Electro-Optical Device Connection Terminals with Overlapping Metal Layers
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Solution Overview
Problem
Existing electro-optical devices, such as liquid crystal displays, face challenges in achieving high electrical reliability and reduced size due to issues with the elevation difference between connection terminals connected to gate and source electrodes, leading to electrical shorts and increased resistance.
Innovation Solution
The electro-optical device features a substrate with display thin-film transistors and connection terminals where the first and second metal layers overlap in plan view, ensuring uniform elevation and eliminating the need for interconnects, allowing for reduced pitch and size while maintaining high electrical reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If interconnects are used to equalize the elevation of connection terminals, then the electrical connection reliability is improved, but the device size increases and the pitch between connection terminals must be reduced
Solution Approach 1:
The invention transitions from a planar arrangement of metal layers to a three-dimensional overlapping structure. The first metal layer is positioned at a different vertical level than the second metal layer, with the first insulating layer extending between them to create a stepped configuration. This vertical dimensionality allows connection terminals to achieve uniform elevation without requiring additional horizontal interconnect structures, thereby reducing device area while maintaining electrical connection reliability.
2Reliability
If interconnects are used to equalize the elevation of connection terminals, then the electrical connection reliability is improved, but additional wires are required increasing the complexity
Solution Approach 1:
The invention merges the functions of multiple metal layers and insulating layers into an integrated structure. The first metal layer, second metal layer, and first insulating layer are combined to simultaneously achieve elevation equalization and electrical connection, eliminating the need for separate interconnect wires. This merging of structural and functional elements reduces wiring complexity while improving electrical connection reliability.
3Reliability
If the pitch between connection terminals is reduced to accommodate interconnects, then the electrical connection reliability is improved, but the resistance of the liquid crystal display increases
Solution Approach 1:
By utilizing the vertical dimension with overlapping metal layers at different elevations, the invention allows connection terminals to be spaced farther apart horizontally without compromising electrical connection reliability. This reduced pitch requirement prevents increased wiring resistance and energy loss, as the overlapping three-dimensional structure provides robust electrical connections even with larger horizontal spacing between terminals.
Data Source
AI summary
An electro-optical device includes a substrate having a display region; TFTs each including a first electrode in the display region, a first insulating layer on the first electrode, a second electrode on the first insulating layer, and a second insulating layer on the second electrode; and terminals each including a first metal on a protruding section extending from the display region, which is located at the same level and made of the same metal as the first electrode, a second metal which is located at the same level and made of the same metal as the second electrode, and which partly overlaps the first metal in plan view, and a portion of the first insulating layer. The first insulating layer separates the first and second metals and the first metal is electrically connected to the first electrode or the second metal is electrically connected to the second electrode.