Segmented Underlying Insulation Film for Flexible TFT Stress Relief
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Solution Overview
Problem
The flexibility difference between underlying insulation films and thin-film transistors on flexible substrates leads to cracking under mechanical or thermal stress, deteriorating device characteristics.
Innovation Solution
The underlying insulation film is patterned in separate areas over the substrate, with semiconductor films and gate electrodes, reducing stress concentration and preventing cracks, while maintaining sufficient thickness for adhesion and insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an underlying insulation film is formed over the entire surface of a flexible substrate, then adhesion and insulation are improved, but the film cracks under mechanical or thermal stress due to flexibility mismatch
Solution Approach 1:
The underlying insulation film is divided into multiple separate regions, each positioned beneath individual semiconductor films or transistor structures. This segmentation allows each film region to independently adhere to the flexible substrate without creating continuous stress paths, thereby preventing cracks while maintaining sufficient adhesion and insulation where needed.
Solution Approach 2:
The insulation film is selectively formed only in specific locations beneath semiconductor films or transistor structures rather than covering the entire substrate. This local quality approach provides adhesion and insulation precisely where required while leaving gaps in regions where stress accumulation would occur, thus resolving the contradiction between needing coverage and avoiding cracks.
2Area of stationary object
If an underlying insulation film is formed over the entire surface, then complete coverage is achieved, but device characteristics deteriorate due to cracking
Solution Approach 1:
The insulation film coverage is segmented into discrete regions rather than continuous coverage. Each segment is positioned to provide necessary insulation beneath active device structures while gaps between segments prevent stress-induced cracking, thereby maintaining device characteristics without sacrificing complete functional coverage.
Solution Approach 2:
The insulation film is applied with local quality - present where needed for electrical insulation and structural support beneath semiconductor films, and absent in regions where its presence would cause cracking. This selective formation maintains device characteristics while avoiding the harmful effects of continuous coverage.
3Strength
If the underlying insulation film is made thin to reduce stress, then flexibility is improved, but adhesion and insulation performance decrease
Solution Approach 1:
The insulation film is segmented into separate regions that can be optimized for both thickness and performance. Each segment can be sufficiently thin to allow substrate flexibility while maintaining adequate adhesion and insulation locally where device structures are present, avoiding the need for continuous thick coverage that would restrict flexibility.
Solution Approach 2:
The film thickness and presence are optimized with local quality - thin or absent in regions where flexibility is prioritized, and sufficiently thick where adhesion and insulation are critical for device operation. This spatial variation resolves the contradiction between flexibility and performance.
Data Source
AI summary
The invention provides, as an aspect thereof, a semiconductor device that includes: a substrate; an underlying insulation film that is formed over the substrate; and a plurality of thin-film transistors that is formed over the underlying insulation film, each of the plurality of thin-film transistors having a semiconductor film, wherein the underlying insulation film is formed in separate areas each of which includes, when viewed in plan, at least one of the plurality of semiconductor films.