Semiconductor Device With Localized Insulating Layers For Stable Capacitance
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Solution Overview
Problem
Display devices face challenges in improving image quality and reducing electricity consumption due to voltage dependence of capacitance in pixel areas, which degrades image quality and increases power usage.
Innovation Solution
A semiconductor device with a specific structure comprising insulating substrates, thin-film transistors, and capacitors, where the layer thickness of insulating layers is varied between pixel and peripheral circuit areas to control hydrogen diffusion and carrier density, thereby reducing voltage dependence and enhancing image quality while minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the capacitance of the capacitor has voltage dependence, then the device can operate with standard capacitor design, but the image quality in the pixel area is degraded
Solution Approach 1:
The patent applies different insulating layer thicknesses in different regions: a first insulating layer with thickness of 50-150 nm in the pixel area and a second insulating layer with thickness of 150-300 nm in the peripheral circuit area. This local differentiation creates voltage-independent capacitance in the pixel area while maintaining standard capacitor design elsewhere, resolving the contradiction between ease of manufacture and image quality.
2Ease of manufacture
If the layer thickness of insulating layers is uniform across all areas, then the manufacturing process is simplified, but the threshold voltage cannot be differentiated between pixel and peripheral circuit transistors
Solution Approach 1:
The patent implements local quality by setting the first insulating layer thickness to 50-150 nm in the pixel area and the second insulating layer thickness to 150-300 nm in the peripheral circuit area. This regional differentiation enables precise threshold voltage control for different transistor types while maintaining a relatively simple two-layer manufacturing process.
Solution Approach 2:
The patent changes the physical parameter of insulating layer thickness to control threshold voltage. By adjusting the thickness parameter differently in pixel and peripheral circuit areas, the patent achieves distinct threshold voltage characteristics (lower for pixel TFTs, higher for peripheral TFTs) without complicating the overall manufacturing process.
3Ease of manufacture
If hydrogen diffusion is not controlled, then the manufacturing process is simpler, but the carrier density and threshold voltage become unstable
Solution Approach 1:
The patent uses local quality by creating a nitrogen-rich insulating layer (first insulating layer with 30-70 at% nitrogen) specifically in the pixel area to control hydrogen diffusion. This localized approach stabilizes carrier density and threshold voltage where needed without adding complex hydrogen diffusion control measures across the entire device.
Solution Approach 2:
The patent introduces a nitrogen-containing insulating layer as an intermediary between the substrate and the oxide semiconductor layer. This intermediary layer acts as a hydrogen diffusion barrier, preventing hydrogen from reaching the semiconductor layer and thereby stabilizing carrier density and threshold voltage while maintaining manufacturing simplicity.
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 effectively maintains stable capacitance regardless of voltage, improving image quality and reducing electricity consumption by differentiating threshold voltages between thin-film transistors and capacitors, thus optimizing the performance of display devices.
Implementation Method 1
a first insulating layer which is provided on the insulating substrate and includes at least nitrogen
Implementation Method 2
a second insulating layer at least provided on the first insulating layer of the peripheral circuit area
Data Source
AI summary
According to one embodiment, a semiconductor device includes an insulating substrate including a pixel area and a peripheral circuit area around the pixel area, a first insulating layer which is provided on the insulating substrate and includes at least nitrogen, a second insulating layer at least provided on the first insulating layer of the peripheral circuit area, a first thin-film transistor which is provided above the first insulating layer of the pixel area and includes a first oxide semiconductor layer, and a second thin-film transistor which is provided on the second insulating layer of the peripheral circuit area and includes a second oxide semiconductor layer. The second insulating layer in the pixel area is thinner than that in the peripheral circuit area.