Oxide Semiconductor Transistor Off Current Reduction
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Solution Overview
Problem
Current display devices with oxide semiconductor transistors have off currents that are not sufficiently low to meet the requirements for reduced power consumption, especially for still image display where power consumption needs to be minimized.
Innovation Solution
Incorporating a high-purity oxide semiconductor with a hydrogen concentration of 5×10^19/cm^3 or less into the transistors of the display device, which reduces off current to 1×10^-13 A or lower, and using a driver circuit that stops signal output during still image display to further reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional oxide semiconductor transistors are used in display devices, then the device can operate with standard power consumption levels, but the off current remains too high (above 1×10^-13 A) to achieve sufficient power reduction for still image display
Solution Approach 1:
The patent applies parameter changes by precisely controlling the hydrogen concentration in the oxide semiconductor layer to 5×10^19/cm³ or less. This specific parameter change transforms the semiconductor from having high off current (conventional level) to extremely low off current (1×10^-13 A or lower), enabling the display device to achieve ultra-low power consumption during still image display while maintaining reliable transistor operation
Solution Approach 2:
The patent creates an inert environment within the oxide semiconductor layer by eliminating hydrogen impurities, which act as carriers and disrupt normal operation. By achieving a hydrogen concentration of 5×10^19/cm³ or less, the oxide semiconductor becomes intrinsic or substantially intrinsic, creating a clean, inert semiconductor environment that enables extremely low off current and stable transistor performance for power-efficient display operation
2Use of energy by moving object
If the transistor off current is reduced to 1×10^-13 A or lower using high-purity oxide semiconductor, then power consumption during still image display is reduced, but the manufacturing precision requirement increases due to the need to control hydrogen concentration at 5×10^19/cm³ or less
Solution Approach 1:
The patent establishes a specific parameter threshold (hydrogen concentration ≤5×10^19/cm³) that, when achieved, simultaneously delivers both ultra-low off current (≤1×10^-13 A) and acceptable manufacturing feasibility. This parameter change defines a target zone that balances the competing demands of manufacturing precision and device performance
Solution Approach 2:
The patent employs a sputtering method with a purified oxide semiconductor target that can be produced through conventional purification processes. Rather than requiring extremely complex or expensive manufacturing equipment, the solution uses a purified target material that can be manufactured at reasonable cost, making the high-precision hydrogen concentration control achievable through standard industrial processes
Data Source
AI summary
A display device includes a pixel portion including a plurality of pixels each including a first transistor, a second transistor, and a light-emitting element, in which a gate of the first transistor is electrically connected to a scan line, one of a source and a drain of the first transistor is electrically connected to a signal line, and the other of them is electrically connected to a gate of the second transistor; one of a source and a drain of the second transistor is electrically connected to a power supply line and the other of them is electrically connected to the light-emitting element, and the first transistor includes an oxide semiconductor layer. A period when the display device displays a still image includes a period in which output of a signal to all the scan lines in the pixel portion is stopped.