Back Exposure LCD Fabrication via Conductive Mask
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Solution Overview
Problem
The existing methods for fabricating large area electronic devices, such as LCDs, require complex and costly photolithography processes, including the use of photolithographic masks, which increases production costs and complexity, especially when forming patterned structures and passivation layers.
Innovation Solution
A method that forms patterned structures and passivation layers for LCDs using a self-aligned back exposure technique, eliminating the need for photolithographic masks by using a patterned conductive layer as a mask for the back exposure process, and a reflowed photoresist passivation layer to cover the TFT and capacitor, reducing the number of photolithography steps to four.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional photolithography process is used to form patterned structures and passivation layers, then manufacturing precision can be maintained, but device complexity and production cost increase due to multiple photolithography steps and mask requirements
Solution Approach 1:
The patterned conductive layer serves as its own mask for the back exposure process, eliminating the need for separate photolithographic masks. The conductive layer's inherent pattern automatically defines the exposure areas, making the system self-sufficient and reducing external tooling requirements
Solution Approach 2:
Instead of performing photolithography from the front of the substrate, the patent uses back exposure through the transparent substrate. This inverted approach allows the patterned conductive layer to function as a mask without requiring traditional photolithographic mask alignment, simplifying the overall process
2Productivity
If photolithographic masks are used for patterning, then manufacturing precision is maintained, but production cost and time increase due to mask production and alignment requirements
Solution Approach 1:
The patterned conductive layer automatically serves as the exposure mask, eliminating the time-consuming mask production and alignment steps. The system uses its own structural features to define the patterning areas, removing the need for separate masking operations
Solution Approach 2:
The patent extracts and eliminates the photolithographic mask step from the fabrication process entirely. By using the conductive layer's inherent pattern and back exposure, the time-consuming mask production and alignment operations are completely removed from the production flow
3Manufacturing precision
If conventional lift-off process is used to create patterned metal layers, then manufacturing precision is improved by eliminating etch processes, but production cost increases due to photolithography requirements
Solution Approach 1:
Instead of using front-side photolithography with lift-off, the patent inverts the approach by using back exposure through the transparent substrate. The patterned conductive layer acts as the mask from the back side, maintaining patterning precision while eliminating the need for traditional photolithographic masks and their associated costs
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 simplifies the fabrication process, reduces production costs, minimizes alignment errors, and increases throughput by eliminating the need for photolithographic masks and reducing the complexity of the fabrication process while effectively forming patterned structures and passivation layers.
Implementation Method 1
exposure process technique so-called 'back exposure' has been proposed to form desired transparent, colored and fine patterns on a transparent substrate by exposure to light from the back of the substrate with an opaque pattern as photo-mask
Implementation Method 2
The photoresist passivation layer is subjected to a middle bake process to be reflowed, resulting in a complete covering of the patterned opaque conductive layer
Data Source
AI summary
A method for fabricating a pixel structure of a liquid crystal device is provided. The method comprises providing a substrate defining a thin film transistor (TFT) region and a display region thereon. An opaque conductive layer is formed on the TFT region, and a transparent pixel electrode is formed on the display region. A patterned photoresist passivation layer is formed by backside exposure process on the TFT region, wherein the opaque conductive layer serves as the photo-mask during the backside exposure process. The photoresist passivation layer is subjected to a middle bake process to be reflowed, resulting in a complete covering of the opaque conductive layer.