Deposition Mask with Reverse Tapered Grids for Shadow Defect Reduction
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Solution Overview
Problem
Existing deposition masks for high-resolution organic light emitting display devices face challenges in achieving improved pixel position accuracy, reducing shadow defects, and preventing the accumulation of deposition material on the mask.
Innovation Solution
A deposition mask with a silicon substrate and mask grids that have a reverse tapered shape with a width increasing from the back surface to the upper surface, and side surfaces with concave curved surfaces to reduce shadow defects and material accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional deposition masks are used, then manufacturing process is simple, but pixel position accuracy is insufficient
Solution Approach 1:
The mask structure is segmented into multiple functional components: mask grids with specific geometries, concave curved surfaces, and reverse tapered shapes. Each segment serves a specific function in achieving pixel position accuracy while managing complexity through modular design
Solution Approach 2:
Different regions of the mask are given different local properties: the mask grids have reverse tapered shapes with specific angle ranges (65-88 degrees), side surfaces have concave curved surfaces with controlled depths (up to 20% of mask thickness), and materials are selected from specific groups (Si, SiNx, SiON, SiOx, TiOx, a-Si, AlOx for inorganic layers; Cu, Ni, Al, W, Mo, Ti, Invar for metal layers) to optimize local deposition characteristics
2Object-affected harmful factors
If conventional mask geometry is used, then manufacturing is easier, but shadow defects occur
Solution Approach 1:
The mask grids are designed with curved surfaces instead of flat surfaces. The side surfaces include concave curved surfaces that redirect deposited material away from shadow regions, eliminating shadow defects caused by planar geometries while maintaining manufacturability through controlled curvature depths
Solution Approach 2:
Instead of having convex outward surfaces that cast shadows, the mask grids are inverted to have concave surfaces that catch and redirect material flow, preventing shadow defect formation in the underlying substrate regions
3Duration of action of stationary object
If conventional mask structure is used, then initial cost is lower, but material accumulation reduces number of uses
Solution Approach 1:
The concave curved surfaces on the mask grids prevent material accumulation by creating surfaces where deposited material does not adhere strongly. The curved geometry allows material to be shed more easily, extending the operational life of the mask before replacement is needed
Solution Approach 2:
The reverse tapered shape with wider upper surface than back surface converts the potential harm of material accumulation into a benefit: the geometry allows controlled material buildup on the upper surface that does not affect the critical lower surface, and can even be used to monitor deposition rates while maintaining mask functionality
Data Source
AI summary
A deposition mask includes a mask body including a silicon substrate, where a plurality of holes is defined through the mask body, and the mask body further includes mask grids extending to define the holes. A cross section of each mask grid has a reverse tapered shape having a width increasing from a back surface to an upper surface of the deposition mask, and each side surface of each mask grid defining a hole includes a first concave curved surface.