FFS LCD Array Substrate Fabrication via Reduced Mask Processes
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Solution Overview
Problem
The fringe field switching mode liquid crystal display (FFS) array substrate manufacturing process requires numerous mask processes, leading to increased production costs and time due to the complexity of forming various layers and electrodes, which hampers efficiency and scalability.
Innovation Solution
A method involving the formation of a thin film transistor, passivation layers, and a pixel electrode using a reduced number of mask processes, including the use of photoresist patterns and dry etching to create undercut shapes, allowing for the efficient fabrication of an array substrate with fewer steps, such as 8 mask processes when using a polysilicon semiconductor layer or 6 when using amorphous silicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If numerous mask processes are used to form various layers and electrodes in FFS mode LCD, then the manufacturing precision and structural complexity are improved, but the production time and cost increase significantly
Solution Approach 1:
The patent combines multiple mask processes into fewer integrated processes. Specifically, it forms the common electrode and pixel electrode in the same process step, and creates multiple insulating patterns simultaneously using a single photoresist layer. This merging of operations reduces the total number of mask processes from the conventional multiple steps to just 6 mask processes, significantly reducing production time while maintaining manufacturing precision
Solution Approach 2:
The patent employs multi-functional photoresist patterns that serve multiple purposes. A single photoresist layer is used to form both the common electrode and pixel electrode patterns, and also to define multiple insulating patterns (first, second, and third insulating patterns) in different regions. This universal approach allows one photoresist processing step to accomplish what traditionally required multiple separate mask processes
2Device complexity
If numerous mask processes are used to form various layers and electrodes in FFS mode LCD, then the structural complexity and functionality are improved, but the manufacturing cost increases
Solution Approach 1:
The patent merges the formation of multiple electrodes and insulating patterns into consolidated process steps. By forming the common electrode and pixel electrode simultaneously, and creating multiple insulating patterns in the same photoresist processing step, the total number of mask processes is reduced to 6. This consolidation maintains the necessary structural complexity for FFS mode operation while significantly reducing manufacturing cost through fewer process steps and less material consumption
3Productivity
If a reduced number of mask processes is used, then the production time and cost are reduced, but the complexity of forming precise patterns and structures becomes more difficult
Solution Approach 1:
The patent applies local quality by creating photoresist patterns with different thicknesses in different regions. The first photoresist pattern has a first thickness in the first region, while the second photoresist pattern has a second thickness in the second region. This localized variation in photoresist thickness allows precise control over the etching depth and pattern formation in different areas, maintaining manufacturing precision even with reduced mask processes
Solution Approach 2:
The patent performs preliminary actions by forming photoresist patterns with predetermined thickness variations before the actual electrode and insulating pattern formation. The different thicknesses of photoresist patterns are established in advance to guide the subsequent etching processes, ensuring that the final patterns achieve the required precision without requiring additional corrective mask 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 mask processes, thereby decreasing production costs and time, enhancing manufacturing efficiency and enabling the production of FFS mode LCDs with improved efficiency and cost-effectiveness.
Implementation Method 1
forming first and second photoresist patterns on the auxiliary insulating layer and having second and third thicknesses, respectively, the second thickness greater than the third thickness; etching the auxiliary insulating layer, the second passivation layer and the first passivation layer using the first and second photoresist patterns as an etching mask
Implementation Method 2
performing a dry etching to remove the auxiliary insulating layer not covered by the first photoresist pattern and expose the first passivation layer and to form an insulating pattern below the first photoresist pattern, the insulating pattern and the first photoresist pattern forming an undercut shape
Implementation Method 3
performing a lift-off process to remove the first photoresist pattern and the transparent conductive material layer thereon together and form a pixel electrode as a remaining portion of the transparent conductive material layer
Data Source
AI summary
A method of manufacturing an array substrate for a fringe field switching mode liquid crystal display includes: forming an auxiliary insulating layer having a first thickness; forming first and second photoresist patterns on the auxiliary insulating layer; performing an ashing to remove the second photoresist pattern and expose the auxiliary insulating layer therebelow; performing a dry etching to remove the auxiliary insulating layer not covered by the first photoresist pattern and expose a first passivation layer and to form an insulating pattern below the first photoresist pattern, the insulating pattern and the first photoresist pattern forming an undercut shape; forming a transparent conductive material layer having a fourth thickness less than the first thickness; and performing a lift-off process to remove the first photoresist pattern and the transparent conductive material layer thereon together and form a pixel electrode.