Hybrid CMOS Micro-LED Power Layout for Uniform Current Injection
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Solution Overview
Problem
Existing CMOS power plane layouts for microLED displays face challenges in uniformly distributing current, leading to high current density and reliability issues due to non-uniform current distribution and excessive Ohmic losses, particularly in the μbumps, which can cause electromigration and heat-related failures.
Innovation Solution
A CMOS power plane layout with alternating Vled and Vcat contact areas and a large cathode redistribution ring surrounding the perimeter of the die area, allowing uniform current distribution along all four sides, reducing Ohmic losses, and using only one type of μbump for simplified manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the number of metal layers for power planes is minimized to reduce manufacturing cost, then manufacturing cost decreases, but current distribution uniformity deteriorates leading to current crowding effects
Solution Approach 1:
The power plane is segmented into multiple functional regions including cathode contact areas, Vled contact areas, and redistribution rings distributed across the substrate. This segmentation allows current to be distributed through multiple pathways rather than concentrated in single thick metal layers, achieving uniform current distribution while using fewer metal layers.
Solution Approach 2:
The patent transitions from vertical current distribution through stacked metal layers to horizontal current distribution across the substrate surface. By spreading current paths in the planar dimension rather than relying on vertical layering, the design achieves uniform current distribution with reduced metal layer count.
2Reliability
If current density in μbumps is reduced to prevent electromigration and heat losses, then reliability improves, but manufacturing complexity increases
Solution Approach 1:
The cathode contact structure is segmented into multiple contact points distributed around the pixel array perimeter, with each contact point connected to the LED cathode through individual μbumps. This segmentation distributes the total current across multiple lower-density pathways, reducing electromigration risk while maintaining a relatively simple manufacturing process.
3Reliability
If alternating Vled and Vcat contact areas are implemented to achieve uniform current distribution, then current distribution uniformity improves, but device complexity increases
Solution Approach 1:
The contact areas are segmented into alternating cathode contact regions and Vled contact regions arranged in a systematic pattern around the pixel array. This alternating segmentation creates balanced current distribution pathways while following a regular, repeatable layout pattern that simplifies manufacturing despite the increased structural complexity.
Solution Approach 2:
The cathode redistribution ring merges multiple cathode contact areas into a unified current distribution network that connects to the common cathode grid. This merging approach consolidates the alternating contact patterns into a cohesive structure that achieves uniform current distribution without requiring separate complex routing for each contact type.
Data Source
AI summary
Described is a CMOS power plane including interleaving contact areas, alternating Vled and Vcat contact areas, on at least two long sides of the μLED display area. By this way, Vled and cathode current are injected uniformly along the four sides of the μLED display panel. A large cathode current distribution ring on Vled and Vcat circuits is used to distribute the current along the four sides of the panel. The current distribution ring surrounds a pixel die area. An insulated area may be included on the cathode current redistribution ring adjacent one of the of μbumps.