TFT Substrate Common Capacitor Stability via Selective CVD Layer Removal
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Solution Overview
Problem
The existing four-mask process for manufacturing TFT-LCD substrates results in varying capacitance when the polarities of the metal electrode plates change, leading to decreased video quality and reliability due to abnormalities such as afterimages and flickers.
Innovation Solution
A method involving the sequential formation of a first metal layer, a first chemical vapor deposition layer, and a second chemical vapor deposition layer on a substrate, where the first metal layer serves as a lower electrode of a common capacitor, and the chemical vapor deposition layers comprise silicon nitride, utilizing a halftone mask in the photolithography process to maintain capacitance and reduce the thickness of the isolation layer between electrode plates, allowing only silicon nitride to be sandwiched between the electrode plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the four-mask process is used to form the common capacitor with a complete CVD film sandwiched between metal electrode plates, then productivity is improved and production cost is reduced, but capacitance varies when positive and negative polarities of the metal electrode plates are changed, leading to video quality degradation and reliability issues
Solution Approach 1:
The invention extracts and removes the problematic amorphous silicon layer and ohmic contact layer from between the metal electrode plates of the common capacitor, leaving only the silicon nitride isolation layer. This is achieved by selectively etching the amorphous silicon layer and ohmic contact layer in the capacitor region while preserving the silicon nitride layer, thereby eliminating the source of capacitance variation and ensuring stable capacitance regardless of electrode polarity changes.
Solution Approach 2:
The invention applies different structural configurations to different regions of the substrate. In the common capacitor region, only the silicon nitride isolation layer is retained between the metal electrode plates, while in other regions, the complete CVD film structure (isolation layer, amorphous silicon layer, and ohmic contact layer) is preserved. This localized differentiation resolves the capacitance stability issue in the capacitor region while maintaining the functional integrity of other device regions.
2Ease of manufacture
If the complete CVD film is sandwiched between the signal line metal electrode and the metal gate electrode in the common capacitor, then the manufacturing process is simplified, but the capacitance varies with polarity changes causing afterimages and flickers
Solution Approach 1:
The invention converts the potentially harmful presence of the complete CVD film (which causes capacitance variation) into a beneficial selective structure. By selectively removing only the amorphous silicon layer and ohmic contact layer in the capacitor region while retaining the silicon nitride isolation layer, the invention eliminates the harmful capacitance variation effect while maintaining the simplicity of the CVD manufacturing process for other device regions.
3Stability of the object's composition
If the amorphous silicon layer, ohmic contact layer and isolation layer are all sandwiched between the metal electrode plates, then the capacitor structure is complete, but the capacitance varies when polarities change leading to video quality degradation
Solution Approach 1:
The invention segments the CVD film structure into functionally distinct layers and selectively removes specific layers from the common capacitor region. The silicon nitride isolation layer is retained to maintain structural integrity and electrical isolation, while the amorphous silicon layer and ohmic contact layer are removed to eliminate capacitance variation. This segmentation approach preserves the essential structural completeness while eliminating the harmful effects on video quality.
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 maintains capacitance stability, enhances video quality and reliability, and increases the aperture ratio of the display panel, reducing backlight power consumption while eliminating defects like flickers and afterimages.
Implementation Method 1
a first chemical vapor deposition layer and a second chemical vapor deposition layer respectively comprises a silicon nitride layer
Data Source
AI summary
The present invention provides a manufacture method of a thin film transistor substrate: forming a first metal layer, a first chemical vapor deposition layer, a second metal layer and a second chemical vapor deposition layer on a substrate; forming photoresistor on the second chemical vapor deposition layer; implementing exposure and development to the photoresistor; implementing via etching to a via area where the photoresistor on the second chemical vapor deposition layer is removed; implementing photoresistor ashing to remove the photoresistor in the area of the common capacitor; etching the silicon nitride layer; forming a pixel electrode layer. The present invention is capable of promoting video quality and saving the backlight power consumption.