LED Display Planarization Structure for Misalignment-Tolerant Contacts
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Solution Overview
Problem
Display devices using light emitting diodes (LEDs) face issues with electrode contact failures and residual film formation due to misalignment during the transfer process, leading to short circuits and reduced contact area effectiveness.
Innovation Solution
A display device design incorporating a dual planarization layer structure, where a first planarization layer with a stepped thickness encloses the LED and a second planarization layer ensures stable electrode contact, formed using a halftone mask photolithographic process to minimize residual film and enhance contact area reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single planarization layer is used to enclose the light emitting diode, then the structure is simple and manufacturing is easier, but the electrode contact area is reduced and contact reliability deteriorates when transfer misalignment occurs
Solution Approach 1:
The planarization layer is divided into multiple separate layers (first planarization layer and second planarization layer) instead of using a single layer. The first planarization layer encloses the lower portion of the LED, while the second planarization layer encloses the upper portion, creating a stepped structure that maintains contact area despite transfer misalignment.
Solution Approach 2:
The solution transitions from a single-layer planar structure to a multi-layer stepped structure in the vertical dimension. The first planarization layer has a first thickness and the second planarization layer has a second thickness greater than the first, creating a stepped profile that compensates for horizontal misalignment during transfer.
2Loss of substance
If the planarization layer thickness is reduced to minimize residual film formation, then residual film is reduced, but the contact hole area and electrode contact stability are compromised
Solution Approach 1:
The planarization function is segmented into two layers with different thicknesses. The first planarization layer can be made thinner to reduce residual film, while the second planarization layer provides additional thickness to ensure adequate contact hole area and alignment tolerance, resolving the contradiction between minimizing residual film and maintaining contact precision.
Solution Approach 2:
Different regions of the planarization structure have different thicknesses optimized for different functions. The first planarization layer region has a first thickness optimized for minimizing residual film, while the second planarization layer region has a second thickness optimized for ensuring contact hole stability and alignment tolerance.
3Reliability
If the light emitting diode is transferred with precise alignment, then electrode contact is maximized, but the transfer process complexity and alignment requirements increase
Solution Approach 1:
The multi-layer stepped planarization structure is prepared in advance to compensate for potential transfer misalignment. The stepped configuration with different thicknesses creates a tolerance buffer that maintains adequate contact area even when the LED transfer position is dislocated, reducing the stringency of alignment requirements.
Solution Approach 2:
The planarization structure uses varying thickness parameters (first thickness and second thickness where the second is greater than the first) to create a stepped profile that is more tolerant to position variations during transfer, thereby reducing transfer process complexity while maintaining contact reliability.
4Manufacturing precision
If a thick planarization layer is used to ensure contact hole area, then contact stability is improved, but residual film generation increases and manufacturing complexity increases
Solution Approach 1:
The planarization function is divided into two layers where the first layer can be made thinner to reduce residual film, while the cumulative thickness of both layers ensures adequate contact hole area. This segmentation allows optimization of each layer's thickness for its specific function.
Solution Approach 2:
The solution moves from a single thick layer to a multi-layer stepped structure in the vertical dimension. The first planarization layer has a first thickness and the second planarization layer has a second thickness greater than the first, creating a stepped profile that provides adequate contact area while allowing the individual layers to be optimized for reduced residual film.
Data Source
AI summary
A display device is disclosed. The display device comprises a display panel including a plurality of subpixels; a light emitting diode in a subpixel from the plurality of sub pixels; a first planarization layer that encloses the light emitting diode; a second planarization layer on the first planarization layer and the light emitting diode; and a connection electrode on the second planarization layer and connected to the light emitting diode. The first planarization layer includes a first open area that encloses the light emitting diode and a portion of the first planarization layer corresponding to the first open area has a first thickness that is less than a second thickness of a second portion of the first planarization layer.