Micro-LED Contact Deposition to Cut Sidewall Light Loss
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Solution Overview
Problem
Current methods for producing micro-LEDs lack an efficient and simple way to form electric contacts and reduce light loss through sidewalls, which affects the performance and efficiency of micro-LED displays.
Innovation Solution
A micro-LED structure with a conductive layer that protrudes into a through-opening in the insulating layer, allowing electrical contact with the doped layers and acting as a mirror to minimize light loss, is formed using a material beam deposition process, where the array of micro-LEDs is inclined to prevent exposure of the conductive layer to the substrate and ensure proper contact without shortcuts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a lithographic process is used to form electric contacts on the first insulating layer, then the manufacturing precision can be improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces the lithographic process (which involves photoresist coating, patterning, and etching) with a direct deposition method where the conductive layer is deposited directly onto the first insulating layer to form electric contacts. This substitution eliminates the complex lithographic steps while achieving the required contact formation precision through controlled deposition processes.
Solution Approach 2:
The patent extracts and removes the lithographic process steps from the manufacturing sequence, directly forming the conductive layer on the insulating layer without intermediate lithographic patterning. This extraction simplifies the overall manufacturing process while maintaining the necessary precision for electric contact formation.
2Loss of energy
If the conductive layer completely covers the second insulating layer on the sidewalls, then the light loss through sidewalls is reduced, but the risk of creating electrical shortcuts to the substrate increases
Solution Approach 1:
The patent applies different coverage characteristics of the conductive layer to different regions: on the upper surface, the conductive layer forms complete electric contacts through through-openings in the first insulating layer, while on the sidewalls, it partially covers the second insulating layer to reduce light loss without reaching the substrate. This local differentiation of coverage quality optimizes both light extraction and electrical isolation.
Solution Approach 2:
The conductive layer is applied in a partial manner on the sidewalls - enough to cover the upper portion for light reflection but not excessive enough to reach the substrate and create shortcuts. This partial action achieves the beneficial light management effect while avoiding the harmful electrical conduction effect.
3Reliability
If the array of micro-LEDs is inclined during material beam deposition, then the conductive layer coverage on sidewalls is controlled to prevent shortcuts, but the manufacturing complexity increases
Solution Approach 1:
The patent introduces dynamic positioning of the micro-LED array during deposition - the array is inclined at a specific angle relative to the material beam direction. This dynamic adjustment of the substrate orientation during the deposition process enables precise control of conductive layer coverage on sidewalls, preventing shortcuts while maintaining manufacturing feasibility through controlled motion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables effective electrical contact and reduces light loss through the sidewalls, improving the efficiency and performance of micro-LED displays by using a lithography-free process that ensures proper contact and minimizes non-radiative losses.
Implementation Method 1
The conductive layer can be formed in a simple way, in particular in comparison to a lithographic process that might also be used to form an electric contact on the first insulating layer
Implementation Method 2
The conductive layer on the sidewalls can therefore cause a reduction in the loss of light through the sidewalls
Data Source
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AI summary
A method of producing an array of micro-LEDs (11), the method comprises the step of: providing an array of micro-LEDs (11)comprising: a substrate (13), and a plurality of micro-LEDs (15), wherein the micro-LEDs (15) form an array-like arrangement on a topside (17) of the substrate (13), and wherein a lower surface (27) of each micro-LED (15) is arranged on the topside (17) of the substrate (13), wherein each micro-LED (15) comprises: a layered structure with a first doped layer (19), a second doped layer (21), and an active layer (23) between the first doped layer (19) and the second doped layer (21), wherein the layered structure has sidewalls (25) extending between an upper surface (27) and a lower surface (29) of the layered structure and forming an outer boundary of at least the first doped layer (19), the second doped layer (21), and the active layer (23), wherein the upper surface (27) extends above the first doped layer (19) and the lower surface (29) extends below the second doped layer (21), wherein a first insulating layer (31) is arranged on the upper surface (27) and a second insulating layer (33) is arranged on the sidewalls (25), wherein the first insulating layer (31) has a through opening (35) at the upper surface (27), the method further comprises the step of: depositing a conductive layer (37) on each of the micro-LEDs (15) of the array of micro-LEDs (11), such that the conductive layer (37) is disposed over the first insulating layer (31) and protrudes into the opening (35) and contacts the upper surface (27) and such that the conductive layer (37) covers the second insulating layer (33), wherein the step of depositing the conductive layer (37) comprises: exposing the array of micro-LEDs to a material beam (41) comprising material for forming the conductive layer (37), wherein the material beam (15) has a beam direction (D), and wherein the array of micro-LEDs (11) is disposed in the material beam (41) such that the micro-LEDs (15) face the material beam (41), wherein a surface normal (N) is perpendicular to the topside (17) of the substrate (13), and wherein the surface normal (N) and the beam direction (D) include an angle (α) which is not zero degrees.