OLED Display Planarization With Pad Electrode Sidewall Capping
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in improving display quality due to thickness differences caused by complex stacked structures under the planarization layer, which affect optical characteristics and light efficiency.
Innovation Solution
A method involving a CMP process using a sacrificial layer with different etch selectivity to polish the planarization layer, resulting in a capping layer that protects the pad electrode and line from corrosion by capping their side surfaces, and forming an organic light emitting diode with specific electrode structures to enhance display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a planarization layer is formed to cover complex stacked structures, then the surface is planarized, but thickness differences remain that affect optical characteristics and light efficiency
Solution Approach 1:
The planarization layer is divided into two regions: a first region in the display area with a first thickness, and a second region in the non-display area with a second thickness greater than the first thickness. This segmentation allows the display area to achieve proper planarity for optical performance while the non-display area provides additional height for capping structures.
2Area of stationary object
If the planarization layer is made thicker to cover underlying structures, then coverage is improved, but optical characteristics and light efficiency deteriorate due to excessive thickness
Solution Approach 1:
Different thicknesses are applied to different regions: the first region (display area) has a controlled first thickness optimized for light efficiency and optical characteristics, while the second region (non-display area) has a greater second thickness to provide capping functionality. This local differentiation ensures optimal performance in the display area while maintaining structural coverage.
3Ease of manufacture
If the pad electrode side surfaces are exposed, then manufacturing is simplified, but the pad electrode and line are susceptible to corrosion and damage
Solution Approach 1:
The planarization layer is formed with extended thickness in the non-display area before the pad electrode and line are fully processed. This preliminary action creates a built-in capping structure that protects the pad electrode side surfaces and line from corrosion and damage throughout subsequent manufacturing steps and device operation.
4Reliability
If a capping layer is added to protect the pad electrode, then reliability is improved, but device complexity increases
Solution Approach 1:
The planarization layer serves multiple functions: it provides surface planarity for the display area, acts as an insulating layer, and simultaneously functions as a capping layer for the pad electrode and line in the non-display area by having extended thickness in that region. This multi-functionality eliminates the need for a separate dedicated capping layer, reducing overall device complexity.
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 method improves optical characteristics and light efficiency by planarizing the display area and protects the pad electrode and line from damage, thereby enhancing the overall display quality of the organic light emitting display device.
Implementation Method 1
polishing the planarization layer and the sacrificial layer by a chemical mechanical polishing (CMP) process
Implementation Method 2
The sacrificial layer may include a material having an etch selectivity in the chemical mechanical polishing process that is different from an etch selectivity of the planarization layer
Data Source
AI summary
A display device includes a planarization layer covering transistors in a display area on a substrate, an organic light emitting diode on the planarization layer, a pad electrode in a non-display area on the substrate surrounding the display area, and a sacrificial layer remnant capping a side surface of the pad electrode.