TFT-LCD Array Substrate Using Three Masks
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Solution Overview
Problem
Conventional TFT-LCD array substrate manufacturing methods require strict process tolerance and multiple masks, increasing complexity and cost.
Innovation Solution
A TFT-LCD array substrate manufacturing method using three masks, including a second insulating layer to expose the channel, source, and drain regions of the TFT, simplifying the design and reducing process requirements through a gray tone mask and photoresist lifting-off process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional 4Mask technology is used to etch source/drain metal layer and active layer in the channel region, then the TFT structure can be formed, but the process tolerance requirements become strict and the manufacturing complexity increases
Solution Approach 1:
The invention segments the etching process into two distinct stages: first etching the metal layer to form openings, then etching the active layer through the same openings. This segmentation allows each etching step to be optimized independently, reducing the cumulative tolerance requirements compared to simultaneous multi-layer etching in conventional 4Mask technology
Solution Approach 2:
The metal layer is etched in advance to create openings before etching the active layer. This preliminary action establishes precise etching windows that guide the subsequent active layer etching, ensuring accurate alignment and reducing the stringency of tolerance requirements for the overall process
2Manufacturing precision
If gray tone mask and ashing process are used to expose the channel region, then the source/drain metal layer can be etched, but the photoresist control requirements become strict
Solution Approach 1:
The photoresist processing is segmented into two functional types: a gray tone mask for the first etching step and a standard photoresist for the second etching step. This segmentation allows each photoresist to be optimized for its specific function, reducing the overall stringency of control requirements
Solution Approach 2:
The metal layer serves as an intermediary structure that is etched first to create openings. This intermediary step simplifies the subsequent photoresist requirements by providing pre-formed etching windows, reducing the complexity of photoresist pattern control
3Reliability
If multiple etching steps are performed on metal layer, doped layer, and active layer, then the TFT channel region can be properly formed, but the process tolerance requirements increase
Solution Approach 1:
The multi-layer etching process is segmented into two independent stages: metal layer etching followed by active layer etching. Each stage can be optimized with appropriate photoresist and etching parameters, reducing the cumulative tolerance requirements compared to simultaneous multi-layer etching while maintaining TFT structure reliability
Solution Approach 2:
The metal layer is etched in advance to create precise openings that serve as templates for the subsequent active layer etching. This preliminary action ensures accurate alignment and reduces the stringency of tolerance requirements for the overall multi-layer etching process
4Reliability
If conventional 5Mask or 4Mask technology is used, then complete TFT fabrication can be achieved, but the manufacturing cost and time increase
Solution Approach 1:
The invention merges the functions of multiple masks into a simplified two-mask process: a gray tone mask for the first etching step and a standard photoresist for the second etching step. This merging reduces the total number of masking operations while maintaining complete TFT fabrication capability, thereby improving manufacturing efficiency
Solution Approach 2:
The metal layer is etched in advance to create openings before the active layer is etched. This preliminary action simplifies the overall process by establishing etching windows early, reducing the need for additional masking steps and improving manufacturing efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method reduces manufacturing costs and time, improves productivity, and simplifies the design of the TFT-LCD array substrate by completing the substrate with just three masks, enhancing feasibility and equipment usage.
Implementation Method 1
an ashing process is performed on the photoresist layer to expose the channel region of the TFT
Implementation Method 2
the source/drain metal layer in the channel region is etched, and thereafter the doped layer and the active layer in the channel region are etched
Data Source
AI summary
A pixel unit of TFT-LCD array substrate and a manufacturing method thereof is disclosed. In the manufacturing method, besides a first insulating layer and a passivation layer, a second insulating layer is adopted to cover the gate island, and forms an opening on the gate island to expose the channel region, the source region and the drain region of the TFT. A gray tone mask and a photoresist lifting-off process are utilized to perform patterning, so that the TFT-LCD array substrate can be achieved with just three masks.