-central position on the backside surface.