Display Element Capacitance Layout for Fine-Pitch Burn-In Control
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Solution Overview
Problem
As pixel pitch becomes finer in display elements, the capacitance between transistors facing each other across the element isolation region increases, leading to a burn-in phenomenon due to the influence of capacitance on the voltage-current characteristic of the light-emitting units.
Innovation Solution
The drive transistor and write transistor are separated by an element isolation region on a semiconductor substrate, with the capacitance generated between them functioning as part of the capacitance unit, utilizing a shallow trench isolation structure to minimize the impact of capacitance on the display image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel pitch is made finer to improve display resolution, then the display device achieves higher resolution, but the capacitance between transistors increases causing burn-in phenomenon
Solution Approach 1:
The patent converts the harmful parasitic capacitance between transistors into a beneficial component by designing the capacitance unit to utilize this naturally generated capacitance. The capacitance unit is positioned between the drive transistor and write transistor, and the insulating film thickness is optimized (50-200 nm) to ensure that the parasitic capacitance contributes positively to the overall capacitance value, eliminating the need for additional capacitance structures and reducing manufacturing complexity.
Solution Approach 2:
The patent changes the physical parameter of the insulating film thickness to optimize the capacitance characteristics. By controlling the thickness of the insulating film in the capacitance unit to be within 50-200 nm, the patent achieves optimal capacitance values that utilize the parasitic capacitance effect while maintaining stable electrical characteristics and preventing burn-in phenomenon.
2Length of moving object
If the element isolation region is made narrower to reduce pixel pitch, then the display device achieves finer pixel pitch, but the capacitance between transistors increases
Solution Approach 1:
The patent transforms the harmful capacitance effect that arises from narrower element isolation regions into a beneficial feature. The capacitance unit is strategically positioned to exploit the parasitic capacitance between transistors, converting what would normally be a harmful effect into a useful component that helps maintain voltage stability and prevent burn-in.
Solution Approach 2:
The patent introduces an intermediary structure (the capacitance unit with optimized insulating film) between the transistors that mediates the capacitance effect. This intermediary structure controls and optimizes the parasitic capacitance, transforming it from a harmful factor into a beneficial component that stabilizes the electrical characteristics of the display device.
3Reliability
If additional capacitance structures are added to compensate for burn-in, then the display device reduces burn-in effect, but the device complexity increases
Solution Approach 1:
The patent eliminates the need for additional capacitance compensation structures by converting the existing parasitic capacitance into a beneficial component. The capacitance unit utilizes the naturally occurring capacitance between transistors, achieving burn-in resistance without requiring extra complex structures, thereby maintaining device simplicity.
Solution Approach 2:
The patent enables the display device to be self-sufficient by utilizing its own inherent parasitic capacitance to achieve burn-in resistance. The capacitance unit is designed to harvest and utilize the naturally generated capacitance between transistors, eliminating the need for external capacitance compensation structures and reducing manufacturing 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
This configuration reduces the emphasis of burn-in phenomenon by minimizing the change in gate voltage due to capacitive coupling, maintaining consistent current flow through the light-emitting units.
Implementation Method 1
a capacitance generated in a portion where the drive transistor and the write transistor face each other through the element isolation region functions as at least a part of the capacitance unit
Data Source
AI summary
A display element includes a light-emitting unit of a current drive type, and a drive unit that drives the light-emitting unit, in which the drive unit includes a capacitance unit, a drive transistor that causes a current corresponding to a voltage held by the capacitance unit to flow through the light-emitting unit, and a write transistor that writes a signal voltage to the capacitance unit, the drive transistor and the write transistor are formed in a state of being separated by an element isolation region, on a semiconductor substrate, and a capacitance generated in a portion where the drive transistor and the write transistor face each other through the element isolation region functions as at least a part of the capacitance unit.