Oxide Semiconductor Transistors for Large-Substrate Display Manufacturing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current display devices face challenges in manufacturing large-sized substrates with high productivity and reduced production costs, as existing methods for transistor formation on insulating surfaces, such as laser irradiation, are limited in area and time, and require multiple transistors with varying characteristics for pixel and driver circuits, increasing complexity and cost.
Innovation Solution
A display device with a pixel portion and driver circuit formed over one substrate, utilizing transistors with oxide semiconductor films of different compositions and channel lengths, where the first transistor has a longer channel length than the second transistor, and the third transistor is in contact with the side surface of the second transistor, allowing for high image quality and reduced external connection terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser irradiation is used for crystallization process of polysilicon, then transistor manufacturing is enabled, but irradiation area per unit time is limited and processing large-sized substrates becomes difficult
Solution Approach 1:
The patent replaces the mechanical laser irradiation system with a sputtering-based oxide semiconductor film formation process. Instead of using laser light to crystallize polysilicon, the invention forms transistors using oxide semiconductor films deposited by sputtering, eliminating the area and time limitations of laser processing while enabling efficient manufacturing on large-sized substrates
Solution Approach 2:
The patent changes the material parameter from polysilicon to oxide semiconductor, and the processing method parameter from laser irradiation to sputtering deposition. This parameter change enables transistor formation without the limitations of laser processing area and time, allowing high-productivity manufacturing on large substrates
2Reliability
If multiple transistors with varying characteristics are used for pixel and driver circuits, then circuit performance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent makes oxide semiconductor transistors universal for both pixel circuits and driver circuits by adjusting only the channel length parameter. A single transistor design with variable channel length replaces the need for multiple transistor types, simplifying manufacturing while maintaining the ability to provide different performance characteristics for different circuit functions
Solution Approach 2:
The patent applies local quality by varying the channel length of oxide semiconductor transistors according to their specific circuit function. Pixel transistors and driver circuit transistors have different channel lengths optimized for their respective roles, allowing each transistor to have locally optimized characteristics while using the same base material and fabrication process
Data Source
AI summary
To provide a display device in which plural kinds of circuits are formed over one substrate and plural kinds of transistors corresponding to characteristics of the plural kinds of circuits are provided. The display device includes a pixel portion and a driver circuit that drives the pixel portion over one substrate. The pixel portion includes a first transistor including a first oxide semiconductor film. The driver circuit includes a second transistor including a second oxide semiconductor film. The first oxide semiconductor film and the second oxide semiconductor film are formed over one insulating surface. A channel length of the first transistor is longer than a channel length of the second transistor. The channel length of the first transistor is greater than or equal to 2.5 micrometer.