Planarization Film Height Control for Display Spacer Precision
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Solution Overview
Problem
The use of grayscale masks in photolithography for forming spacers in display devices can lead to thermal sagging of photosensitive materials, resulting in spacers with variable heights and reduced precision, which complicates the manufacturing process.
Innovation Solution
A display device structure and manufacturing method involving a planarization film with first and second flat portions and contact holes, where the first electrodes are exposed in openings, and the second flat portions are located between these openings, allowing for precise control of spacer heights using a grayscale mask in a single photolithography exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If grayscale masks are used in photolithography to form spacers and other structural elements in a single process, then manufacturing efficiency is improved, but thermal sagging of photosensitive material occurs causing spacer height precision to deteriorate
Solution Approach 1:
The planarization film is segmented into first flat portions (overlapping openings) and second flat portions (between openings) with different heights. This segmentation allows different regions to serve different functions: first flat portions provide support to reduce thermal sagging, while second flat portions form the actual spacers with precise height control.
Solution Approach 2:
Different regions of the planarization film are given different local properties through the grayscale mask exposure. The first flat portions have higher light transmission to create thinner regions, while the second flat portions have lower light transmission to create thicker regions. This local differentiation enables precise height control in spacer regions while maintaining structural support in other areas.
2Ease of manufacture
If photosensitive material with large volume is used to form spacers, then spacer formation is achieved, but thermal sagging increases causing height variability to worsen
Solution Approach 1:
The planarization film is formed in advance with predetermined first flat portions and second flat portions at different heights before the actual spacer formation process. This preliminary structuring provides a stable foundation that prevents thermal sagging during subsequent processing, ensuring uniform spacer heights without requiring excessive photosensitive material volume.
3Ease of operation
If openings are placed close to spacers to expose first electrodes, then electrode exposure is achieved, but thermal sagging of photosensitive material near openings causes spacer height precision to deteriorate
Solution Approach 1:
The planarization film provides localized height differentiation: first flat portions directly overlap the openings to provide structural support and prevent thermal sagging, while second flat portions are positioned between openings to form spacers with precise height control. This local quality differentiation allows openings to be placed close to spacers without compromising spacer height precision.
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 enhances the precision of spacer heights and reduces thermal sagging, improving the yield of display devices while maintaining the use of grayscale masks in photolithography.
Implementation Method 1
forming the planarization film by photolithography using a grayscale mask and involving a single exposure
Data Source
AI summary
The disclosure has an object to achieve a high level of height precision for spacers on a back plane. A display device includes: edge covers having a plurality of openings in which first electrodes are exposed; and a planarization film having first flat portions, second flat portions, and contact holes. The plurality of openings respectively overlap the first flat portions in a plan view. The second flat portions are located between the plurality of openings in a plan view. Each edge cover overlapping one of the first flat portions in a plan view has, on a second electrode side, a surface that has a first height from a bottom surface of the planarization film on a substrate side. Each second flat portion has, on the second electrode side, a surface that has a second height from the bottom surface. The first height is smaller than the second height.