Multi-step Groove Thin Film Transistor Substrate for Flexible Display Alignment
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Solution Overview
Problem
Flexible displays using plastic substrates face challenges in thin-film transistor alignment due to thermal contraction, leading to accuracy issues and product reliability problems, as existing self-aligned imprint lithography methods are complex and limited by undercutting and surface treatment difficulties.
Innovation Solution
A thin film transistor substrate with a multi-step structure featuring grooves of different depths, allowing for self-alignment of gate and data lines, and the formation of thin film transistors with active layers separated by data lines, eliminating the need for undercut structures and simplifying the assembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plastic substrate is used for flexible display, then flexibility and durability are improved, but thermal contraction causes alignment accuracy to deteriorate
Solution Approach 1:
The patent introduces a multi-step structure with grooves of different depths on the substrate surface. This structural parameter change creates physical reference levels that enable accurate alignment of thin film layers despite thermal contraction of the plastic substrate, resolving the contradiction between flexibility and alignment precision
Solution Approach 2:
The multi-step groove structure serves as a self-aligning feature that automatically guides the positioning of gate and data lines during fabrication. The different depth levels create natural reference planes that eliminate the need for complex external alignment processes, maintaining precision while using flexible plastic substrates
2Manufacturing precision
If self-aligned imprint lithography is used, then alignment accuracy is improved, but process complexity increases due to multi-stepped resist and undercutting requirements
Solution Approach 1:
The patent removes the complex multi-stepped resist process and undercutting steps from the fabrication sequence. By using the multi-step groove structure as the primary alignment reference, the method extracts and eliminates unnecessary process steps, achieving self-alignment through the substrate structure itself rather than through complex resist patterning
Solution Approach 2:
Instead of using complex resist structures to create alignment references, the patent inverts the approach by using the substrate groove structure itself as the alignment reference. This reversal simplifies the overall process by eliminating the need for multi-stepped resist and undercutting operations
3Manufacturing precision
If undercut structure is used for gate line patterning, then alignment is achieved, but gate dielectric layer becomes floating and reliability deteriorates
Solution Approach 1:
The patent converts the potential harm of floating gate dielectric layers into a benefit by using the multi-step groove structure to provide mechanical support and anchoring. The groove walls serve as physical anchors that prevent the gate dielectric layer from floating, while still achieving precise alignment through the same groove structure
Data Source
AI summary
A thin film transistor substrate and a method for fabricating the same are disclosed. A thin film transistor substrate includes a substrate comprising a plurality of grooves having different depths, respectively, to have a multi-step structure; gate and data lines alternatively crossed in the grooves to form a plurality of pixel areas; thin film transistors formed in the grooves of the substrate to be formed in cross portion of the gate and data lines, wherein active layers of the thin transistors are formed along the gate lines and gate electrodes, the active layers separated from active layers of neighboring pixel areas with the data line located there between.