OLED Drive Transistor Layout to Prevent Bright Spot Leakage
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Solution Overview
Problem
In organic electroluminescence display devices, unreacted metal can diffuse into the silicon substrate during silicide formation, leading to unnecessary leakage currents and bright spot defects due to unwanted light emission.
Innovation Solution
A display device configuration where a transistor in the drive circuit includes a diffusion layer without silicide, preventing unreacted metal from diffusing and forming a first contact electrode, while another diffusion layer with silicide is used for reduced contact resistance, with an insulating film covering the silicide-free region to prevent metal diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicide is formed in the diffusion layer to reduce contact resistance, then contact resistance is reduced, but unreacted metal diffuses into the silicon substrate causing leakage current and bright spot defects
Solution Approach 1:
The diffusion layers are segmented into two types: first diffusion layers without silicide for connecting to light-emitting portions, and second diffusion layers with silicide for other connections. This segmentation allows selective application of silicide formation based on functional requirements, preventing metal diffusion to light-emitting portions while maintaining low contact resistance where needed.
Solution Approach 2:
Different regions of the substrate are given different properties: regions connected to light-emitting portions have no silicide (first diffusion layers) to prevent metal diffusion, while other regions have silicide formed (second diffusion layers) to reduce contact resistance. This local differentiation resolves the contradiction by applying the harmful factor (silicide) only where beneficial.
2Reliability
If metal layer is formed on diffusion layer for silicide formation, then contact resistance is reduced, but unreacted metal becomes leakage source
Solution Approach 1:
The metal layer formation process is segmented: metal layers are formed only on second diffusion layers where silicide is desired, while first diffusion layers are excluded from metal layer formation. This prevents unreacted metal from appearing on light-emitting portion connections while maintaining low contact resistance on other connections.
Solution Approach 2:
The problematic element (metal layer for silicide formation) is extracted or removed from the process steps applied to first diffusion layers. By not forming metal layers on first diffusion layers, the source of unreacted metal leakage is eliminated while silicide formation continues on second diffusion layers.
3Manufacturing precision
If pixel pitch is reduced for high-definition display, then display quality is enhanced, but metal diffusion risk increases due to closer proximity
Solution Approach 1:
The diffusion layer structure is segmented to create a metal-free zone around light-emitting portions. First diffusion layers without silicide and without overlying metal layers form protective barriers that prevent metal diffusion even when pixel pitch is reduced, enabling high-definition displays without increasing diffusion risk.
Solution Approach 2:
The first diffusion layer without silicide acts as an intermediary barrier between metal layers and light-emitting portions. This intermediate structure prevents direct contact and diffusion pathways, allowing closer spacing of pixels while maintaining protection against metal contamination.
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 configuration effectively suppresses bright spot defects by preventing unnecessary leakage currents and enhances display quality by maintaining high luminance uniformity and reducing pixel pitch, allowing for high-definition displays.
Implementation Method 1
silicide formed by reacting a silicon substrate and metal so as to reduce the contact resistance between the contact metal and the silicon substrate
Implementation Method 2
unreacted metal may diffuse into the silicon substrate to become an unnecessary leakage source
Data Source
AI summary
A display device includes a light-emitting portion and a drive circuit. The drive circuit includes a transistor that drives the light-emitting portion and includes a first diffusion layer and a first contact electrode, the first diffusion layer including no silicide formed in a silicon region, the first contact electrode being electrically connected to the first diffusion layer.