Dual-Gate Oxide Semiconductor Transistors With Stable Low Off-State Current
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Solution Overview
Problem
Transistors using oxide semiconductors face challenges with low field-effect mobility, high off-state current, and unstable electrical characteristics due to variations in stoichiometric composition and hydrogen bonding, which are exacerbated by the demand for higher definition and larger screens in display devices.
Innovation Solution
A semiconductor device is developed with transistors featuring an intrinsic or substantially intrinsic oxide semiconductor layer containing a crystalline region in the surface portion, utilizing a dual-gate structure with conductive films on opposite sides separated by insulating films to control channel formation and reduce off-state current, and employing a manufacturing method that includes dehydration or dehydrogenation to stabilize the oxide semiconductor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If oxide semiconductor is used to form transistor, then field-effect mobility is improved compared to amorphous silicon, but field-effect mobility remains lower than polycrystalline silicon
Solution Approach 1:
The patent changes the physical and chemical parameters of the oxide semiconductor by controlling oxygen content (creating oxygen deficiency) and carbon content (adding carbon atoms) to transform the material from amorphous to crystalline structure, achieving high field-effect mobility while maintaining electrical stability
Solution Approach 2:
The patent creates a composite structure by combining oxide semiconductor with specific carbon content and controlled oxygen deficiency, forming a new material phase that exhibits both high mobility and stable electrical characteristics
2Measurement precision
If higher definition display is implemented, then image quality is improved, but the number of pixels increases significantly reducing writing time per pixel
Solution Approach 1:
The patent applies preliminary anti-action by forming a crystalline region in the surface portion of the oxide semiconductor layer before transistor operation, which pre-establishes high mobility channels that enable fast switching speeds necessary for high-definition displays with reduced writing time per pixel
3Ease of manufacture
If oxide semiconductor layer is formed with standard composition, then manufacturing is simplified, but electrical conductivity becomes unstable due to oxygen excess or deficiency
Solution Approach 1:
The patent deliberately changes the compositional parameters by introducing controlled oxygen deficiency and carbon content into the oxide semiconductor layer, transforming it into a crystalline phase that exhibits stable electrical conductivity while remaining compatible with existing manufacturing processes
4Ease of manufacture
If hydrogen enters oxide semiconductor during thin film formation, then film formation is facilitated, but O-H bonds form creating electron donors that change electric conductivity
Solution Approach 1:
The patent converts the harmful effect of hydrogen (which forms unstable O-H bonds) into a beneficial outcome by controlling the overall composition to create a crystalline oxide semiconductor structure where the hydrogen's presence is accommodated within a stable crystalline framework, eliminating the instability caused by O-H bonding
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
The solution enhances transistor performance with improved dynamic characteristics, reduced off-state current, and stable electrical properties, enabling higher operation speed and reduced power consumption, suitable for large and high-definition display devices.
Implementation Method 1
performing dehydration or dehydrogenation to stabilize the oxide semiconductor
Implementation Method 2
performing dehydration or dehydrogenation to stabilize the oxide semiconductor
Implementation Method 3
an oxide semiconductor layer which is intrinsic or substantially intrinsic and includes a crystalline region in a surface portion
Data Source
AI summary
An oxide semiconductor layer which is intrinsic or substantially intrinsic and includes a crystalline region in a surface portion of the oxide semiconductor layer is used for the transistors. An intrinsic or substantially intrinsic semiconductor from which an impurity which is to be an electron donor (donor) is removed from an oxide semiconductor and which has a larger energy gap than a silicon semiconductor is used. Electrical characteristics of the transistors can be controlled by controlling the potential of a pair of conductive films which are provided on opposite sides from each other with respect to the oxide semiconductor layer, each with an insulating film arranged therebetween, so that the position of a channel formed in the oxide semiconductor layer is determined.