Large Glass Substrate Flatness via Pre-Deformation Correction

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 gap variations and reduced exposure accuracy, as existing methods struggle to control the necessary forces and measure flatness accurately in the horizontal attitude.

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 data, deflection due to substrate weight, deformation caused by support, accuracy distortions of the platen, and changes during polishing, resulting in an arcuate shape that reduces proximity gap variations when held horizontally.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the substrate size is increased to enable multiple pattern panelization through single exposure, then productivity is improved, but the substrate becomes deflected on horizontal holding, leading to reduced flatness

Engineering Contradiction:

Improvemultiple pattern panelization throughputVSAvoidflatness when held horizontally

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary deformation correction to the glass substrate before exposure. By pre-flattening the substrate and correcting its deformation characteristics in advance, the substrate maintains high flatness when held horizontally during exposure, enabling both large size for productivity and precision for accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the physical parameters of the glass substrate, specifically its thickness and deformation characteristics. By optimizing substrate thickness and applying pre-flattening processing, the substrate achieves both large dimensions for multiple pattern panelization and sufficient flatness when held horizontally during exposure.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If the substrate thickness is increased to reduce deflection by weight, then flatness is improved, but the weight of the substrate increases

Engineering Contradiction:

Improveflatness when held horizontallyVSAvoidsubstrate weight

Core Design Contradiction:

Manufacturing precisionVSWeight of moving object

Solution Approach 1:

The patent applies preliminary deformation correction to the glass substrate before exposure. By pre-flattening the substrate and correcting its deformation characteristics in advance, the substrate maintains high flatness when held horizontally during exposure, enabling both large size for productivity and precision for accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the physical parameters of the glass substrate, specifically its thickness and deformation characteristics. By optimizing substrate thickness and applying pre-flattening processing, the substrate achieves both large dimensions for multiple pattern panelization and sufficient flatness when held horizontally during exposure.

Inventive Principle:

Principle #35Parameter changes

3Area of stationary object

If the substrate size is increased, then the area for multiple pattern exposure is improved, but the reaction force for flatness correction decreases

Engineering Contradiction:

Improvesubstrate area for exposureVSAvoidflatness correction ability

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent applies preliminary deformation correction to the glass substrate before exposure. By pre-flattening the substrate and correcting its deformation characteristics in advance, the substrate maintains high flatness when held horizontally during exposure, enabling both large size for productivity and precision for accuracy.

Inventive Principle:

Principle #10Preliminary action

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 improves exposure accuracy and reduces the burden of correction on the exposure apparatus, enabling the production of high-definition large-size panels with increased yield and efficient exposure processes.

Implementation Method 1

processing a large-size glass substrate stock having front and back surfaces and a diagonal length of at least 500 mm and a thickness of at least 4 mm into the large-size glass substrate by removing therefrom (1) a flattening removal quantity of material based on height data of the flatness and parallelism of the front and back surfaces of the large-size glass substrate stock in the vertical attitude, plus a deformation-corrective removal quantity of material

Methodology Applied

Scientific EffectAbrasion: Abrasion

Implementation Method 2

the deflection of a substrate by its own weight is in inverse proportion to the cube of its thickness, the size enlargement has a propensity that as the size of a substrate is increased, its thickness is also increased

Methodology Applied

Scientific EffectGravitational deflection: Gravitation

Implementation Method 3

a reaction force against the elastic deformation generated when the substrate itself is forced against the processing platen

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS7608542B2Large-size glass substrate for photomask and making method, computer-readable recording medium, and mother glass exposure method

Publication Date: 2009.10.27 SHIN ETSU CHEMICAL CO LTD

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.