Laser Peeling of Oxide TFTs for Reliable Flexible Devices
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Solution Overview
Problem
Flexible devices, such as those using organic electroluminescent elements, face challenges in achieving high reliability and low-cost manufacturing due to the lower heat resistance of flexible substrates, which limits the improvement of electrical characteristics and reliability of transistors formed directly on these substrates.
Innovation Solution
A peeling method involving the formation of a resin layer with specific thickness and properties over a glass substrate, followed by the formation of transistors using an oxide semiconductor, and subsequent separation and transfer to a flexible substrate using a linear laser device, allowing for lower temperature processing and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transistors are directly formed on flexible substrates, then manufacturing cost is reduced and flexibility is maintained, but electrical characteristics and reliability cannot be improved due to lower heat resistance
Solution Approach 1:
The manufacturing process is segmented into two distinct stages: first forming transistors on a glass substrate (formation substrate) where high-temperature processing can be performed, then transferring the completed transistor assembly to the flexible substrate. This segmentation allows each substrate to be used for its optimal purpose - glass for high-temperature manufacturing, flexible substrate for final flexible device application.
Solution Approach 2:
The glass substrate serves as an intermediary medium that enables high-temperature transistor formation. After transistors are formed on the glass substrate, the entire assembly (glass substrate with transistors) is transferred to the flexible substrate, where the glass substrate acts as a temporary carrier that can withstand the manufacturing temperatures required for high-quality transistor formation.
2Reliability
If transistors are formed on glass substrates and then transferred to flexible substrates, then electrical characteristics and reliability are improved, but manufacturing complexity increases
Solution Approach 1:
Transistors are preliminarily formed on the glass substrate with all necessary high-temperature processing steps completed before transfer. This preliminary action on the formation substrate simplifies the overall process by consolidating complex manufacturing steps in one location before the transfer operation.
Solution Approach 2:
The transistor assembly is extracted from the glass substrate as a complete unit and transferred to the flexible substrate. This extraction approach simplifies the transfer process by moving a pre-assembled functional unit rather than attempting to transfer individual components separately.
3Productivity
If conventional peeling methods are used, then transfer to flexible substrate is achieved, but manufacturing cost increases and mass productivity is reduced
Solution Approach 1:
The conventional mechanical peeling method is replaced with laser beam irradiation. The laser beam provides localized heating that enables controlled peeling of the transistor assembly from the glass substrate without requiring mechanical force, thereby simplifying the transfer process and improving mass productivity.
Solution Approach 2:
The laser beam irradiation induces localized phase transitions (heating and melting) in the resin layer, enabling controlled peeling. This phase transition approach allows for precise, localized separation without affecting the surrounding areas, improving both cost-effectiveness and productivity.
4Area of stationary object
If large-sized substrates are used, then device area is increased, but handling and processing difficulty increases
Solution Approach 1:
Laser beam irradiation replaces mechanical handling methods for peeling and transfer operations. This allows large-sized substrates to be processed without requiring complex mechanical support structures or multiple handling steps, as the laser can precisely target and peel specific regions regardless of substrate size.
Solution Approach 2:
The laser beam irradiation provides localized processing, where only the specific region requiring peeling is affected. This local quality approach allows large substrates to be processed in targeted areas without compromising the entire substrate, maintaining ease of operation even with large device areas.
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 method enables the production of highly reliable, flexible devices with improved electrical characteristics at lower temperatures and reduced costs, while allowing for the use of large-sized substrates and simplified manufacturing processes.
Implementation Method 1
a step of irradiating the resin layer with light using a linear laser device
Implementation Method 2
irradiating the resin layer with light using a linear laser device
Data Source
AI summary
A peeling method at low cost with high mass productivity is provided. A resin layer having a thickness greater than or equal to 0.1 μm and less than or equal to 3 μm is formed over a formation substrate using a photosensitive and thermosetting material, a transistor including an oxide semiconductor in a channel formation region is formed over the resin layer, the resin layer is irradiated with light using a linear laser device, and the transistor and the formation substrate are separated from each other. A first region and a second region which is thinner than the first region or an opening can be formed in the resin layer. In the case of forming a conductive layer functioning as an external connection terminal or the like to overlap with the second region or the opening of the resin layer, the conductive layer is exposed.