Stacked Display Substrates for Yield-Friendly Transistor Optimization
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Solution Overview
Problem
The existing process of forming transistors for display devices using organic electroluminescence is complicated and results in low yield, especially when trying to reduce substrate size, as the required characteristics of transistors for light-emitting parts and peripheral circuits are mismatched.
Innovation Solution
A display device is manufactured by stacking a first substrate with a semiconductor material layer forming the transistor and a second substrate with a predetermined circuit, with a pad opening exposed on the bottom surface, allowing for separate optimization of transistor processes for each substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transistors for light-emitting parts and peripheral circuits are formed on the same substrate in a common semiconductor element manufacturing process, then integration is achieved, but the process becomes very complicated and yield decreases
Solution Approach 1:
The patent divides the substrate into a first substrate for forming transistors that drive light-emitting parts and a second substrate for forming transistors in peripheral circuits. This segmentation allows each substrate to be optimized independently for its specific function, avoiding the need for a single complex manufacturing process while maintaining high yield through specialized processing for each region.
2Device complexity
If transistors for light-emitting parts and peripheral circuits are formed on the same substrate, then integration is achieved, but it becomes difficult to cope with reduction in size such as substrate size
Solution Approach 1:
By segmenting the substrate into first and second substrates with distinct functional regions, the patent enables independent optimization of each area. This allows the overall device to be miniaturized more effectively since each substrate can be sized and configured specifically for its intended function, rather than accommodating all functions in a single larger substrate.
Solution Approach 2:
The patent forms a light-emitting part on the first substrate and connects it to a peripheral circuit on the second substrate through vertical connections (pad openings and pad electrodes). This three-dimensional arrangement allows integration of multiple functions in a compact footprint by utilizing the vertical dimension for inter-substrate connections, thereby reducing the overall substrate area required.
3Ease of manufacture
If required characteristics of transistors for light-emitting parts and peripheral circuits are matched on the same substrate, then uniform manufacturing is simplified, but the required characteristics do not always match making this approach problematic
Solution Approach 1:
The patent applies different manufacturing optimizations to different regions: the first substrate is optimized for transistors driving light-emitting parts with specific characteristic requirements, while the second substrate is optimized for peripheral circuit transistors with different requirements. This local quality approach allows each region to have the precise characteristics needed for its function without compromising the other, achieving both manufacturing feasibility and characteristic matching.
Data Source
AI summary
A display device includes: a first substrate that includes a semiconductor material layer in which a transistor has been formed, the transistor driving a light-emitting part that is included in a pixel; and a second substrate that includes a predetermined circuit. The first substrate and the second substrate are stuck together in such a way that respective joint surfaces face each other. A pad opening is provided from a side of the first substrate to face a pad electrode that has been provided on a side of the respective joint surfaces, in such a way that the pad electrode is exposed on a bottom surface.