TFT Backplate Gate Isolation Layer Differentiation
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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 achieving fast charge and discharge and precise current control, respectively, due to shared manufacturing processes and materials.
Innovation Solution
A TFT backplate structure is designed with distinct gate isolation layers for switch and drive TFTs, utilizing different materials (SiOx, Al2O3, SiNx, or their mixtures) and thicknesses (2000 Å and 4000 Å) to create distinct electrical properties, allowing for separate optimization of subthreshold swing for each type of TFT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
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 optimized for different functions
Solution Approach 1:
The patent applies local quality by forming different gate isolation layer structures at different locations. Specifically, the drive TFT region receives a first gate isolation layer with specific material composition and thickness, while the switch TFT region receives a second gate isolation layer with different material composition and thickness. This allows each TFT type to have optimized electrical properties tailored to its specific function without requiring completely separate manufacturing processes.
Solution Approach 2:
The manufacturing process is segmented into region-specific steps. After forming the common gate electrodes, the process divides the substrate into drive TFT regions and switch TFT regions, applying different gate isolation layer treatments to each region. This segmentation enables differentiated electrical properties while maintaining overall process integration.
2Reliability
If different gate isolation layer structures are used for switch TFT and drive TFT, then electrical properties can be optimized, but the manufacturing process complexity increases
Solution Approach 1:
The patent employs preliminary action by forming a common base layer (first gate isolation layer) across the entire substrate before creating the differentiated structures. This preliminary uniform layer simplifies subsequent processing, as the differentiation is achieved through selective removal or modification in specific regions rather than forming entirely separate structures from scratch.
Solution Approach 2:
The process extracts the differentiation step from the common manufacturing flow by selectively removing portions of the first gate isolation layer in switch TFT regions or selectively forming the second gate isolation layer only in switch TFT regions. This extraction approach allows differentiation without requiring completely separate manufacturing lines.
3Reliability
If the Etching Stopper Layer structure is used to protect the oxide semiconductor layer, then stability is improved, but coupling capacitance increases which reduces manufacturing yield
Solution Approach 1:
The patent extracts the protective function from a separate etching stopper layer by integrating protection directly into the gate isolation layer structure itself. The gate isolation layer is designed with sufficient thickness and appropriate material properties to serve both as an electrical isolation layer and as protection for the oxide semiconductor layer, eliminating the need for an additional etching stopper layer.
Solution Approach 2:
The protective function and the gate isolation function are merged into a single integrated structure. The gate isolation layer simultaneously provides electrical isolation between gate and channel regions and protects the underlying oxide semiconductor layer from etching damage, reducing the total number of layers and manufacturing steps.
Data Source
AI summary
A TFT backplate structure and a manufacture method thereof are provided. The TFT backplate structure includes a switch TFT (T1) and a drive TFT (T2). The switch TFT (T1) is constructed by a first source electrode/a first drain electrode (61), a first gate electrode (21), and a first etching stopper layer (51), a first semiconductor layer (41), a first gate isolation layer (31) sandwiched in between. The drive TFT (T2) is constructed by a second source electrode/a second drain electrode (62), a second gate electrode (22), and a second etching stopper layer (52), a second semiconductor layer (42), a second gate isolation layer (32) sandwiched in between. The materials or the thicknesses of the first gate isolation layer (31) and the second gate isolation layer (32) are different. Accordingly, the electrical properties of the switch TFT (T1) and the drive TFT (T2) are different.