Resistance-Tuned Oxide-Semiconductor TFTs for Pixel-Driver Integration
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Solution Overview
Problem
Existing thin film transistors (TFTs) face challenges in achieving high operation speed while maintaining stable electric characteristics, particularly in driver circuits, due to issues such as low on-off ratio and increased capacity load when channel length is reduced or channel width is increased, and the need for different circuit types like pixel and driver circuits to be integrated on a single substrate without complicating the process or increasing costs.
Innovation Solution
The design incorporates bottom-gate thin film transistors with light-transmitting conductive layers for electrodes and semiconductor layers, using materials with varying resistance values for different circuit types, and includes conductive layers to reduce contact resistance, along with specific manufacturing processes like dehydration or dehydrogenation of oxide semiconductor layers to achieve stable and high-speed operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the channel length is reduced to increase operation speed, then the operation speed is improved, but the switching characteristic (on-off ratio) is lowered
Solution Approach 1:
The patent changes the material composition of the semiconductor layer from conventional semiconductors to oxide semiconductors with specific resistance values (10^3 to 10^8 ohm·cm), which fundamentally alters the electrical characteristics to achieve both high speed and high on-off ratio that cannot be achieved by simple geometric parameter changes alone
2Speed
If the channel width is increased to improve operation speed, then the operation speed is improved, but the capacity load is increased
Solution Approach 1:
The patent utilizes the unique property of oxide semiconductors with high resistance values to achieve high operation speed with lower capacity load compared to conventional semiconductors, as the high resistance material inherently reduces parasitic capacitance effects
3Ease of manufacture
If different circuit types (pixel and driver circuits) are integrated on a single substrate, then manufacturing cost is reduced, but the process complexity increases
Solution Approach 1:
The patent applies different resistance value ranges of oxide semiconductors to different circuit regions: higher resistance (10^6 to 10^8 ohm·cm) for pixel circuits requiring low leakage, and lower resistance (10^3 to 10^6 ohm·cm) for driver circuits requiring high drive current, allowing single-substrate integration with optimized performance for each circuit type
Solution Approach 2:
By controlling the resistance value parameter of the oxide semiconductor within specific ranges, the patent enables a single material system to satisfy the contradictory requirements of different circuit types (low leakage for pixels vs. high current drive for drivers) without requiring different materials or complex additional processing steps
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
This approach enables the formation of thin film transistors with improved operation speed and stability, reducing manufacturing complexity and costs, while maintaining high aperture ratios in display devices by using light-transmitting materials and optimizing resistance values for different circuit components.
Implementation Method 1
subjecting the first oxide semiconductor layer and the second oxide semiconductor layer to dehydration or dehydrogenation by heat treatment
Implementation Method 2
subjecting the first oxide semiconductor layer and the second oxide semiconductor layer to dehydration or dehydrogenation by heat treatment
Data Source
AI summary
The semiconductor device includes a driver circuit portion including a driver circuit and a pixel portion including a pixel. The pixel includes a gate electrode layer having a light-transmitting property, a gate insulating layer, a source electrode layer and a drain electrode layer each having a light-transmitting property provided over the gate insulating layer, an oxide semiconductor layer covering top surfaces and side surfaces of the source electrode layer and the drain electrode layer and provided over the gate electrode layer with the gate insulating layer therebetween, a conductive layer provided over part of the oxide semiconductor layer and having a lower resistance than the source electrode layer and the drain electrode layer, and an oxide insulating layer in contact with part of the oxide semiconductor layer.