Mask Plate Redundant Pattern for Photoresist Uniformity
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Solution Overview
Problem
In the manufacturing of array substrates for horizontal electric field type TFT-LCDs, the double-tone mask plate leads to developer concentration differences across the photoresist regions, causing uneven photoresist thickness and morphology issues due to developer diffusion, which complicates subsequent etching processes and reduces product quality and yield.
Innovation Solution
A mask plate design with a first pattern region, a second pattern region having a different exposure level, and a redundant pattern between them to form a redundant photoresist pattern that prevents developer diffusion by maintaining concentration balance across the regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a double-tone mask plate is used to form patterns in photoresist, then cost is saved and the amount of mask processes is reduced, but developer concentration differences occur across photoresist regions causing uneven photoresist thickness and morphology issues
Solution Approach 1:
The patent introduces a redundant pattern region with specific optical properties (transmittance between 10-50%) between the first and second pattern regions. This creates locally different photoresist thickness profiles: the redundant pattern forms a protruding photoresist pattern that acts as a barrier, while adjacent regions maintain their intended thickness. This local structural differentiation prevents developer diffusion from high-concentration to low-concentration regions, resolving the thickness uniformity issue while maintaining the double-tone mask plate's process efficiency benefits.
2Loss of time
If developer concentration increases to remove photoresist faster, then development time is reduced, but photoresist thickness control in half-exposed regions becomes more difficult
Solution Approach 1:
The redundant pattern acts as an intermediary physical barrier between regions with different developer concentrations. The protruding photoresist pattern formed by the redundant pattern region blocks the direct diffusion path of developer molecules from high-concentration to low-concentration areas. This intermediary structure allows faster development with higher concentration developer while maintaining precise thickness control in half-exposed regions, as the barrier prevents excessive developer penetration.
3Productivity
If the thickness of remaining photoresist in half-exposed region is increased, then etching time is prolonged, but if thickness is decreased, peripheral morphology deteriorates and uncovered regions occur
Solution Approach 1:
The redundant pattern provides beforehand cushioning by creating a protruding photoresist barrier that protects adjacent half-exposed regions from developer diffusion. This pre-formed structural cushion maintains photoresist thickness and peripheral morphology integrity in regions that would otherwise be vulnerable to developer penetration. As a result, etching can proceed at optimal speeds without compromising the protective photoresist morphology, as the redundant pattern has already established the necessary structural buffer.
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
The redundant pattern ensures uniform photoresist thickness and morphology, reducing difficulties in etching and parameter control, thereby enhancing product quality and yield by preventing developer diffusion and maintaining concentration balance across the substrate regions.
Implementation Method 1
prevent developer diffusion at different concentrations across the photoresist redundant pattern
Implementation Method 2
exposing of photoresist (e.g., positive photoresist) with the mask plate, an exposed region is formed in the photoresist layer corresponding to the transparent region of the mask plate
Data Source
AI summary
An embodiment of the disclosed technology provides a mask plate for photolithography process comprising a first pattern region, a second pattern region having a different exposure level from that of the first pattern region, and a redundant pattern provided between the first pattern region and the second pattern region, wherein the redundant pattern is configured for forming a redundant photoresist pattern so as to prevent developer diffusion at different concentrations across the photoresist redundant pattern.