Dual-Layer Light Shielding for Oxide TFT Display Stability
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Solution Overview
Problem
Transistors using oxide semiconductors as channels are prone to characteristic fluctuations due to light exposure, which can hinder high-definition displays, and the light-shielding layers in existing configurations are insufficient to prevent this issue, especially when combined with low-temperature polysilicon transistors in peripheral circuits.
Innovation Solution
A display device design featuring a dual-layer light-shielding structure, with a first light-shielding metal layer under the oxide semiconductor and a second layer covering its top and side surfaces, along with a thicker light-shielding layer in peripheral transistors to prevent light exposure and stabilize oxide semiconductor characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light-shielding layer is provided under the oxide semiconductor transistor to prevent light exposure, then the characteristic fluctuation of the oxide semiconductor is suppressed, but the light-shielding layer thickness must be increased which conflicts with the gate electrode thickness requirement of LTPS transistors in peripheral circuits
Solution Approach 1:
The light-shielding layer is divided into two separate metal layers (first light-shielding metal layer and second light-shielding metal layer) instead of using a single thick layer. This segmentation allows each layer to have optimized thickness for its specific function while achieving cumulative light-shielding effectiveness.
Solution Approach 2:
Different regions of the light-shielding structure have different thicknesses and positions tailored to their specific requirements. The first light-shielding metal layer is positioned under the oxide semiconductor transistor where maximum shielding is needed, while the second layer is positioned over the LTPS transistor gate electrode where thinner protection suffices.
2Manufacturing precision
If the pixel size is reduced to achieve high-definition displays, then the display resolution is improved, but the opening ratio of the pixel is reduced due to the arrangement of metal and semiconductor layers
Solution Approach 1:
The light-shielding function is distributed across multiple layers in the vertical dimension rather than requiring increased horizontal area. This allows the pixel opening ratio to be maintained while still providing sufficient light shielding through the stacked metal layer configuration.
3Ease of manufacture
If the gate electrode thickness of LTPS transistor is reduced to meet design requirements, then the transistor performance is optimized, but the light-shielding layer of the same thickness becomes insufficient to prevent light exposure
Solution Approach 1:
The light-shielding structure uses a composite of two metal layers instead of a single material layer. This composite structure provides enhanced light-shielding capability compared to a single layer of equivalent total thickness, allowing thin gate electrodes to coexist with effective light shielding.
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 dual-layer light-shielding structure effectively suppresses characteristic fluctuations in oxide semiconductor transistors, enabling high-definition displays while maintaining stable operation of both pixel and peripheral circuits.
Implementation Method 1
a light-shielding layer provided between the substrate and the oxide semiconductor layer
Data Source
AI summary
A display device includes a substrate, a first transistor including an oxide semiconductor layer, a first gate insulating layer, and a first gate electrode, the first transistor being provided in a display region, and a light-shielding layer provided between the substrate and the oxide semiconductor layer. The light-shielding layer includes a first light-shielding metal layer and a second light-shielding metal layer. The first light-shielding metal is provided between the substrate and the oxide semiconductor layer. The second light-shielding metal layer covers the top surface and side surface of the first light-shielding metal layer and faces the oxide semiconductor layer.