Display Panel Fabrication With Mixed TFTs and Low-Resistance Contacts
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Solution Overview
Problem
Existing display panel fabrication methods face challenges in achieving stable and reliable performance, particularly in flexible display panels with bending regions, due to issues with the integration and connectivity of thin-film transistors and capacitors.
Innovation Solution
A method is employed to form multiple thin-film transistors using different semiconductor materials, with a single mask for etching insulating layers to create contact holes and grooves, and a connection electrode with lower resistance is used to improve connectivity, along with a pixel definition layer to define light-emitting regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple thin-film transistors with different semiconductor materials are used in the pixel driving circuit, then the reliability and stability of the display panel is improved, but the manufacturing complexity and process difficulty increase
Solution Approach 1:
The pixel driving circuit is divided into multiple thin-film transistors (TFT1, TFT2, TFT3) with different semiconductor materials (oxide semiconductor, polysilicon, amorphous silicon) to perform specialized functions. Each TFT type is optimized for specific roles: oxide TFTs for low leakage current in switching operations, polysilicon TFTs for high mobility in driving operations, and amorphous silicon TFTs for cost-effective implementation. This segmentation allows each component to excel at its designated task, improving overall circuit reliability while maintaining manageable complexity through functional specialization.
Solution Approach 2:
Different semiconductor materials are strategically assigned to different TFT positions within the pixel circuit based on local functional requirements. Oxide semiconductors are used where low off-state current is critical (switching TFTs), polysilicon is used where high on-state current is needed (driving TFTs), and amorphous silicon is used in positions where cost and ease of fabrication are prioritized. This local optimization of material properties according to specific circuit node requirements enhances overall system reliability without requiring all components to use the same complex material system.
2Productivity
If a single mask is used for etching insulating layers to form contact holes and grooves, then the manufacturing efficiency is improved, but the etching precision and control difficulty increase
Solution Approach 1:
Multiple etching operations that would traditionally require separate masks are merged into a single etching process using one mask structure. The mask is designed with patterns that simultaneously define contact holes through first, second, and third insulating layers as well as grooves in the same insulating layer. This consolidation reduces the number of mask alignment steps, decreases manufacturing complexity, and improves production efficiency while maintaining acceptable etching precision through optimized single-step etching parameters.
Solution Approach 2:
The single mask structure serves multiple functions: it defines contact hole positions, contact hole dimensions, groove positions, and groove dimensions all in one patterning step. The mask pattern is designed to create various features (different sized contact holes, different shaped grooves) that serve different electrical and mechanical functions in the device. This multi-functional mask approach eliminates the need for multiple specialized masks, streamlining the fabrication process while achieving the required precision for each feature type through careful mask design and single-step etching optimization.
3Reliability
If a connection electrode with lower resistance material is used, then the electrical connectivity is improved, but the material selection and manufacturing complexity increase
Solution Approach 1:
The connection electrode material is selected to have significantly lower electrical resistance compared to conventional electrode materials. By changing the material parameter (resistance) of the connection electrode, the electrical connectivity between the pixel driving circuit and the display device is substantially improved. This parameter change addresses the critical need for low-resistance connections in high-performance display panels, ensuring stable signal transmission and reducing voltage drops across connection points.
Solution Approach 2:
The connection electrode is formed using a composite material structure or a specialized low-resistance material that combines the desirable properties of low electrical resistance with compatibility to existing fabrication processes. The material selection balances the need for low resistance with considerations for adhesion to underlying layers, etch selectivity, and compatibility with subsequent processing steps. This approach improves electrical connectivity while managing manufacturing complexity by selecting materials that can be integrated into the existing thin-film deposition and patterning toolset.
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
This approach enhances the stability and reliability of display panels by improving the electrical characteristics and reducing contact resistance, leading to more efficient and durable pixel driving circuits.
Implementation Method 1
the organic layer may be formed to fill the first groove and the second groove
Implementation Method 2
the etching of the first, second, and third insulating layers may be performed to simultaneously form the first and second contact holes and the first groove
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A method of fabricating a display panel may include forming an oxide semiconductor pattern on a base layer including a first region and a second region, etching first, second, and third insulating layers to form a first groove that overlaps the second region, forming electrodes on the third insulating layer, forming a fourth insulating layer on the third insulating layer to cover the electrodes, thermally treating the fourth insulating layer, forming an organic layer to cover the fourth insulating layer, and forming an organic light emitting diode on the organic layer.