Stepped Contact Hole Structure for LED Display Pixel Electrodes
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Solution Overview
Problem
Display devices face challenges with pixel electrode disconnection and exposure of light emitting diode side surfaces through contact holes, which affect manufacturing costs and display quality.
Innovation Solution
A display device design featuring a substrate with sub-pixels and a planarization layer that includes a first contact hole with a step shape, minimizing pixel electrode disconnection and allowing for various contact hole forms, thereby reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional contact hole design is used, then the manufacturing process is simple, but pixel electrode disconnection occurs and light emitting diode side surfaces are exposed
Solution Approach 1:
The contact hole is divided into multiple sections with different widths along the depth direction. The upper portion has a first width, the lower portion has a second width smaller than the first, creating a stepped structure. This segmentation allows the contact hole to simultaneously provide adequate support area at the top while minimizing exposure at the bottom, thus preventing pixel electrode disconnection without excessive complexity.
Solution Approach 2:
Different portions of the contact hole are given different dimensional characteristics. The upper portion maintains a larger width to ensure proper alignment and reduce disconnection risk, while the lower portion is narrowed to minimize light emitting diode side surface exposure. This local differentiation of quality optimizes both reliability and performance.
2Object-affected harmful factors
If the contact hole width is reduced to minimize LED exposure, then display quality improves, but pixel electrode disconnection risk increases
Solution Approach 1:
The contact hole width is segmented into two distinct zones: an upper zone with larger width that ensures adequate pixel electrode contact area for reliable connection, and a lower zone with smaller width that minimizes LED side surface exposure. This segmentation resolves the contradiction by providing both widths in different spatial locations within the same contact hole structure.
Solution Approach 2:
The solution moves from considering only the cross-sectional width of the contact hole to a three-dimensional stepped structure with varying width along the depth dimension. By utilizing the depth dimension, the design achieves both large width (for reliability) at the upper portion and small width (for minimal exposure) at the lower portion, resolving the contradiction through dimensional transition.
3Adaptability or versatility
If various contact hole shapes are designed, then display quality and manufacturing flexibility improve, but manufacturing cost increases
Solution Approach 1:
The stepped contact hole structure serves multiple functions: it provides adequate alignment margin for pixel electrode placement, minimizes LED side surface exposure, and maintains compatibility with existing manufacturing processes. This universal design achieves design flexibility without increasing manufacturing cost by using a structure that can be implemented with standard fabrication techniques.
Data Source
AI summary
According to an aspect of the present disclosure, a display device includes a substrate in which a plurality of sub pixels is defined; a light emitting diode disposed on the substrate in each of the plurality of sub pixels; and a planarization layer which covers the light emitting diode and includes a first contact hole overlapping the light emitting diode. The first contact hole is formed to have a width which is narrowed from an upper portion of the first contact hole toward a lower portion of the first contact hole. Accordingly, the first contact hole is formed to have a step shape so that the exposure of the side surface part of the light emitting diode through the first contact hole and the disconnection of the pixel electrode may be minimized.