Array Substrate Lithography Using Multi-Tone Photomasks
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Solution Overview
Problem
Conventional lift-off processes in liquid crystal display manufacturing require multiple photomasks and can lead to defects and obstruction issues in mass production due to the stripping of photoresist layers.
Innovation Solution
A method using multi-tone photomasks to pattern photoresist layers, allowing for selective deposition of insulation, semiconductor, and passivation layers without the lift-off process, reducing the number of photomasks needed and preventing material adherence or pipe obstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the conventional lift-off process is used to reduce the number of photomasks, then the number of photomasks is reduced, but the stripped coating film adheres to the substrate forming defects or suspends in the stripper to obstruct stripper pipes
Solution Approach 1:
The patent introduces an organic solvent-resistant coating layer as an intermediary between the inorganic coating layer and the photoresist layer. This intermediary layer allows the photoresist to be removed by organic solvents without damaging the inorganic coating, thereby eliminating the harmful effects of conventional lift-off processes while maintaining the simplified single photomask approach.
Solution Approach 2:
The patent changes the chemical resistance parameters of the coating structure by forming an organic solvent-resistant coating layer that specifically resists organic solvents used in photoresist removal. This parameter change enables selective removal of photoresist without affecting the underlying inorganic coating layers, resolving the contradiction between simplified process and production reliability.
2Manufacturing precision
If four or five lithography steps are used to manufacture array substrate, then the manufacturing precision is improved, but the productivity is reduced due to increased process complexity
Solution Approach 1:
The patent merges multiple lithography steps into a single lithography process by using a photoresist layer that can define multiple patterns simultaneously. The organic solvent-resistant coating layer enables this consolidation by allowing complete photoresist removal after single-step patterning, thereby improving productivity without sacrificing manufacturing precision.
Solution Approach 2:
The patent performs preliminary formation of the organic solvent-resistant coating layer before the lithography step. This preliminary action enables subsequent single-step lithography to achieve results that would otherwise require multiple steps, as the resistant coating layer is already in place to protect the inorganic coating during the simplified process.
3Device complexity
If the photoresist layer is used as a sacrificing layer in lift-off process, then the number of photomasks is reduced, but the coating film on photoresist layer cannot be removed without forming defects
Solution Approach 1:
The organic solvent-resistant coating layer serves as a mediator that differentiates between organic and inorganic materials. It allows organic photoresist to be removed by organic solvents while protecting the inorganic coating layer, making the removal process easy and defect-free while maintaining the single photomask benefit.
Solution Approach 2:
The patent applies local quality differentiation by creating a coating structure where the organic solvent-resistant layer has specific chemical resistance properties that differ from the inorganic coating layer. This local quality difference enables selective removal of photoresist without affecting the inorganic coating, resolving the manufacturing difficulty.
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 manufacturing process, reduces defects, and enhances production efficiency by eliminating lift-off issues, enabling mass production without the need for additional photomasks and improving the quality of array substrates.
Implementation Method 1
patterning the first photoresist layer by a lithography process with a first multi-tone photomask
Implementation Method 2
ashing the first thin photoresist pattern to expose the gate electrode, the gate line, the common line, and the wiring region of the bottom electrode
Implementation Method 3
selectively depositing an insulation layer on the substrate, the gate electrode, the gate line, the common line, and the wiring region of the bottom conductive line
Data Source
AI summary
Disclosed is a method of forming array substrates having a peripheral wiring area and a display area. The method is processed by only three lithography processes with two multi-tone photomasks and one general photomask. In the peripheral wiring area, the top conductive line directly contacts the bottom conductive line without any other conductive layer. The conventional lift-off process is eliminated, thereby preventing a material (not dissolved by a stripper) from suspending in the stripper or remaining on the array substrate surface.