GOA TFT Carrier Mobility via Dual Oxide Semiconductor Layers
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Solution Overview
Problem
Existing OLED display technologies face limitations in increasing carrier mobility of Thin Film Transistors (TFTs) at Gate Driver on Array (GOA) regions without compromising performance stability, with current methods only marginally increasing mobility from 10 cm2/(V·S) to 11-12 cm2/(V·S).
Innovation Solution
A display substrate design incorporating a first oxide semiconductor layer with lower carrier mobility between a second oxide semiconductor layer and the base substrate, where the second oxide semiconductor layer is made of high mobility materials like IGZYO or IGTO, with specific In:Ga:Zn:Sn ratios and oxygen content, to enhance carrier mobility while maintaining stability, allowing for a narrower TFT width and bezel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single IGZO layer is used as the active layer of TFT at the GOA region, then the manufacturing process is simple, but the carrier mobility is insufficient (only 10 cm2/(V·S))
Solution Approach 1:
The patent uses a composite structure consisting of a first oxide semiconductor layer (IGZO) and a second oxide semiconductor layer (IGZYO or IGTO) with different material compositions. The first layer provides stability while the second layer provides high carrier mobility (>30 cm2/(V·S)), achieving both manufacturing feasibility and performance requirements through material composition optimization rather than process complexity
Solution Approach 2:
The active layer is segmented into two distinct oxide semiconductor layers with different functions: the first layer (IGZO) serves as the base layer with lower carrier mobility but good stability, while the second layer (IGZYO/IGTO) serves as the high-mobility layer. This segmentation allows each layer to optimize its properties independently, achieving overall carrier mobility of 20.5-30.2 cm2/(V·S) while maintaining manufacturing simplicity
2Productivity
If the carrier mobility of TFT at GOA region is increased to improve display performance, then the bezel width can be reduced, but the performance stability deteriorates
Solution Approach 1:
The patent applies local quality by creating different oxide semiconductor layers with specific compositions at different positions within the active layer. The first layer (IGZO) has composition In:Ga:Zn=1:1:1 and serves as a stable base, while the second layer (IGZYO or IGTO) has optimized composition (In:Ga:Zn:Sn=6:1:4:1 or In:Ga:Zn=1:1:1 with oxygen content 10-35%) to provide high carrier mobility. This local differentiation allows high performance in the second layer while the first layer maintains overall stability
Solution Approach 2:
The composite structure of IGZO and IGZYO/IGTO layers creates a material system where the first layer provides structural stability and the second layer provides high carrier mobility. The specific oxygen content control (10-35% in second layer) and element ratios (In:Ga:Zn:Sn=6:1:4:1) create a composite material system that achieves carrier mobility of 20.5-30.2 cm2/(V·S) while maintaining performance stability under various operating conditions
3Reliability
If two IGZO layers are used to increase carrier mobility, then the manufacturing process becomes more complex, but the carrier mobility increase is limited (only to 11-12 cm2/(V·S))
Solution Approach 1:
The patent changes the material composition parameters of the oxide semiconductor layers, specifically using IGZYO or IGTO for the second layer instead of IGZO. The composition ratio (In:Ga:Zn:Sn=6:1:4:1) and oxygen content (10-35%) are optimized to achieve carrier mobility >30 cm2/(V·S) in the second layer, significantly higher than the 11-12 cm2/(V·S) achieved with two IGZO layers. This parameter optimization achieves high carrier mobility without increasing structural complexity
Solution Approach 2:
The patent creates a composite material system where the second oxide semiconductor layer uses IGZYO or IGTO materials with specific composition ratios (In:Ga:Zn:Sn=6:1:4:1) and oxygen content (10-35%). This composite approach achieves carrier mobility of 20.5-30.2 cm2/(V·S) in the TFT, significantly higher than the 11-12 cm2/(V·S) limit of dual IGZO structures, while maintaining a manageable two-layer structure
Data Source
AI summary
The present disclosure relates to the field of display technology, and provides a display substrate, its manufacturing method, and a display device. The display substrate includes a display region and a GOA region. An active layer of a TFT at the GOA region at least includes a first oxide semiconductor layer and a second oxide semiconductor layer arranged on the first oxide semiconductor layer, and the first oxide semiconductor layer is arranged between the second oxide semiconductor layer and a base substrate of the display substrate and has a carrier mobility of smaller than the second oxide semiconductor layer.