Large Glass Substrate Arcuate Shaping for Exposure Flatness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Large-size glass substrates used in TFT liquid crystal panels face challenges in achieving high flatness when held horizontally in exposure apparatuses, leading to increased proximity gaps and reduced exposure accuracy, as existing methods struggle to control the necessary forces and correct for substrate deflection due to size and weight, especially for substrates larger than 500 mm in diagonal length.
Innovation Solution
A method for preparing large-size glass substrates involves calculating and removing specific quantities of material based on vertical attitude flatness and parallelism measurements, deflection correction, substrate support deformation, platen accuracy distortion, and polishing changes to achieve an arcuate shape that reduces proximity gaps when held horizontally, using techniques like sandblasting with cerium oxide or silicon carbide particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the size of glass substrates is increased to meet higher definition panel requirements, then the exposure range and productivity are improved, but the substrate deflection due to weight increases, leading to reduced flatness and exposure accuracy
Solution Approach 1:
The patent applies preliminary action by pre-correcting the substrate shape before exposure. The substrate is intentionally shaped with an arcuate profile that anticipates and compensates for the deflection that will occur when the substrate is held horizontally during exposure. This preliminary shaping ensures that when the substrate sags under its own weight, the pre-corrected shape results in the desired flat exposure surface.
Solution Approach 2:
The patent changes the geometric parameters of the substrate by introducing a controlled arcuate shape with specific radius of curvature. By adjusting the radius of curvature based on substrate size, thickness, and material properties, the patent optimizes the balance between substrate strength (to reduce excessive deflection) and the pre-corrected shape (to ensure flatness during exposure).
2Strength
If the thickness of large-size glass substrates is increased to reduce deflection, then the structural strength is improved, but the weight increases, leading to greater deflection and reduced flatness
Solution Approach 1:
The patent optimizes the thickness parameter to achieve the minimum required structural strength while avoiding excessive weight. By carefully selecting the thickness parameter and combining it with the arcuate shape correction, the patent achieves a balance where the substrate has sufficient strength to maintain its shape but not so thick that its weight causes excessive deflection during horizontal holding.
Solution Approach 2:
The patent applies curvature to the substrate surface in the form of an arcuate profile with a controlled radius of curvature. This curvature serves two functions: it strengthens the substrate structure by distributing stresses more evenly, and it provides the pre-correction needed to compensate for gravitational deflection during horizontal exposure.
3Ease of manufacture
If conventional polishing methods are used on large-size substrates, then the manufacturing process is simple, but the ability to remove moderate irregularities decreases, failing to achieve desired flatness
Solution Approach 1:
The patent applies preliminary shaping through arcuate profile correction before the final polishing stage. By pre-correcting the major shape deviations and deflection patterns, the subsequent polishing process only needs to remove minor irregularities, making the polishing process more effective and easier to control while achieving the desired flatness.
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 significantly reduces proximity gap variations between the photomask and mother glass substrates, improving exposure accuracy and enabling high-definition panel exposure with reduced correction burdens on the exposure apparatus, enhancing production yield and efficiency.
Implementation Method 1
processing for flattening and deformation-correction by removing a total quantity of material derived from a flattening removal quantity and a deformation-corrective removal quantity
Data Source
Figure 1~2
Figure 3~4
AI summary
A large-size glass substrate, from which a photomask substrate is formed, is prepared by processing a large-size glass substrate stock by (1) a flattening removal quantity based on height data of the substrate stock in the vertical attitude plus a deformation-corrective removal quantity. The deformation-corrective removal quantity is calculated from (2) a deflection of the substrate stock by its own weight in the horizontal attitude, (3) a deformation of the photomask substrate caused by chucking in an exposure apparatus, and (4) an accuracy distortion of a platen for supporting a mother glass.