OLED Display Transistor Surface Roughness Control
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Solution Overview
Problem
Existing organic light emitting diode (OLED) displays face challenges in achieving optimal switching and driving characteristics due to surface roughness differences in semiconductor layers of transistors, which affect the S-factor and overall performance.
Innovation Solution
The OLED display employs a manufacturing method involving the formation of polysilicon semiconductor layers with controlled surface roughness by laser irradiation, where the driving transistor has a higher RMS roughness than the switching transistor, and an insulating layer covers both, improving the switching capability of the switching transistor while maintaining the driving range of the driving transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the semiconductor layer surface roughness is increased to improve switching capability, then the switching speed improves, but the driving range deteriorates
Solution Approach 1:
The patent applies local quality by creating different surface roughness characteristics in different regions of the semiconductor layer. The switching transistor region has a first semiconductor layer with higher RMS roughness (9-15 nm) to improve switching capability, while the driving transistor region has a second semiconductor layer with lower RMS roughness (2-7 nm) to maintain driving range. This spatial differentiation of surface properties allows each transistor type to optimize its performance characteristics independently.
2Reliability
If the RMS roughness of the first semiconductor layer is increased to about 9 nm to about 15 nm, then the switching capability is improved, but the manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent employs parameter changes by systematically controlling the RMS roughness within specific numerical ranges. The first semiconductor layer is engineered to have RMS roughness of 9-15 nm while the second semiconductor layer is controlled to 2-7 nm. These quantified parameter specifications transform the manufacturing process from qualitative to quantitative control, enabling precise reproduction of desired surface characteristics through controlled variable parameters in the laser irradiation process.
3Reliability
If selective laser irradiation is used to create different roughness patterns, then the transistor performance is optimized, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the semiconductor layer formation process into distinct stages and regions. The laser irradiation process is segmented to treat different areas differently: a first region receives laser treatment to create the first semiconductor layer with higher roughness, while a second region receives different laser treatment to create the second semiconductor layer with lower roughness. This segmentation of the manufacturing process allows optimized performance for different transistor types while maintaining a systematic approach to complexity management.
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 switching speed of the switching transistor and maintains a wide driving range for the driving transistor, improving the overall performance and gray expression in OLED displays.
Implementation Method 1
forming a polysilicon layer by irradiating a first laser beam to the amorphous silicon layer
Implementation Method 2
The second region of the polysilicon layer may be re-crystallized after being melted by irradiating the second laser beam thereto
Implementation Method 3
Electrons injected from a cathode as a first electrode and holes injected from an anode as a second electrode may combine in the organic emission layer to generate excitons, and the excitons may emit light while emitting energy
Data Source
AI summary
An organic light emitting diode display includes a substrate, a scan line on the substrate to transfer a scan signal, a data line on the substrate to transfer a data signal, a switching transistor connected with the scan line and the data line, a driving transistor connected with the switching transistor, and an organic light emitting diode electrically connected to the driving transistor. The driving transistor may include a first semiconductor layer, the switching transistor may include a second semiconductor layer, and the first semiconductor layer may have a surface roughness that is greater than that of the second semiconductor layer.