Transflective LCD Array Substrate Pad Contact
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Solution Overview
Problem
The existing fabrication method for transflective liquid crystal display devices is complex and expensive due to the difficulty in forming a half photoresist (PR) layer in the pad region, which can lead to weak or incomplete contact between the gate pad and the indium-tin-oxide (ITO) layer, resulting in ineffective device performance.
Innovation Solution
A method involving a four mask process is developed to form an array substrate for transflective liquid crystal display devices, where a gate pad is formed on a substrate with a gate insulator and an auxiliary pad pattern made of intrinsic amorphous silicon, and a conductive layer is deposited to contact the gate pad through an opening, reducing the thickness of the passivation layer and creating a low step for easier half PR formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick passivation layer is formed in the pad region, then the gate pad is well protected, but the step height increases making half PR formation difficult and contact between gate pad and ITO layer weak or incomplete
Solution Approach 1:
The passivation layer is segmented into different thickness regions: a first passivation layer with greater thickness for protection, and a second passivation layer with lesser thickness to reduce step height. This segmentation allows the pad region to have both protection and ease of half PR formation.
Solution Approach 2:
Different regions of the passivation layer have different thicknesses tailored to their specific functions. The pad region has reduced thickness locally to facilitate half PR formation and ensure good contact, while other regions maintain sufficient thickness for protection.
2Reliability
If a thick passivation layer is formed in the pad region, then the gate pad is well protected, but the fabrication process becomes more complex and expensive
Solution Approach 1:
The passivation layer is divided into two distinct layers with different thicknesses, allowing simplified fabrication processes while maintaining both protection and manufacturability. This segmentation avoids the need for complex single-layer thickness control.
3Ease of manufacture
If the passivation layer thickness is reduced in the pad region, then half PR formation becomes easier and contact is improved, but the gate pad protection is reduced
Solution Approach 1:
The passivation protection is segmented into two layers: the first layer provides primary protection with greater thickness, while the second layer provides additional protection with lesser thickness. This ensures adequate protection even when the overall passivation thickness is reduced in the pad region.
Solution Approach 2:
The first passivation layer is formed preliminarily to provide base protection before forming the second passivation layer. This preliminary protection ensures the gate pad is protected during subsequent processing steps.
Data Source
AI summary
An array substrate for a transflective liquid crystal display device and its fabrication method are discussed. In one embodiment, an array substrate for a transflective liquid crystal display device includes a gate pad on a base substrate, a gate insulator on the gate pad and having an opening exposing a portion of the gate pad, an auxiliary pad pattern on the gate insulator and made of an intrinsic amorphous silicon layer, and a conductive layer on the auxiliary pad pattern and contacting the gate pad through the opening.