Segmented Contact Holes for LCD Pixel Electrode Connections
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Solution Overview
Problem
Conventional methods for producing liquid crystal display devices using poly-silicon switching elements result in incomplete dissolution of photoresist in contact holes, leading to increased electric resistance and poor connections between drain and pixel electrodes.
Innovation Solution
The method involves forming a first organic insulating film covering signal lines and switching elements, creating first contact holes, forming connection elements through these holes, covering with a second organic insulating film, and forming second contact holes for pixel electrodes, ensuring complete connection without residue and maintaining low resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a second contact hole is formed to connect the drain electrode to the pixel electrode through two layers of organic insulating films, then the connection path is established, but the photoresist film remains undissolved in the contact hole causing increased electric resistance and poor connection
Solution Approach 1:
The patent divides the contact hole formation process into two separate steps: first forming a contact hole through the first organic insulating film to reach the drain electrode, then forming a second contact hole through the second organic insulating film to reach the pixel electrode. This segmentation allows each photoresist layer to be completely removed at its respective contact hole location, preventing residue accumulation and ensuring clean electrical connections.
Solution Approach 2:
The patent performs preliminary patterning and contact hole formation in the first organic insulating film before forming the second organic insulating film. This preliminary action ensures that the first contact hole is completely cleared of photoresist before the second layer is applied, preventing future connection issues.
2Reliability
If the contact hole depth increases to pass through multiple insulating film layers, then the electrical connection path is established, but photoresist residue remains causing increased electric resistance
Solution Approach 1:
The patent segments the deep contact path into two shallower contact holes formed at different stages. The first contact hole penetrates only the first organic insulating film, and the second contact hole penetrates only the second organic insulating film. This segmentation ensures that photoresist is completely removed at each stage, eliminating residue that would otherwise accumulate in a single deep contact hole.
3Ease of manufacture
If photoresist is not completely dissolved in the contact hole, then the manufacturing process is simplified, but electric resistance increases and connection quality deteriorates
Solution Approach 1:
The patent applies segmentation to the photoresist removal process by forming contact holes in separate stages. Each photoresist layer is removed completely at its corresponding contact hole location, ensuring high contact hole quality without requiring complex multi-step etching or cleaning processes.
Data Source
AI summary
A liquid crystal display device having a plurality of pixels arranged in a matrix includes first and second substrates and a liquid crystal layer held therebetween. Switching elements are arranged in each of the pixels on the first substrate. A first organic insulating film covers signal lines, scan lines and switching elements. Common electrodes are formed in the first organic insulating film on the first substrate. Connection elements are electrically connected to the switching elements through first contact holes formed in the first organic insulating film. A second organic insulating film covers the first organic insulating film and the connection elements. Pixel electrodes having slits are formed on the second organic insulating film electrically connected to the respective connection elements through second contact holes formed in the second organic insulating film. The liquid crystal layer is switched by using a lateral electric field between the common and pixel electrodes formed on the first substrate.