Reverse-Tapered Deposition Mask for Shadow Defect Reduction
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Solution Overview
Problem
Wearable devices such as HMDs and AR glasses require high-resolution displays with pixel position accuracy (PPA) to prevent dizziness and discomfort, but existing deposition masks suffer from shadow defects and material buildup, affecting reliability.
Innovation Solution
A deposition mask with a reverse tapered shape formed by a second and third inorganic film pattern, using silicon oxide and silicon nitride, deposited via CVD or ALD methods, to improve PPA and reduce shadow defects and material buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional deposition mask is used for manufacturing high-resolution displays, then the display can be produced, but shadow defects and material buildup occur on the mask, affecting reliability
Solution Approach 1:
The mask membrane is designed with an asymmetric reverse tapered shape where the thickness varies across the surface. The third inorganic film is deposited to greater thickness at the side surface compared to the top surface, creating an asymmetric profile that prevents material buildup and shadow defects during deposition processes.
Solution Approach 2:
The reverse tapered shape is achieved by controlling the deposition parameters of the third inorganic film to create a specific thickness gradient. The thickness of the third inorganic film is precisely controlled to be greater at the side surface than at the top surface, forming the reverse tapered geometry that eliminates shadow defects.
2Manufacturing precision
If high-resolution display specifications are implemented, then pixel position accuracy is improved, but the complexity of the deposition mask increases
Solution Approach 1:
The mask membrane is segmented into multiple functional layers: a first inorganic film layer, a second inorganic film pattern layer, and a third inorganic film layer. This segmentation allows each layer to perform its specific function while collectively achieving the reverse tapered shape needed for high precision without excessive overall complexity.
Solution Approach 2:
The mask membrane uses composite inorganic film structures combining different materials (first inorganic film, second inorganic film, and third inorganic film). This composite structure enables precise control over the reverse tapered geometry and maintains manufacturing precision while managing structural complexity through material differentiation.
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
Enhances pixel position accuracy and reduces shadow defects and material buildup, improving the reliability of high-resolution displays in wearable devices.
Implementation Method 1
the third inorganic film may be deposited by using a chemical vapor deposition (CVD) method
Implementation Method 2
the third inorganic film may be deposited by using an atomic layer deposition (ALD) method
Data Source
AI summary
A deposition mask includes: a substrate; a first inorganic film on the substrate; and a mask membrane on the first inorganic film and including a second inorganic film and a third inorganic film. A cross-sectional structure of the mask membrane has a reverse tapered shape formed by a second inorganic film pattern obtained by patterning the second inorganic film and the third inorganic film covering a top surface and a side surface of the second inorganic film pattern.