TFT Backplate With Variable Gate Isolation Thickness
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Solution Overview
Problem
Current oxide semiconductor TFT backplate structures lack differentiation in electrical properties between switch TFTs and drive TFTs, which are essential for optimal performance in flat panel displays, as they share the same structure and electrical characteristics, failing to meet the distinct demands of fast charge/discharge and precise current control.
Innovation Solution
A TFT backplate structure is designed with distinct configurations for switch and drive TFTs, utilizing a first and second gate isolation layer, etching stopper layers, and oxide semiconductor layers to create separate electrical properties, where the switch TFT has a smaller subthreshold swing for fast charge/discharge and the drive TFT has a larger subthreshold swing for precise current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the same manufacture process is used for both switch TFT and drive TFT, then the manufacturing complexity is reduced, but the electrical properties cannot be differentiated to meet different functional demands
Solution Approach 1:
The patent applies local quality by making the gate isolation layer thickness location-specific: the first gate isolation layer (for switch TFT) has a first thickness, while the second gate isolation layer (for drive TFT) has a second thickness different from the first. This localized variation in structural parameter enables different electrical properties (subthreshold swing characteristics) for switch and drive TFTs without requiring completely different manufacture processes, thus resolving the contradiction between adaptability and manufacturing complexity.
2Ease of manufacture
If the gate isolation layer has uniform thickness, then the manufacture process is simpler, but the electrical properties of switch TFT and drive TFT cannot be optimized for their respective functions
Solution Approach 1:
The gate isolation layer is designed with local quality variation where different regions have different thicknesses. The first gate isolation layer region has a first thickness and the second gate isolation layer region has a second thickness, allowing optimization of electrical properties for specific functions (switching speed vs. current control precision) while maintaining a relatively simple uniform manufacturing approach through selective thickness control in different locations.
3Reliability
If switch TFT and drive TFT have the same structure, then the device complexity is reduced, but the performance requirements for fast charge/discharge and precise current control cannot be simultaneously met
Solution Approach 1:
The patent implements local quality by creating structure-specific thickness variations in gate isolation layers. The switch TFT region receives a gate isolation layer with a first thickness optimized for fast charge/discharge, while the drive TFT region receives a gate isolation layer with a second thickness optimized for precise current control. This localized differentiation achieves functional performance optimization without requiring completely different TFT structures, thus resolving the contradiction between reliability and device complexity.
Data Source
AI summary
The present invention provides a TFT backplate structure and a manufacture method thereof. The TFT backplate structure comprises a switch TFT (T1) and a drive TFT (T2). The switch TFT (T1) is constructed by a first source/a first drain (61), a first gate (21), and a first etching stopper layer (51), a first oxide semiconductor layer (41), a first gate isolation layer (31) sandwiched in between. The drive TFT (T2) is constructed by a second source/a second drain (62), a second gate (22), and a second oxide semiconductor layer (42), a first etching stopper layer (51), a second gate isolation layer (32) sandwiched in between. The electrical properties of the switch TFT (T1) and the drive TFT (T2) are different. The switch TFT has smaller subthreshold swing to achieve fast charge and discharge, and the drive TFT has relatively larger subthreshold swing for controlling the current and the grey scale more precisely.