Thin Film Transistor Substrate Reducing Masking Steps
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Solution Overview
Problem
The fabrication of thin film transistor substrates for liquid crystal display devices, particularly in the FFS mode, requires a high number of masking steps, leading to increased process costs and time.
Innovation Solution
A method and structure for a thin film transistor substrate that reduces the number of fabrication steps by forming the gate electrode, semiconductor pattern, source/drain electrodes, and common electrode using fewer masks, with a specific configuration of protective films and electrodes to create a fringe field, allowing for a pixel electrode to be formed with an undercut structure, thereby reducing duplicative mask steps and parasitic capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If seven masking steps are used to form gate electrode, semiconductor pattern, source/drain electrodes, and common electrode, then the thin film transistor substrate can be fabricated with proper electrode patterns, but the fabrication process cost and time increase significantly
Solution Approach 1:
The patent combines the formation of the common electrode and the pixel electrode into a single masking step. The transparent conductive layer is patterned to form both electrodes simultaneously, eliminating the need for separate masking processes. This merging of operations reduces the total number of masking steps from seven to fewer steps, directly addressing the contradiction between manufacturing precision and fabrication time.
Solution Approach 2:
The transparent conductive layer serves multiple functions: it forms both the common electrode and the pixel electrode, and it provides the fringe field necessary for FFS mode operation. By making this single layer perform multiple functions that previously required separate layers and processing steps, the patent reduces fabrication complexity while maintaining the required electrode patterns.
2Manufacturing precision
If seven masking steps are used for fabricating the thin film transistor substrate, then complete electrode patterns can be formed, but the process cost increases
Solution Approach 1:
The patent merges the common electrode and pixel electrode formation into one masking step, reducing the total number of masking operations. Since masking steps are among the most costly operations in semiconductor fabrication due to the expense of mask materials, alignment equipment, and processing time, this consolidation directly reduces manufacturing cost while maintaining the necessary electrode pattern precision.
3Manufacturing precision
If the common electrode and pixel electrode are formed in separate masking steps, then each electrode can be precisely patterned, but the number of fabrication steps increases to seven
Solution Approach 1:
The patent combines the patterning of the common electrode and pixel electrode into a single masking operation. The transparent conductive layer is patterned using one mask to define both electrodes simultaneously. This approach maintains manufacturing precision because the single masking step ensures proper alignment, while significantly improving productivity by reducing the total number of fabrication steps from seven to fewer steps.
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 approach reduces the number of fabrication steps from seven to five, lowers fabrication costs and time, and minimizes power consumption by reducing parasitic capacitors between the data lines and common electrode.
Implementation Method 1
a common electrode formed to form a fringe field with the pixel electrode
Data Source
AI summary
The present invention relates to methods for fabricating a thin film transistor substrate.