Staggered Oxide Semiconductor Transistor Parasitic Capacitance
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Solution Overview
Problem
Inverted staggered transistors with oxide semiconductor films face issues with parasitic capacitance and oxygen vacancies, leading to signal delay and degradation in display quality, especially with increasing screen size and resolution, and variations in electrical characteristics among transistors.
Innovation Solution
A staggered transistor structure with an oxide semiconductor film, including a channel region overlapping with a gate electrode, and source and drain regions containing specific impurities like hydrogen, boron, and rare gases, is developed, along with a metal oxide film to protect the side surfaces and control oxygen vacancies, enhancing reliability and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an inverted staggered transistor structure is used, then manufacturing simplicity and low cost are achieved, but parasitic capacitance between gate and source/drain electrodes increases causing signal delay
Solution Approach 1:
The patent inverts the conventional transistor structure from inverted staggered to staggered configuration. In the staggered structure, the gate electrode is positioned above the oxide semiconductor film rather than below, which physically separates the gate from the source and drain electrodes, thereby reducing parasitic capacitance and signal delay while maintaining manufacturing feasibility
2Manufacturing precision
If screen size and resolution are increased, then display quality improves, but parasitic capacitance effects become more severe leading to signal delay
Solution Approach 1:
By inverting the transistor structure to staggered configuration, the gate electrode is positioned above the channel region, creating physical separation from source and drain electrodes. This structural inversion reduces parasitic capacitance effects that would otherwise worsen with increased screen size and resolution, enabling high-definition displays without severe signal delay
3Power
If oxygen vacancies are present in the oxide semiconductor film, then carrier generation occurs, but electrical characteristics shift and reliability degrades
Solution Approach 1:
The patent applies local quality by creating distinct regions within the oxide semiconductor film: the channel region is maintained with low oxygen vacancies to ensure stable electrical characteristics and reliability, while source and drain regions are intentionally doped with impurities to generate carriers and reduce contact resistance. This spatial differentiation of oxygen vacancy concentration resolves the contradiction between carrier generation and electrical stability
4Reliability
If source and drain regions have low resistance, then contact resistance with electrodes is reduced, but oxygen vacancies must be increased which affects channel region stability
Solution Approach 1:
The patent implements local quality by selectively controlling oxygen vacancy distribution: source and drain regions contain intentional impurity doping to create low resistance and reduce contact resistance, while the channel region maintains low oxygen vacancy concentration to ensure compositional stability and reliable electrical characteristics. This localized differentiation allows simultaneous optimization of both contact resistance and channel stability
Data Source
AI summary
In a transistor including an oxide semiconductor, a change in electrical characteristics is suppressed and reliability is improved. The transistor includes an oxide semiconductor film over a first insulating film; a second insulating film over the oxide semiconductor film; a gate electrode over the second insulating film; a metal oxide film in contact with a side surface of the second insulating film; and a third insulating film over the oxide semiconductor film, the gate electrode, and the metal oxide film. The oxide semiconductor film includes a channel region overlapping with the gate electrode, a source region in contact with the third insulating film, and a drain region in contact with the third insulating film. The source region and the drain region contain one or more of hydrogen, boron, carbon, nitrogen, fluorine, phosphorus, sulfur, chlorine, titanium, and a rare gas.