Deposition Mask Pixel Openings for Uniform OLED Layer Thickness
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Solution Overview
Problem
In the manufacturing of high-resolution display panels for wearable devices like HMDs and AR glasses, the uneven thickness and size of organic light-emitting layers result from pixel openings with a lower width smaller than the upper width, leading to deposition material loss and non-uniform layer formation.
Innovation Solution
A deposition mask with pixel openings designed to have a larger lower width than upper width, featuring a silicon layer and an inorganic layer with specific stress properties, and a method of manufacturing this mask through controlled etching processes to ensure uniform layer deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pixel openings are formed with lower width smaller than upper width through anisotropic etching, then manufacturing process is simplified, but deposition material loss increases and layer uniformity deteriorates
Solution Approach 1:
The patent applies asymmetry by designing the pixel opening with different widths at the lower and upper portions. Specifically, the lower width (at the backplane substrate) is made larger than the upper width (at the membrane), creating a tapered shape that compensates for deposition material loss during the deposition process. This asymmetric geometry ensures uniform organic light-emitting layer thickness despite the simplified anisotropic etching process.
Solution Approach 2:
The patent changes the geometric parameters of the pixel opening by controlling the etching depth and angle to achieve specific width ratios between the lower and upper portions. The lower width is designed to be 1.05 to 1.2 times the upper width, optimizing the balance between material loss compensation and manufacturing simplicity.
2Ease of manufacture
If pixel openings have smaller lower width, then anisotropic etching is easier to implement, but organic light-emitting layer thickness uniformity deteriorates
Solution Approach 1:
The patent inverts the conventional approach by making the lower width larger than the upper width, opposite to the typical tapered structure. This inversion compensates for the natural tendency of deposition material to accumulate less at narrower regions, ensuring uniform layer thickness across the pixel opening despite the simplified etching process.
3Device complexity
If conventional deposition mask structure is used, then manufacturing process is simpler, but display quality and layer uniformity deteriorate
Solution Approach 1:
The patent applies local quality by creating different width characteristics at different locations of the pixel opening. The lower portion has a larger width to prevent material loss, while the upper portion maintains a smaller width for precise pattern definition. This localized geometric variation ensures uniform deposition quality without requiring complex overall mask structures.
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
The solution reduces material loss and achieves uniform thickness and size of light-emitting layers, enhancing the display quality and durability of high-resolution wearable devices.
Implementation Method 1
The inorganic layer may include silicon nitride having residual tensile stress... the insulating layer may include silicon oxide having residual compressive stress
Data Source
AI summary
A deposition mask includes a mask frame defining a cell opening, and a membrane including a silicon layer disposed on the mask frame and an inorganic layer disposed on the silicon layer. The membrane includes a cell region disposed above the cell opening, and the cell region has a plurality of pixel openings. Each of the pixel openings includes a first opening penetrating the inorganic layer and a second opening penetrating the silicon layer, and the second opening has a larger width than a width of the first opening.