EL Display Transistor Taper Angle Control
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Solution Overview
Problem
The existing electro-luminescence display devices face issues with taper angle deviations in transistor channel areas, leading to threshold voltage deviations and kickback voltages, which affect image quality and brightness uniformity, and degrade the performance of conventional compensation circuits.
Innovation Solution
The solution involves an electro-luminescence display device with pixels having driving and switching transistors with different channel area sizes, where the taper angle deviation between the semiconductor layers of these transistors is controlled to be equal to or less than 10° through an O2 gas flow rate adjustment during the dry etching process, using a low-temperature poly silicon layer and a mixture gas including O2, CF4, SF6, He, HCl, and Cl2 for dry etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different channel area sizes are used for driving transistor and switching transistor, then device functionality is improved, but taper angle deviation increases leading to threshold voltage deviation
Solution Approach 1:
The patent applies local quality by adjusting the O2 gas flow rate specifically during the dry etching process of the semiconductor layer to control the taper angle. By optimizing the gas flow rate distribution and etching conditions in different regions, the patent achieves uniform taper angles (≤10°) across transistors with different channel area sizes, thereby reducing threshold voltage deviation while maintaining device functionality.
2Reliability
If taper angle deviation is reduced to ≤10°, then threshold voltage deviation and kickback voltage are reduced, but this requires precise control of O2 gas flow rate during dry etching
Solution Approach 1:
The patent applies parameter changes by optimizing the O2 gas flow rate during the dry etching process. By adjusting this critical parameter, the patent achieves uniform taper angles across different transistor types, which reduces threshold voltage deviation and improves brightness uniformity. This parameter optimization approach balances reliability improvement with manageable process complexity.
3Ease of manufacture
If conventional dry etching is used without O2 gas flow rate adjustment, then manufacturing process is simpler, but taper angle deviation exceeds 10° causing threshold voltage deviation
Solution Approach 1:
The patent modifies the dry etching process by adjusting the O2 gas flow rate parameter. This change improves taper angle uniformity to ≤10° without significantly complicating the manufacturing process. The optimized gas flow rate enables better etching control and more uniform semiconductor layer profiles across different transistor channel areas.
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 reduces threshold voltage deviations and kickback voltages, improving brightness uniformity and image retention characteristics by minimizing taper angle deviations, thereby enhancing the overall image quality and compensation performance.
Implementation Method 1
patterning a taper angle of channel areas of a driving transistor and a taper angle of channel areas of a switching transistor by a dry etching process with at least 30% of O2 gas flow rate
Data Source
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AI summary
An electro-luminescence display device comprising: a pixel (P) comprising: an electro-luminescence diode (ELD); a driving transistor (DT) configured to supply a current to the electro-luminescence diode; and a switching transistor (ST) configured to switch a signal supplied to the driving transistor, wherein a size of a channel area of the driving transistor is different from a size of a channel area of the switching transistor, and wherein a taper angle deviation of the channel areas of the driving transistor and the switching transistor is equal to or less than 10°.