Fin-Shaped TFT Channel Layout for Higher Current Without Misalignment
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Solution Overview
Problem
Thin film transistors (TFTs) used in back-end-of-line (BEOL) integration face challenges with small driving currents due to limited contact area between source/drain electrodes and semiconductor channels, and rotating the TFT structure to increase contact area can lead to misalignment issues.
Innovation Solution
The formation of fin-shaped semiconductor channel layers that contact the sidewalls of source and drain electrodes, extending both vertically and horizontally, increases the contact area without increasing the device size and maintains effective alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the TFT structure is rotated to increase contact area between source/drain electrodes and semiconductor channel, then the driving current is improved, but misalignment issues occur between electrodes and channel
Solution Approach 1:
The patent transitions from a planar contact geometry to a three-dimensional fin-shaped channel structure. The fin channel extends vertically from the substrate, allowing source and drain electrodes to contact the channel from the sides rather than from above. This dimensional change increases the contact area between electrodes and channel without requiring rotation of the entire TFT structure, thereby maintaining proper alignment relationships while achieving enhanced driving current.
Solution Approach 2:
The channel is segmented into a fin structure that can be independently formed and positioned. The fin channel is created through selective etching of sacrificial mandrels, allowing precise control over its location and dimensions. This segmentation enables the channel to be positioned exactly where needed to maintain alignment with source and drain electrodes while providing increased side-wall contact area for improved electrical connection.
2Power
If the contact area between source/drain electrodes and semiconductor channel is increased, then the driving current is enhanced, but the device size increases
Solution Approach 1:
The fin-shaped channel structure utilizes the vertical dimension to increase contact area. By extending the channel vertically from the substrate and allowing side-wall contact from source and drain electrodes, the effective contact area is multiplied without expanding the horizontal footprint of the device. This enables enhanced driving current while maintaining a compact device layout suitable for high-density integration.
Solution Approach 2:
The fin channel structure is nested within the device footprint, with the vertical fin extending upward from the substrate plane. The source and drain electrodes wrap around or contact the fin from multiple sides, effectively nesting the contact interfaces within the same horizontal footprint. This nesting approach maximizes contact area within the constrained device area.
Data Source
AI summary
A transistor device including source and drain electrodes, a fin structure extending between and contacting respective sidewalls of the source and drain electrodes, a semiconductor channel layer over the upper surface and side surfaces of the fin structure and including a first and second vertical portions over the side surfaces of the fin structure, and the first and second vertical portions of the semiconductor channel layer both contact the respective sidewalls of the source electrode and the drain electrode, a gate dielectric layer over the semiconductor channel layer, and a gate electrode over the gate dielectric layer. By forming the semiconductor channel layer over a fin structure extending between sidewalls of the source and drain electrodes, a contact area between the semiconductor channel and the source and drain electrodes may be increased, which may provide increased driving current for the transistor device without increasing the device size.