Photomask Segmentation for Flat Spacer Etching

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Solution Overview

Problem

The free end surface of spacers in liquid crystal panels is not flat due to spherical sliding, leading to abnormal thickness of the liquid crystal box and compromised display quality, as the actual spacer size is smaller than designed, affecting the display quality under temperature and pressure changes.

Innovation Solution

A photomask with a completely transparent region and a shading region is used in the photolithography process, creating regions with different illumination intensities to etch the photoresist material unevenly, resulting in a flatter spacer end surface, improved stability, and matching spacer ratios, thus preventing abnormal thickness and enhancing display quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a conventional photomask with only a completely transparent region is used, then the photoresist material is uniformly exposed, but the spacer end surface becomes spherical due to uniform etching, leading to abnormal liquid crystal box thickness

Engineering Contradiction:

Improveflatness of spacer end surfaceVSAvoidstructure of photomask

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The photomask is segmented into three distinct regions: a completely transparent region (100% light transmittance), a shading region (0-60% light transmittance), and a completely shading region (0% light transmittance). This segmentation creates different illumination intensities in different areas, causing the photoresist material to be etched at different rates. The shading region specifically targets the spherical top portion of the spacer, removing excess material to create a flat end surface while preserving the necessary spacer height and functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the photomask are assigned different light transmittance properties to achieve local quality control in the etching process. The completely transparent region allows full exposure for the base spacer formation, the shading region provides partial exposure to selectively remove the spherical protrusion, and the completely shading region blocks exposure for areas requiring no spacer material. This local differentiation of optical properties enables precise control over the spacer end surface morphology.

Inventive Principle:

Principle #3Local quality

2Reliability

If the spacer end surface is spherical, then the spacer can be formed by conventional photolithography, but the actual spacer size is smaller than designed, affecting the liquid crystal box thickness under temperature and pressure changes

Engineering Contradiction:

Improvestability of spacer under temperature and pressure changesVSAvoidaccuracy of spacer size

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The photomask is designed with predetermined shading regions that pre-calculate and pre-remove the excess spherical material that would otherwise form during conventional photolithography. By performing this material removal in advance during the photolithography exposure step, the spacer end surface is formed flat from the beginning, ensuring that the actual spacer dimensions match the design specifications and maintaining consistent liquid crystal box thickness under various operating conditions.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If the shading region has very low light transmittance (close to 0%), then the spherical surface is effectively removed, but the exposure time or energy required increases

Engineering Contradiction:

Improveflatness of spacer end surfaceVSAvoidexposure time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The shading region is designed with optimized light transmittance parameters ranging from 0% to 60%, allowing adjustment of the etching intensity. By carefully selecting the transmittance value within this range, the photomask achieves effective removal of the spherical surface protrusion while maintaining reasonable exposure times. The parameter optimization balances the competing requirements of sufficient material removal and acceptable process time.

Inventive Principle:

Principle #35Parameter changes

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 solution effectively reduces the spherical surface of the spacer end, stabilizes the spacer, and ensures the correct ratio of main and auxiliary spacers, thereby maintaining the designed thickness and improving the liquid crystal panel's display quality even under external pressure.

Implementation Method 1

Methodology Applied

Scientific EffectPhotolithography: Photopolymerisation

Data Source

PatentUS11137676B2Photomask and exposure system

Publication Date: 2021.10.05 HKC CORP LTD

AI summary

The present application discloses a photomask and an exposure system, the photomask comprising a completely transparent region and a completely shading region disposed around the periphery of the completely transparent region, and a shading region is disposed in the completely transparent region, and a light transmittance of the shading region is defined as T, 0≤T<100%.