TFT-LCD Pixel Unit Gray Tone Mask Process
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Solution Overview
Problem
Conventional TFT-LCD manufacturing processes require strict process tolerance and multiple masks, leading to increased costs, machine occupation time, and reduced yield.
Innovation Solution
A three-mask photolithography process is used to form a TFT-LCD pixel unit, involving a gate line, gate electrode, active layer, doped layer, and insulating layers, with a lift-off process to reduce process complexity and improve yield, while using gray tone masks to form intercepting trenches and source/drain electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a five-mask or four-mask method is used to fabricate TFT LCD, then the manufacturing precision and reliability are improved, but the device complexity, manufacturing cost, and machine occupation time increase
Solution Approach 1:
The patent merges the formation of intercepting trenches and source/drain electrodes into a single etching step using a gray tone mask. The gray tone mask enables simultaneous patterning of multiple features (intercepting trenches and source/drain electrodes) that were previously formed in separate steps, thereby reducing the total mask count from four or five to three masks while maintaining etching precision.
Solution Approach 2:
The gray tone mask serves multiple functions: it defines both the intercepting trenches and the source/drain electrodes in a single exposure step. This multi-functional approach eliminates the need for separate masks for each feature, reducing process complexity while achieving the required manufacturing precision for both features.
2Manufacturing precision
If a four-mask method with gray tone mask is used, then the manufacturing precision is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the formation of intercepting trenches and source/drain electrodes into a single etching step using the gray tone mask. This merging of operations maintains the etching uniformity and precision achieved by the gray tone method while simplifying the overall process by eliminating one mask step and reducing the total number of process steps.
3Manufacturing precision
If strict process tolerance is maintained in conventional four-mask method, then the manufacturing precision is improved, but the productivity decreases
Solution Approach 1:
By merging the formation of intercepting trenches and source/drain electrodes into a single etching step with the gray tone mask, the patent reduces the number of process steps and associated variability. This consolidation maintains precise process control while reducing cumulative errors from multiple steps, thereby improving yield and productivity.
4Manufacturing precision
If a five-mask or four-mask method is used, then the manufacturing precision is improved, but the machine occupation time increases
Solution Approach 1:
The patent merges multiple patterning operations into a single mask step using the gray tone mask. This eliminates the need for separate mask alignment and etching steps for intercepting trenches and source/drain electrodes, significantly reducing machine occupation time while maintaining the precision required for pattern formation.
Solution Approach 2:
The gray tone mask is designed and prepared in advance to simultaneously define both intercepting trenches and source/drain electrodes. This preliminary preparation of a multi-functional mask allows both features to be formed in a single exposure and etching step, reducing the total number of machine operations required.
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
The three-mask process reduces manufacturing costs, shortens machine occupation time, and increases yield by simplifying the design and improving process tolerance, while avoiding contact resistance issues with transparent metal electrodes.
Implementation Method 1
a coated photoresist layer is exposed with the first gray tone mask and developed to obtain a first photoresist pattern
Implementation Method 2
An ashing process is performed to partially remove the photoresist pattern and thus expose the channel portion
Data Source
AI summary
A thin film transistor liquid crystal display (TFT-LCD) pixel unit and a method for manufacturing the same. The pixel unit comprises a gate line and a gate electrode formed on a substrate and a first gate insulating layer, an active layer, and a doped layer sequentially that are formed on the gate line and the gate electrode. An intercepting trench is formed on the gate line to cut off the doped layer and the active layer on the gate line. A second insulating layer covers the intercepting trench and the substrate where the gate line and the gate electrode are not formed. A pixel electrode is formed on the second insulating layer and is integrated with the second source/drain electrode.