Thin Film Transistor Array Substrate Masking via Photoresist Topography
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Solution Overview
Problem
The manufacturing of thin film transistor array substrates is complicated and costly due to the need for multiple mask processes, with existing methods using five or four mask processes, and there is a desire to further reduce this number to simplify the process and lower costs.
Innovation Solution
A method that utilizes a lift-off process with an additional masking pattern formed without a mask process, using a photoresist pattern with uneven topography to pattern the conductive film, reducing the number of mask processes required in the manufacturing of thin film transistor array substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple mask processes are used to pattern the conductive film, then the manufacturing precision is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The photoresist pattern is formed in advance with predetermined uneven topography (thicker and thinner portions) before the conductive film deposition. This preliminary structuring of the photoresist layer serves as a built-in mask that eliminates the need for separate mask processes during conductive film patterning, thereby reducing process complexity while maintaining patterning precision.
Solution Approach 2:
The photoresist pattern itself serves dual functions: it acts as both the patterning mask and the topographic structure that defines the conductive film regions. The uneven topography of the photoresist automatically creates the necessary masking effect during conductive film formation, allowing the photoresist to 'serve itself' as the mask without requiring additional mask layers or processes.
2Manufacturing precision
If multiple mask processes are used, then the manufacturing precision is improved, but the loss of time increases
Solution Approach 1:
The functions of photoresist patterning and mask formation are merged into a single step. The photoresist is patterned once with uneven topography that simultaneously serves as both the pattern definition and the masking structure for the conductive film, eliminating the need for separate mask application and removal steps, thereby reducing processing time while maintaining precision.
Solution Approach 2:
The photoresist layer performs multiple functions: it defines the pattern geometry, creates the uneven topography, and serves as the masking structure for conductive film patterning. This multi-functionality eliminates the need for dedicated mask processes, reducing the overall processing time while maintaining the required patterning precision.
3Device complexity
If a lift-off process is used to pattern the conductive film, then the device complexity is reduced, but object-generated harmful factors increase due to contamination
Solution Approach 1:
Instead of using a lift-off process that causes contamination, the invention converts the photoresist's uneven topography into a beneficial masking structure. The thicker portions of the photoresist naturally serve as masks during conductive film deposition, eliminating the need for lift-off and preventing contamination while maintaining process simplicity.
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 contamination and equipment damage, decreases processing time, and lowers manufacturing costs by reducing the number of mask processes to three, while maintaining the quality and uniformity of the substrate.
Implementation Method 1
the photoresist can be formed on the passivation film and photolithographically patterned
Data Source
AI summary
In manufacturing a thin film transistor array substrate, a passivation film is formed over the transistors. A first photoresist pattern is formed over the passivation film, with a first portion partially overlying at least one source/drain electrode of each transistor and overlying each pixel electrode region, and with a second portion thicker than the first portion. The passivation film is patterned using the first photoresist pattern as a mask. The first photoresist pattern's first portion is removed to form a second photoresist pattern which protrudes upward around the pixel electrode regions. A transparent conductive film is formed with recesses in the pixel electrode regions. A masking pattern is formed over the transparent film in each pixel electrode region, the masking pattern's top surface being below a top of the transparent film. The transparent film is patterned using the masking pattern as a mask to form the pixel electrodes.