Flexible Substrate Structure for Laser Annealing
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Solution Overview
Problem
The existing transistor fabrication process using organic flexible substrates is limited by their temperature sensitivity, hindering the miniaturization of electronic products due to the need for low-temperature processing and short wavelength lasers, which restricts further reduction in transistor size.
Innovation Solution
A flexible substrate structure comprising a flexible substrate, a first dielectric layer, a metal-containing layer with high reflectivity and heat transfer coefficient, and a second dielectric layer, allowing for long wavelength laser processing such as laser annealing or activation, enabling the formation of small-sized transistors with a channel width and gate length less than 1 um.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a short wavelength laser with low transmittance is used to crystallize semiconductor material on an organic flexible substrate, then the substrate is protected from heat cracking, but the transistor size cannot be further reduced
Solution Approach 1:
An inorganic dielectric layer is introduced as an intermediary between the organic flexible substrate and the semiconductor layer. This inorganic layer has high laser transmittance for long wavelength lasers, allowing the laser energy to reach and crystallize the semiconductor material effectively, while the organic substrate remains protected from direct heat exposure. This mediator enables the use of long wavelength lasers that were previously unsuitable for direct processing of organic substrates.
Solution Approach 2:
The invention changes the laser wavelength parameter from short wavelength (low transmittance) to long wavelength (high transmittance). The inorganic dielectric layer is specifically designed to be highly transmissive to long wavelength lasers, allowing efficient energy coupling to the semiconductor layer while maintaining substrate protection. This parameter change enables better control over the crystallization process and facilitates miniaturization.
2Reliability
If low-temperature and long-time thermal annealing is used for source/drain activation, then the organic substrate is not damaged, but the process time increases and miniaturization is hindered
Solution Approach 1:
The invention replaces the thermal annealing process with laser annealing. Instead of using prolonged thermal treatment, a focused laser beam is used to rapidly heat and activate the source/drain regions. This substitution reduces the processing time significantly while achieving the same activation effect, and the inorganic dielectric layer protects the organic substrate from thermal damage during this rapid heating process.
Solution Approach 2:
The laser annealing process uses pulsed or periodic laser irradiation to activate the source/drain regions. This periodic energy delivery allows precise control over the heating profile, achieving rapid activation without sustained high temperatures that would damage the organic substrate. The pulsed nature of the process reduces overall processing time compared to continuous thermal annealing.
3Length of moving object
If long wavelength laser with high transmittance is used for processing, then miniaturization is enabled, but the organic substrate would be damaged by heat
Solution Approach 1:
The inorganic dielectric layer serves as a thermal mediator that is highly transmissive to long wavelength laser radiation. It allows the laser energy to pass through and reach the semiconductor layer for effective crystallization and activation, while simultaneously providing thermal isolation to protect the organic flexible substrate from heat damage. This mediator enables the use of long wavelength lasers that facilitate miniaturization without compromising substrate integrity.
4Ease of manufacture
If conventional thermal annealing is used, then the process is simple, but the transistor element size cannot be reduced below certain limits
Solution Approach 1:
The invention replaces conventional thermal annealing with laser annealing using long wavelength lasers. This substitution enables precise spatial and temporal control over the heating process, allowing for smaller transistor element sizes to be achieved. The laser can be focused to smaller spots and controlled in pulsed modes, providing the precision needed for miniaturization while maintaining ease of manufacture through a relatively simple process modification.
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 allows for the fabrication of smaller flexible transistors with larger average crystal grain sizes, achieving low impedance source/drain effects and enabling further miniaturization of electronic products beyond conventional thermal annealing limitations.
Implementation Method 1
a short wavelength laser with low transmittance is mostly used to crystallize amorphous or nanocrystalline-phase semiconductor material
Implementation Method 2
The metal-containing layer has a reflectivity greater than 15%
Implementation Method 3
a metal-containing layer having a heat transfer coefficient greater than 2 W/m-K
Implementation Method 4
crystallize amorphous or nanocrystalline-phase semiconductor material on an organic flexible substrate to form a polycrystalline material layer
Implementation Method 5
performing a laser annealing on the amorphous or nanocrystalline-phase semiconductor layer to form a polycrystalline semiconductor layer
Implementation Method 6
the metal-containing layer has a reflectivity greater than 15%... allowing for long wavelength laser processing
Data Source
AI summary
A flexible substrate structure including a flexible substrate, a first dielectric layer, a metal-containing layer and a second dielectric layer is provided. The first dielectric layer is located on the flexible substrate. The metal-containing layer has a reflectivity greater than 15% and a heat transfer coefficient greater than 2 W/m-K. The metal-containing layer is disposed between the first dielectric layer and the second dielectric layer, and the second dielectric layer is an inorganic material layer. A flexible transistor including the above-mentioned flexible substrate structure and a method for fabricating the same are also provided.