Mixed Semiconductor Thin Film Transistor Array for OLED Uniformity
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Solution Overview
Problem
Existing thin film transistor array substrates for OLED display devices face challenges due to the use of a single semiconductor material for both driving and switching transistors, leading to either poor uniformity or low mobility, which negatively impacts display quality.
Innovation Solution
The use of different semiconductor materials for the active layers of driving and switching transistors, with poly-silicon for high mobility and metal oxide semiconductor for better uniformity, optimized by structuring the thin film transistor array substrate with specific layers and processing steps to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If poly-silicon material is used as the active layer of the thin film transistor, then the mobility is high, but the leakage current is large and the uniformity is poor
Solution Approach 1:
The patent applies different semiconductor materials to different transistor types within the same display device. Specifically, poly-silicon is used for switching transistors where high mobility is critical for fast signal transmission, while metal oxide semiconductor is used for driving transistors where uniformity and low leakage current are essential for stable light emission. This localized material selection resolves the contradiction by matching material properties to functional requirements of different circuit components.
2Reliability
If metal oxide semiconductor material is used as the active layer of the thin film transistor, then the uniformity is better, but the mobility is low
Solution Approach 1:
The patent strategically assigns metal oxide semiconductor material to driving transistors where uniformity is the priority for maintaining consistent luminance across pixels, while accepting lower mobility as a trade-off. The switching transistors use poly-silicon to compensate for the lower mobility of metal oxide semiconductor, ensuring fast switching performance. This spatial differentiation of material properties resolves the mobility-uniformity contradiction.
3Ease of manufacture
If a single semiconductor material is used for both driving transistor and switching transistor, then the manufacturing process is simplified, but the display quality deteriorates due to enlarged disadvantages of the material
Solution Approach 1:
The patent implements a mixed-material architecture where different semiconductor materials are used in different transistor locations within the same array substrate. This approach prioritizes display quality by optimizing each transistor type's material selection for its specific function, while maintaining a relatively streamlined manufacturing process through the use of sequential deposition and selective etching techniques. The local differentiation of material properties directly addresses the display quality issue.
4Reliability
If different semiconductor materials are used for driving transistor and switching transistor, then the electric performance is optimized, but the device complexity increases
Solution Approach 1:
The patent optimizes electric performance by selecting poly-silicon for switching transistors to achieve fast switching speeds and metal oxide semiconductor for driving transistors to achieve low leakage current and high uniformity. The increased device complexity is managed through a systematic fabrication process that deposits material layers sequentially and uses photolithographic patterning to define different active regions, thereby organizing the complexity in a manufacturable and maintainable manner.
Data Source
AI summary
The present disclosure discloses a thin film transistor array substrate including an active layer disposed on a base substrate, wherein the active layer includes a first active region and a second active region located in a same structural layer, the first active region has a material comprising poly-silicon, and includes a first channel region, and a first source region and a first drain region that are located at both sides of the first channel region, respectively, the first source region having a first contact layer disposed thereon, the first drain region having a second contact layer disposed thereon, and materials of both the first and second contact layers being boron-doped poly-silicon; and the second active region has a material comprising metal oxide semiconductor, and includes a second channel region and a second source region and a second drain region that are located at both sides of the second channel region, respectively. The present disclosure also discloses a preparing method for the thin film transistor array substrate as mentioned above, and an OLED display device including the array substrate.