Collimating Shadow Mask for OLED Micro-Display Patterning
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Solution Overview
Problem
Current technologies for manufacturing high resolution OLED micro-displays face issues with light emission efficiency due to the use of color filters, which absorb 80% of light, and existing patterning methods like LITI and contact metal shadow masks struggle with resolution and accuracy for small sub-pixels, leading to blurring and stoichiometry changes.
Innovation Solution
A high precision, high resolution collimating shadow mask made of materials like Si, Si3N4, and SiO2 is developed, which allows for precise patterning of OLED sub-pixels without contacting the substrate, reducing feathering and image shift, and maintaining material stoichiometry, by creating a silicon substrate with reduced thickness and aligned openings for precise organic material deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If color filters are used to create full color OLED micro-displays, then color display capability is achieved, but light emission efficiency deteriorates due to 80% light absorption
Solution Approach 1:
The patent removes color filters from the display structure and instead uses a shadow mask with precisely positioned openings to define sub-pixel patterns. This extraction of the color filtering function eliminates the 80% light absorption problem while maintaining full color capability through direct OLED material patterning in red, green, and blue regions.
Solution Approach 2:
Instead of using a white OLED emitter with color filters to achieve full color, the patent inverts the approach by directly patterning the OLED emissive layer with different organic materials in red, green, and blue regions. This eliminates the need for light absorption-based color filtering and enables efficient light emission across all color channels.
2Manufacturing precision
If LITI method is used for patterning OLED materials, then large area displays can be manufactured, but resolution and positioning accuracy deteriorate for small sub-pixels due to beam blurring
Solution Approach 1:
The patent introduces a shadow mask as an intermediary component between the deposition source and the substrate. This mask with precisely positioned openings defines the sub-pixel patterns, eliminating beam blurring and feathering issues that occur with direct LITI methods. The mask acts as a physical template that ensures sharp edges and accurate positioning.
Solution Approach 2:
The patent replaces the mechanical beam scanning and focusing system of LITI with a static shadow mask structure. Instead of relying on precise beam control and focusing mechanics, the pattern definition is achieved through the fixed geometric structure of the mask openings, which inherently provides sharp edges and consistent positioning.
3Ease of manufacture
If contact metal shadow mask is used for patterning, then manufacturing process is simplified, but resolution deteriorates for sub-pixels smaller than 10 by 10 microns
Solution Approach 1:
The patent uses a thin film shadow mask structure that can be fabricated with high precision openings using standard semiconductor manufacturing techniques. This thin film approach allows for sub-10-micron resolution while maintaining ease of manufacture through established processes like lithography and etching, overcoming the resolution limitations of contact metal masks.
Solution Approach 2:
The patent changes the key parameter of mask-substrate distance from zero (contact) to a small gap distance. This parameter change enables high resolution patterning of sub-10-micron sub-pixels by allowing precise beam control through the mask openings while preventing the resolution degradation that occurs with contact masks due to material diffusion and stoichiometry changes.
4Manufacturing precision
If mask thickness is increased to reduce feathering, then sub-pixel edge sharpness is improved, but mask complexity and fabrication difficulty increase
Solution Approach 1:
The patent employs a thin film shadow mask that achieves sharp sub-pixel edges through precise opening geometry and optimal gap distance control rather than increased thickness. This thin film approach reduces mask complexity and fabrication difficulty while maintaining edge sharpness, as the thin structure is more easily fabricated with standard semiconductor processes and allows better beam control.
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 approach enables the fabrication of high resolution, full color OLED micro-displays with improved light emission efficiency, maintaining display performance and achieving high dimensional and positional accuracy without the need for perfect substrate flatness or uniform gap distances.
Implementation Method 1
The mask is exposed to a beam from a linear evaporation source and organic materials are deposited to form the sub-pixel
Data Source
AI summary
The method for producing an OLED micro-display on a silicon wafer uses a collimating shadow mask formed on a silicon substrate. The mask is fabricated by depositing a material layer on the front side and on the back side of the substrate and etching a portion of the layer on the back side of the substrate to a reduced thickness of at least 20 microns. At least one opening is created in the etched portion of the substrate. The substrate beneath the opening is removed to create the mask. The mask is situated at a location spaced from the surface of the silicon wafer and exposed to a linear evaporation source. Organic layers are then deposited on the silicon wafer in a location aligned with the mask opening.