Thin Film Transistor Layout Orientation for Anisotropic Substrate Stability
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Solution Overview
Problem
Semiconductor devices fabricated on substrates with anisotropy in thermal shrinkage rate or coefficient of thermal expansion experience adverse effects such as size changes, deformation, and stress due to temperature cycles, affecting device characteristics, particularly when using biaxially stretched thermoplastic resin substrates.
Innovation Solution
The semiconductor device layout is designed such that the direction of thermal shrinkage or expansion is nonparallel or parallel to the current flow direction, optimizing the angle between these directions to minimize the adverse effects and enhance stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a biaxially stretched thermoplastic resin substrate is used, then the substrate is flexible and light-weight, but the thermal shrinkage rate or coefficient of thermal expansion varies in in-plane directions causing anisotropy
Solution Approach 1:
The patent applies asymmetry by deliberately designing the semiconductor device layout to be asymmetric with respect to the substrate's thermal shrinkage directions. The channel length direction is oriented at a specific angle (non-parallel) to the direction of maximum thermal shrinkage, converting the symmetric anisotropic substrate into an asymmetric device configuration that compensates for the thermal distortion.
Solution Approach 2:
The patent changes the geometric parameters of the device layout, specifically the orientation angle between the channel length direction and the thermal shrinkage direction. By optimizing this angular parameter, the device maintains stable electrical characteristics despite the substrate's anisotropic thermal behavior.
2Ease of manufacture
If the substrate undergoes temperature cycles during manufacturing, then high-temperature processes can be completed, but the substrate expands and shrinks due to anisotropy changing device size and characteristics
Solution Approach 1:
The patent implements preliminary action by pre-configuring the device layout orientation before the temperature cycles occur during manufacturing. The channel is deliberately oriented at a specific angle to the thermal shrinkage direction in advance, so that when temperature cycling causes substrate distortion, the pre-positioned device geometry compensates for the dimensional changes.
Solution Approach 2:
The patent applies preliminary anti-action by designing the device geometry to preemptively counteract the expected thermal distortion. The asymmetric orientation creates a geometric compensation effect that opposes the anisotropic shrinkage, preventing characteristic degradation before it occurs during high-temperature processing.
3Device complexity
If the channel direction is parallel to the thermal shrinkage direction, then the layout is simple, but the device characteristics are adversely influenced by size changes and stress
Solution Approach 1:
The patent deliberately introduces asymmetry by orienting the channel at a non-parallel angle to the thermal shrinkage direction. This asymmetric configuration, while slightly increasing layout complexity, ensures that the device characteristics remain stable by geometrically compensating for the anisotropic substrate behavior during temperature cycling.
4Adaptability or versatility
If the substrate size changes due to thermal shrinkage, then the substrate adapts to thermal processing, but the semiconductor device path length and width change affecting performance
Solution Approach 1:
The patent changes the angular parameter of the device layout, orienting the channel at a specific angle to the thermal shrinkage direction. This parameter change creates a geometric relationship where the effective current path length remains stable despite substrate size changes, as the projection of the channel onto the thermal shrinkage axis compensates for the dimensional variations.
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 results in improved uniformity, stability, and increased mobility of the semiconductor device, reducing the sub-threshold slope characteristics and enhancing switching speed, while maintaining the device's original design intent.
Implementation Method 1
the substrate having anisotropy of thermal shrinkage rate or coefficient of thermal expansion in the in-plane directions is expanded and shrunk by the temperature cycle
Implementation Method 2
the substrate having anisotropy of thermal shrinkage rate or coefficient of thermal expansion in the in-plane directions is expanded and shrunk by the temperature cycle
Data Source
AI summary
In the present invention, a thin film transistor is formed on a plastic film substrate (1) having anisotropy of thermal shrinkage rate or coefficient of thermal expansion in in-plane directions of the substrate. A channel is formed such that the direction (7) in which the thermal shrinkage rate or the coefficient of thermal expansion of the substrate is largest is nonparallel to the direction (8) of a current flowing through the channel of the thin film transistor. Then, a thin film transistor having stable and uniform electrical characteristics, which is formed on the plastic film substrate, is provided.