Passivated Stacked Micro LED Chip for Bright, Damage-Resistant Pixels
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Solution Overview
Problem
Micro LEDs are difficult to handle and mount on display panels due to their small form factor, prone to damage from external shocks, and require significant area for sub-pixels, which can reduce brightness and necessitate color filters between stacked sub-units.
Innovation Solution
A light emitting chip with a vertically stacked structure of sub-units, covered by a passivation layer, allows for increased luminous area without increasing pixel size, enabling independent driving and omitting color filters between sub-units, and includes a conductive pattern for electrical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If micro LEDs are used with small form factor, then pixel area is reduced, but handling difficulty and susceptibility to damage increase
Solution Approach 1:
A passivation layer is formed to cover the light emitting structure before mounting, providing protective cushioning against external shocks and handling damage. This pre-protection mechanism allows micro LEDs to maintain small form factor while improving reliability during transportation and mounting processes.
2Productivity
If sub pixel area is reduced to fit more pixels, then pixel density is increased, but brightness deteriorates
Solution Approach 1:
By stacking multiple light emitting sub-units vertically, the luminous area is increased in the vertical dimension while maintaining a compact horizontal footprint. This allows higher pixel density without reducing the effective发光 area of each sub-pixel, thereby maintaining brightness while increasing pixel density.
Solution Approach 2:
Multiple light emitting sub-units are combined in a vertical stack within a single pixel structure. The combined luminous output of stacked sub-units provides sufficient brightness while occupying a smaller horizontal area, enabling higher pixel density without sacrificing illumination intensity.
3Manufacturing precision
If color filters are used between stacked sub-units, then color accuracy is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the color filter layer from the traditional micro LED structure. Instead of using color filters to achieve full-color display, the invention uses directly stacked red, green, and blue light emitting sub-units. This extraction simplifies the device structure by eliminating the color filter component and associated alignment requirements.
Solution Approach 2:
The patent uses direct emission from multiple quantum well structures with different bandgaps to produce red, green, and blue light, replacing the need for color filters. Each quantum well structure is engineered to emit a specific wavelength, creating a direct optical copy of the desired color without requiring filtering.
Data Source
AI summary
A light emitting chip including a light emitting structure including first, second, and third light emitting sub-units to emit light of a first color, a second color, and a third color and vertically stacked on each other, and having at least one mesa structure and at least one sidewall having a stepped structure; a plurality of vias electrically connected to the light emitting sub-units, each via has a top surface exposed from the light emitting structure and a bottom surface contacting the light emitting structure, a part of the bottom surfaces of the vias disposed on substantially the same level; and a first passivation layer covering at least a part of the light emitting structure, in which the first passivation layer has a bottom surface exposing the light emitting structure to permit light from the first, second, and third sub-units to be emitted from the light emitting chip.