Thin Film Patterning via Two-Step Exposing Process
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Solution Overview
Problem
In high-resolution TFT-LCD manufacturing, reducing the line width of thin film layer patterns is challenging due to the limitations of mask size, leading to underexposure and defects such as poor slope formation, which affects product quality.
Innovation Solution
A method involving a two-step exposing process with a mask, where a first partially cured zone is formed with energy below the photosensitive threshold, followed by a second exposing process to create a cured zone with a width less than the first, ensuring full curing and allowing for precise line width reduction without decreasing the mask opening area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the mask opening area is decreased to reduce line width, then the line width of thin film layer patterns is reduced, but underexposure occurs leading to poor slope formation and defects
Solution Approach 1:
The exposing process is segmented into two distinct stages: a first exposing process that forms a partially cured zone with broader exposure, and a second exposing process that forms a cured zone with narrower width. This segmentation allows the mask opening area to remain large (avoiding underexposure) while the final pattern achieves reduced line width through the combination of both exposing steps.
Solution Approach 2:
The first exposing process performs a preliminary action by forming a partially cured zone that prepares the photoresist for the subsequent second exposing process. This preliminary exposure creates a foundation that enables the second exposing to achieve precise line width reduction without requiring a small mask opening, thereby preventing underexposure defects.
2Reliability
If the mask opening area is maintained large, then underexposure is avoided and good slope formation is achieved, but the line width of patterns cannot be reduced
Solution Approach 1:
The solution transitions from a single-dimension approach (controlling line width through mask opening size) to a two-dimension approach by introducing both spatial dimension (mask opening area) and process dimension (two-step exposing with different energy levels). This allows the mask to maintain large opening area for reliable exposure while the dual exposing process achieves fine line width control through energy accumulation and differential curing.
3Device complexity
If a single exposing process is used, then the process is simple, but the line width cannot be precisely controlled below mask aperture dimension
Solution Approach 1:
The patent applies parameter changes by varying the exposing energy parameters between two exposing processes. The first exposing uses parameters that create partial curing with a certain width, while the second exposing uses different parameters (same mask but controlled exposure) to achieve narrower cured zone. This parameter differentiation enables precise line width control below the mask aperture dimension while maintaining process feasibility.
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 method effectively decreases the line width of thin film layer patterns, enhancing resolution and product quality by avoiding underexposure-related defects while maintaining the mask size, thus improving the precision and reliability of pattern formation.
Implementation Method 1
forming a cured zone on the first partially cured zone by performing a second exposing process of the photoresist with the mask, wherein the cured zone has a width less than that of the first partially cured zone, exposing energy applied to the photoresist of the cured zone is greater than a photosensitive threshold of the photoresist
Data Source
Figure 1~2a
Figure 2b~2d
Figure 2e~3a
AI summary
A method of patterning a thin film is provided. The method includes coating a thin film layer (100) and photoresist (101) on a surface of a substrate; forming a first partially cured zone (201) by performing a first exposing process of the photoresist with a mask (20), wherein exposing energy applied to the photoresist (101) of the first partially cured zone (201) is less than a photosensitive threshold E of the photoresist; forming a cured zone (202) on the first partially cured zone (201) by performing a second exposing process of the photoresist (101) with the mask (20), wherein a width L2 of the cured zone (202) is less than a width L1 of the first partially cured zone (201), and exposing energy applied to the photoresist (101) of the cured zone (202) is equal to or greater than the photosensitive threshold E of the photoresist (101); developing the photoresist (101); etching the thin film layer (100) that is not covered by the photoresist (101); and removing the photoresist (101) of the cured zone (202).